Grid Connected PV System
A grid connected PV system is one where the photovoltaic panels or array are connected to the utility grid through a power inverter unit allowing them to operate in parallel with the electric utility grid.
In the previous tutorial we looked at how a stand alone PV system uses photovoltaic panels and deep cycle batteries to store its solar energy providing a complete self-contained solar power system. However, this type of solar system works fine providing there is enough solar radiation during the day to recharge the batteries for use during the night.
Stand alone solar systems are self contained fixed or portable solar PV systems that are not connected to any local utility or mains electrical grid as they are generally used in remote and rural areas. This generally means that the electrical appliances are a long way from the nearest fixed electrical supply, or were the cost of extending a power line from the local grid may be very expensive.
In recent years, however, the number of solar powered homes connected to the local electricity grid has increased dramatically. These Grid Connected PV Systems have solar panels that provide some or even most of their power needs during the day time, while still being connected to the local electrical grid network during the night time.
Solar powered PV systems can sometimes produce more electricity than is actually needed or consumed, especially during the long hot summer months. This extra or surplus electricity is either stored in batteries or as in most grid connected PV systems, fed directly back into the electrical grid network.
In other words, homes and buildings that use a grid connected PV system can use a portion or all of their energy needs with solar energy, and still use power from the normal electrical mains grid during the night or on cloudy dull and rainy days, giving the best of both worlds. Then in grid connected PV systems, electricity flows back-and-forth to and from the mains grid according to sunlight conditions and the actual electrical demand at that time.
In a grid connected PV system, also known as a “grid-tied”, or “on-grid” solar system, the PV solar panels or array are electrically connected or “tied” to the local mains electricity grid which feeds electrical energy back into the grid.
The main advantage of a grid connected PV system is its simplicity, relatively low operating and maintenance costs as well as reduced electricity bills. The disadvantage however is that a sufficient number of solar panels need to be installed to generate the required amount of excess power.
Since grid tied systems feed their solar energy directly back into the grid, expensive back-up batteries are not necessary and can be omitted from most grid connected designs. Also, as this type of PV system is permanently connected to the grid, solar energy consumption and solar panel sizing calculations are not required, giving a large range of options allowing for a system as small as 1.0kWh on the roof to help reduce your electricity bills, or a much larger floor mounted array that is large enough to virtually eliminate your electricity bills completely.
Grid Connected Net Metering
Connecting solar panels together to make larger array’s for connecting directly to the local power grid enables you to engage in one of the most advantageous parts of generating your own electricity: Net Metering or Net Billing. If during a sunny day more electricity is produced by your solar PV system then you use or consume, this excess solar power is delivered back to the utility grid with the effect of rotating your electric meter backwards. When this happens you will normally be given credits by the local power company for the amounts of electricity produced by your grid connected PV system.
If during the billing period you use or consume more electrical energy than you generate, you are billed for the “net amount” of electricity consumed as you would be normally. If, however, you generate more solar energy than you consume, you are credited for the “net amount” of electricity generated which may be either a reduction in your monthly electricity bill or a positive repayment directly to you or the account holder.
When installing a PV system, if net metering is available by your local electricity company, you may be required to install a new second electrical meter instead of using a single electricity meter that spins in both directions. This new meter allows for a measurement of net energy consumption, both entering and leaving the system and would be used to reduce your electricity bill. However, each electrical utility company has its own policy regarding the buying back of energy generated by your own small solar power station.
While net metering is the ideal way to resell your solar generated excess power, some companies buy-back energy at a lower wholesale rate than the electricity you consume from the same power company. This means that you may need to generate more solar power than you would normally consume just to break even.
Simplified Grid Connected PV System
Grid connected PV systems always have a connection to the public electricity grid via a suitable inverter because a photovoltaic panel or array (multiple PV panels) only deliver DC power. As well as the solar panels, the additional components that make up a grid connected PV system compared to a stand alone PV system are:
- Inverter – The inverter is the most important part of any grid connected system. The inverter extracts as much DC (direct current) electricity as possible from the PV array and converts it into clean mains AC (alternating current) electricity at the right voltage and frequency for feeding into the grid or for supplying domestic loads. It is important to choose the best quality inverter possible for the budget allowed as the main considerations in grid connected inverter choice are: Power – Maximum high and low voltage power the inverter can handle and Efficiency – How efficiently does the inverter convert solar power to AC power.
- Electricity Meter – The electricity meter also called a Kilowatt hour (kWh) meter is used to record the flow of electricity to and from the grid. Twin kWh meters can be used, one to indicate the electrical energy being consumed and the other to record the solar electricity being sent to the grid. A single bidirectional kWh meter can also be used to indicate the net amount of electricity taken from the grid. A grid connected PV system will slow down or halt the aluminium disc in the electric meter and may cause it to spin backwards. This is generally referred to as net metering.
- AC Breaker Panel and Fuses – The breaker panel or fuse box is the normal type of fuse box provided with a domestic electricity supply and installation with the exception of additional breakers for inverter and/or filter connections.
- Safety Switches and Cabling – A photovoltaic array will always produce a voltage output in sunlight so it must be possible to disconnect it from the inverter for maintenance or testing. Isolator switches rated for the maximum DC voltage and current of the array and inverter safety switches must be provided separately with easy access to disconnect the system. Other safety features demanded by the electrical company may include earthing and fuses. The electrical cables used to connect the various components must also be correctly rated and sized.
- The Electricity Grid – Finally the electricity grid itself to connect too, because without the utility grid it is not a Grid Connected PV System.
An grid connected system without batteries are the simplest and cheapest solar power setup available, and by not having to charge and maintain batteries they are also more efficient. It is important to note that a grid connected solar power system is not an independent power source unlike a stand alone system. Should the mains supply from the electrical grid be interrupted, the lights may go out, even if the sun is shining. One way to overcome this is to have some form of short term energy storage built into the design.
Grid Connected System with Batteries
A small scale photovoltaic solar system that has storage batteries within its design, also operates in conjunction with the local electricity company. The short-term peak demand is met by the battery without drawing from the grid and paying the extra charge.
When used in grid connected PV systems, storage batteries can be classified into short term storage for a few hours or days to cover periods of bad weather and long term storage over several weeks to compensate for seasonal variations in the solar irradiation between the summer and winter months.
Incorporating batteries into a grid connected system requires more components, is more expensive, and lowers the systems overall efficiency. But for many homeowners in remote areas who regularly experience a loss of their grid supply during bad weather conditions or have critical electrical loads that can not be interrupted, having some form of backup energy storage within their grid connected system can be a great benefit.
Grid Connected PV System with Battery Storage
So we can see from above, that a PV system with battery storage is basically the same as for the previous grid connected PV system with the addition of the batteries and charge controller. The battery charge controller, determines whether the power generated by the solar panels is needed for home use, to run low voltage equipment and lighting or whether it will charge the deep-cycle backup batteries to be used later on.
The DC current leaving the controller passes through the DC to AC inverter, transforming it into electricity usable by general household appliances. Any surplus electricity not being consumed or used by the home can be sent to the electricity companies power grid. It is better to run DC rated lighting and appliances first directly off your solar system before the current is converted to AC from the inverter. This will gain the most efficiency.
Living with a grid connected solar PV system is no different than living with just the normal grid power, except that some or all of the electricity that is consumed comes from the sun. PV solar systems designed for grid connection are usually designed to meet at least half of a homeowners electrical needs.
Purchasing a home solar photovoltaic panel array large enough to supply the entire electrical needs of a home would be extremely expensive with the solar array taking up a large amount of space. The solar power generated by a grid connected system is therefore only partial, with the remaining energy being made up by the power company.
The advantage of a Grid Connected PV System, either with or without storage batteries is that on clear blue sunny days, when the photovoltaic system is producing large amounts of current and the home is consuming low energy levels, for example, if you are out of your home all the day working, you’re solar system keeps generating electricity.
The excess electricity generated does not go to waste but is fed back into the power grid to be used by your neighbouring homes who unknowingly end up using the clean, renewable energy themselves while making money for you through your “net metering” arrangement.
In the next tutorial about “Solar Power”, we will see that a Solar Inverter can be used to transform the DC voltages and currents of a typical solar panel into an alternating AC voltage suitable for feeding directly into the power grid.
Introduction: Arduino Based Solar PV Energy Meter With Xively Connectivity ( Can Be Monitored on Android or iPhone )
It’s been about two days since I made The Arduino PV generation Meter, but it was a mistake to not to take the step by step photos before proceeding for final testing. And it was an awful idea to show the raw box of so called energy meter :P. Anyways, It was really fun to work on arduino and for the first time. This tutorial is based on the original instructable by Deba18. I made few tweaks and enhanced the code little bit.
What this meter do?
- Sense the Solar Panel Voltage
- Sense amperage of Solar Panel
- Calculates energy used
- Display output live on 16×2 Character LCD
- and post it to Xively (www.xively.com)
E.g in my case, am uploading data to xively from PV energy meter and grabing data for pvoutput.org
So the Energy Consumption of my home is measured by Current Cost Energy Meter and Solar PV generation measured by My Homemade Arduino Solar PV Meter.
Here is everything you will need for this easy to build project:
- Arduino UNO R3
- Network Shield
- ACS712 Current Sensor (30A)
- 16×2 Character LCD
- Jumper Wires (male to male and male to female)
- 100K resistor
- 10k resistor
- 5k potentiometer
- Connection sockets
- Breadboard (optional)
Step 2: Understanding Terms and Calculating Values
What is power?
Power is a product of voltage (volt) and current (Amp)
P=VxI Unit of power is Watt or KW
What is Energy?
Energy is product of power (watt) and time (Hour)
Unit of Energy is Watt Hour or Kilowatt Hour (kWh)
We need voltage, current and time in our project.
Step 3: Measuring Voltage
To measure Voltage, we will need:
- An Arduino
- The Arduino IDE (integrated development environment).
- One 100Ko resistor.
- One 10Ko resistor.
- Four wires, in at least two different colors (red and black are recommended).
- A breadboard (or suitable stripboard and soldering equipment).
The Arduino Sketch
To eliminate the possibility that the Arduino will run a previous sketch and operate in an unknown way, you can program the sketch first.
To create the voltmeter sketch:
Open the Arduino IDE.Paste in the following code:
float vPow = 4.7; float r1 = 100000; float r2 = 10000; void setup Serial.begin(9600); // Send ANSI terminal codes Serial.print(\x1B); Serial.print([2J); Serial.print(\x1B); Serial.println([H); // End ANSI terminal codes Serial.println; Serial.println(DC VOLTMETER); Serial.print(Maximum Voltage: ); Serial.print((int)(vPow / (r2 / (r1 r2)))); Serial.println(V); Serial.println; Serial.println; delay(2000); void loop float v = (analogRead(0) vPow) / 1024.0; float v2 = v / (r2 / (r1 r2)); // Send ANSI terminal codes Serial.print(\x1B); Serial.print([1A); // End ANSI terminal codes Serial.println(v2);
And then save the sketch:
On the File menu, click Save As…This sketch begins by initializing the serial port and declaring a few variables: vPow – When powered over a USB cable, it is common for the Arduino’s 5V power supply to be a little less than that ideal.
r1 – the value (in ohms) of the first resistor in the circuit.
r2 – the value (in ohms) of the second resistor in the circuit.
The sketch then sends some basic information to the terminal, and it displays the maximum voltage than can safely be measured by the current circuit.
The Serial Port Monitor in the IDE can be used to view the messages sent by this sketch.
The serial port you need to connect to can be found from the Arduino IDE: On the Tools menu, click Serial Port and look for the item that is ticked.The other setting you should use are:
Hardware Flow Control: None
Software Flow Control: None
Step 4: Building the Circuit
Disconnect the Arduino from your computer before building this circuit!
The circuit can be constructed on a breadboard:
The analog inputs of an Arduino can measure up to 5V (when using the built-in analog reference voltage). Even when only connecting to a 5V circuit, you should use the resistors to help protect the Arduino from short-circuits or unexpected voltage surges.
Those two resistors form a potential divider that is used to lower the voltage being measured to a level that the Arduino can read. This actually extends the range that can be used. For example, if resistors are used to halve the input voltage then the Arduino can effectively read up to 10V (since 10V will be read as 5V, 5V will be read as 2.5V…). This comes at the expensive of accuracy – the ADCs in the Arduino can read up to 1024 different levels between 0V and 5V. By expanding the range to 10V, those 1024 levels are spread across a wider range and are therefore less able to detect small changes.
You can increase the resistance value of R2, then the maximum voltage that can be read will be decreased; giving a slightly more accurate reading. With R1 at 100Ko and R2 at 10Ko, the input voltage is reduced by a factor of around 11 – allowing the voltmeter to read from 0V–55V.
The formula for calculating values in a potential divider is:
If the divider for the Arduino voltmeter is functioning correctly then Vout will be a maximum of 5V, and so you can calculate the maximum input voltage to the circuit:
You can see a variation of this expression used in the setup routine of the sketch.
Note: If you use different resistors from the ones suggested here, you must be remember to adjust the values of r1 and r2 in the sketch.
When measuring the voltage in the loop routine, analogRead(0) is used to read the level from analog input 0. The returned value is an integer in the range 0 through 1023, so it must first be adjusted to a range 0 through 5. This is done by multiplying it by the power supply level, and then dividing by 1024.
To transform the 0V–5V value into a reading that reflects the range of values that can be measured by the circuit, the resistors must be taken into account in the same way as was done to calculate the maximum voltage the circuit could measure:
Step 5: Current Measurment
For current measurement we will use a Hall Effect current sensor ACS 712 (30 A).
WORKING PRINCIPLE :
The Hall Effect is the production of a voltage difference (the Hall voltage) across an electrical conductor, transverse to an electric current in the conductor and a magnetic field perpendicular to the current.
The data sheet of ACS 712 sensor is found online easily.
From Data Sheet of ACS 712, it measure positive and negative 30Amps, corresponding to the analog output 66mV/A.
No test current through the output voltage is:
Analog read produces a value of 0-1023, equating to 0v to 5v
So, Analog read 1 = (5/1024) V =4.89mv
Value = (4.89Analog Read value)/1000 V
But as per data sheets offset is 2.5V (When current zero you will get 2.5V from the sensor’s output)
Current in amp =actual value10
Step 6: Time Measurement
For time measurement there is no need of any external hardware, as ARDUINO itself has inbuilt timer. The millis function returns the no of milliseconds since the Arduino board began running the current program.
Step 7: Connect LCD
Connect LCD with ARDUINO as given bellow :
VO. Arduino GND pin Resistor or Potentiometer
D0. Arduino. Not Connected
D1. Arduino. Not Connected
D2. Arduino. Not Connected
D3. Arduino. Not Connected
A. Arduino Pin 13 Resistor (Backlight power)
K. Arduino GND (Backlight ground)
Step 8: Data Uploading to Xively.com
For data uploading to xively.com the following library to be downloaded first
SPI : Import from arduino IDE (sketch. Import library. )
Ethernet : Import from arduino IDE ((sketch. Import library. )
And add your device by folloqing xively instructions (Really Easy)
I am creating a detailed video.
Feel free to ask anything if you have any difficulties.
Step 9: Packing Up Your Circuits
You can use any thing to manage and install your circuit in it. I used an old DSL router of Orange. Got it from garbage store :P.
I removed main board from the casing of Orange DSL Router. and modified it accordingly.
Step 11: Checking My Working Solar Meter
This video was made when there was power cut down from grid station. So its showing 000V in AC in.
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Комментарии и мнения владельцев
Hi, I would like to display it on an i2c LCD instead of a normal 16×2 LCD, would you know how I can change the code? Thanks a lot!
Thank you for sharing your project! Nice work!
Would you like to make a project to me ?
Hi. I would like to try this project, however in the video, what are those things that you connected the projected to? asdie from router?
which things? can you please tell me?
Just a short HW related question: how did you manage to connect the thick wires to the ACS712?
Are they soldered on the backside?
I have a 30 Amps sensor but it has the same thin connectors as the 5 Amps version.
I just soldered them at backside by scratching coat on copper terminals. Solder your thick wires on copper terminals hardly with enough soldering wire. How much current you are planning to measure? I would like to see what you are going to make ^_^
less then 24 Amps. This is when all my biggest power consumers are running together (almost never).
I plan to measure my net consumption/production and upload it to pvoutput.org
Thats great. Feel free to ask any help 🙂
🙂 Thanks. May be I will get back to you. 🙂
Hello I’m trying to measure the ac current using interface between LPC2148 and ACS712. but im not able to get a correct readings. can u please help??
I don’t have any experience working with LPC2148. But if you want to measure AC current using ACS712 in arduino, i can help you with the sketch. Also, Please make it sure you use correct wire and insulate module to measure AC current.
hi. i have to compare DC voltage and current of two solar modules. Can I do this with this arrangement? can I use two analogs i/p of Arduino for two voltage source grounding both negative terminal?since there is only 6 analogs i/p terminal and for comparison there is need of 8 i/p(2 for foltage 2 for current for both modules).
Its really easy. You don’t need any extra thing. Just get the readings on two pins. E.g
1st voltage positive wire with voltage divider on pin A12nd voltage positive wire with voltage divider on pin A2
calibrate pins with your voltages and write proper script 🙂
Looks interesting, thanks. Will play around with your Instructable.
I am uploading few steps and pictures to show what its looking as a final Product 🙂
What is net metering and how does it work?
When grid-tied solar panels make more energy than a customer needs, the excess is sent back to the electric grid along the same wires that carry power to the home when the sun is down.
Net metering is the utility billing practice of recording the excess energy generated by a solar installation and applying it to the customer’s bill as credit toward energy drawn from the grid.
It’s a pretty straightforward way to compensate solar panel owners for their contributions, and it’s been the law in many places across the United States for years. But like anything that involves utility companies or the law, there are nuances and complications that creep into the picture when you look a little deeper. And many states are starting to move away from net metering as the economics of participating in the grid get increasingly complicated.
Here’s our guide to net metering, including how it works, where it’s available, the benefits and drawbacks, and alternative billing programs.
See how many solar panels you would need to offset your electricity bill
- Net metering ensures that every kilowatt-hour (kWh) of energy a homeowner’s solar panels produce goes toward reducing their utility bills by the same amount.
- Programs differ in how long credits are allowed to roll over and how much value each credit has.
- The benefits of net metering include good financial return on an investment in solar panels, simple billing arrangements, environmental benefits, and reduced costs of infrastructure and fossil fuel power plants.
- Some utilities claim that net metering causes a “cost shift” as wealthy homeowners reduce the amount their pay for the grid while low-income customers bear more of the cost but this argument has been advanced largely by the utility companies themselves, who profit from expanding and maintaining control of grid infrastructure.
- Many states have moved away from net metering in recent years, replacing it with net billing that offers lower credits for all kWh sent to the grid from solar owners’ systems.
How net metering works
The type of net metering described above is the simplest example of the practice, and is also called “true net metering” or “1-for-1 net metering,” because the utility offers credit for each kilowatt-hour (kWh) of electricity sent to the grid, which can be redeemed toward a kWh used when the sun isn’t shining.
When a homeowner gets a solar energy system installed, the utility replaces their electric meter with a new bi-directional meter, which can record energy the solar panels export to the grid and energy the customer takes from the grid when the solar panels aren’t making enough power to run the home’s appliances.
At the end of each billing period, the utility totals up the energy that was sent to the grid and energy used from the grid. If the homeowner used more electricity than they sent, the utility bills them for the difference. If they sent more than they used, the utility records a credit balance that will be applied to the next monthly bill.
Here’s a graphical representation of how that works, with an increasing credit during the daylight hours that gets used up over the course of the night:
Not all net metering programs work in exactly the same way. Differences between net metering programs include:
- Credit rollover (monthly vs. annual vs. indefinite)
- Value of credits
- Time of use rates
Under most net metering programs, kWh credits carry over from month to month, meaning credit for energy generated in sunny summer months can be used toward energy a customer purchases in darker winter months.
Some utilities allow these credits to carry over indefinitely, but most reconcile any credits that remain at the end of a 12-month period and pay the customer for them at a close-to-wholesale rate. This is called the “true-up date,” and it is generally set as the date a customer’s solar panels were given permission to operate (PTO) interconnected with the grid.
Some utilities allow solar customers to select their annual true-up date, while others set one date for all customers, which is usually in the late spring to give solar owners the best chance of using up any banked credits from the previous year before the next sunny season.
There are also places where net metering credits are reconciled every month. Any excess energy credits left at the end of each billing cycle are paid to the solar system owner, usually at a greatly reduced rate close to the wholesale price of energy. This reduces the financial benefits of net metering, and homeowners in these places may choose to design a solar system that won’t exceed their total usage in sunny months.
Value of credits
Under true net metering, each kWh credit represents a kWh, and they can be redeemed for energy from the grid at any time. But some net metering programs provide a monetary bill credit instead. That credit can be exactly equal to the retail value of a kWh, but sometimes it can be less.
For example, under Net Energy Metering (NEM) 2.0 in California, the energy credits are worth just a small fraction less than the retail rate because of non-bypassable charges, which are portions of the retail cost of energy that go toward low-income and environmental programs.
Time of use rates
Some utilities offer time of use (TOU) rate plans, under which the cost of energy changes depending on the time it is used. Peak demand on the grid usually occurs in the evening on weekdays, when most people return home from work and begin using their appliances. During these times, the cost of energy increases.
TOU rate plans have at least two different rates for on-peak and off-peak times. Solar panel owners on TOU rates get credit for the electricity their panels send to the grid during the time period it is generated.
So for example, say a solar installation sends 10 kWh to the grid during the off-peak period when energy is 0.10/kWh. The owner would earn a 1 credit for that energy. If energy from the grid is worth 0.15/kWh during peak times, the credit they earned would only be able to offset about 6.7 kWh worth of peak-time electricity.
Because of the varying value of energy, TOU rates can make a home solar battery more financially beneficial. Homeowners can charge their battery with solar energy during the day, and use the stored energy in the battery to avoid paying peak energy in the evening.
Benefits of net metering
There are many benefits of net metering, some of which go to the solar system owner and some of which go to the grid and society as a whole. Here’s a list of some of the benefits:
- Makes solar more financially viable for homeowners
- Provides a simple way to credit solar owners for the energy their systems produce
- Encourages new solar development on existing structures, reducing carbon emissions and leaving existing undeveloped land untouched
- Reduces the need for new fossil fuel power plants
- Reduces the need for new power transmission infrastructure, which is expensive, controversial, and takes years to approve, fund, and build
- Virtual net metering makes the benefits of solar available to people who don’t own their homes
Drawbacks and controversy
As solar advocates, we’d love to tell you that there are no drawbacks to net metering, but that wouldn’t necessarily be true. Studies have shown that solar is a net benefit to the grid when there is a small number of net metered systems interconnected, but things get more complicated once net metering hits a threshold of around 5% to 10% of peak demand.
Here are some of the drawbacks of net metering:
- Without time of use billing, the value of net metering credits isn’t adjusted based on the time it’s produced.
- Too many net metered solar installations reduce demand on the grid during the daytime, but don’t alleviate problems at peak evening times as the sun is setting.
- When there are a lot of solar installations in a small area, the distribution grid sometimes needs to be upgraded to handle higher levels of the two-way flow of power, potentially costing all ratepayers more (although the cost often falls on the owner of the system that will cause the distribution system infrastructure to exceed its rated capacity).
- Some utility companies claim that net metering represents a “cost shift” from wealthier people to lower-income people, because wealthier people can install solar panels and reduce their energy bills down to almost nothing, leaving people without solar to pay an increased share of the fixed costs of maintaining the grid.
The effects of the alleged “cost shift” are difficult to fully understand, because the argument that a cost shift exists is mainly advanced by electric utility companies themselves. Over the past ten years or so, utility companies around the country have pushed the cost shift narrative as a way to end net metering.
Often, these companies are simply trying to kill rooftop solar, and not trying to build a system that works to reduce bills for their ratepayers. They don’t attempt to offer a reasonable successor program that recognizes the full financial, environmental, and social benefits of solar to the grid, or they spend millions of dollars (sometimes ratepayer dollars) to lobby lawmakers and public utilities commissioners to ignore many of those benefits.
Alternatives to net metering
There are a few different net metering alternatives in place around the U.S., including net billing, feed-in tariffs, and buy-all, sell-all. States like Arizona and California used to have net metering but have since moved to so-called “successor” programs, while other states never had good policies to begin with.
Here’s a rundown of some net metering alternatives:
Under net billing, solar energy that is used to power the home’s appliances directly reduces the homeowner’s electric bill by the full retail cost of electricity, but energy that is sent to the grid is credited at a lower rate. The monetary credits are applied toward the customer’s bill, but don’t usually equal the cost of the electricity the customer pulls from the grid when their solar panels aren’t producing energy.
Net billing is often combined with TOU billing, and the credits paid to solar owners for energy sent during the sunniest parts of the day are often very low, while the energy they have to buy from the grid in the evening is priced very high. Because of this, net billing encourages solar owners to add batteries to their systems, storing the solar energy instead of selling it for pennies on the dollar, and then using it in the evening instead of buying on-peak power from the utility.
California’s net billing is the most infamous example of this type of solar metering. In late 2022, the California Public Utilities Commission handed down a decision to switch the state away from its modified net metering system. The new Net Billing tariff has different payments for solar energy for each hour of the day, every day of the year, which change on a monthly basis. Many times during the year, the value of exported solar energy is almost 0.
In a sort-of worst case scenario for home solar, you may be required to engage in “buy-all, sell-all” also known as “parallel operation” with the utility grid. “Buy-all, sell-all” means you buy all the energy you need from the utility company and send all the solar energy your system produces to the grid.
The price paid for solar energy under a buy-all, sell-all program is called the feed-in tariff. These programs usually pay a low price for every kWh of solar energy, compared to the price at which the utility sells electricity to residential customers.
Thankfully, there are very few places where solar owners are required to engage in buy-all, sell-all programs.
Utility customers in many places can set up a special solar installation called a “non-export system.” That means you have to either use, store, or lose the solar power so it doesn’t get sent to the grid.
With a non-export system, you have to try to maximize your use of solar energy by installing batteries to store the excess electricity and reverse-power protection devices to prevent exporting power. You can still get power from the grid when you need it, too.
This type of system can get quite complicated, and when installed on a home with a grid connection, you’ll still need to notify your utility and likely pay an interconnection fee and/or other fees that the utility charges to ensure your system can be safely installed.
Which states have net metering?
The number of states with true net metering has decreased over the past several years. The map below shows the states that offer true net metering, modified net metering, net billing, or no net metering, as of June 2023.
Three states are ending their net metering programs soon, and homeowners in these places may want to get solar panels soon. Here’s a rundown of the deadlines:
- Idaho Power customers who install new solar panel systems are subject to changing rules, as the state Public Utilities Commission is in the process of allowing the company to offer decreased compensation for excess generation.
- People in Arkansas will need to have solar panels installed by Sept. 30, 2024 to qualify for net metering.
- After July of 2023, Duke Energy customers in North Carolina will no longer be eligible for net metering, but will be able to sign up for a somewhat similar “bridge rate” if they get solar panels installed by the end of 2026.
Bottom line: why does net metering matter?
Net metering policies across the U.S. have been the single best incentive to get ordinary people to invest in renewable energy generation systems. Thanks to net metering rules, people all across the country can generate their own electricity and contribute to fighting climate change.
As the grid becomes more modernized and decarbonized, distributed generation assets like solar panels, batteries, and electric vehicles will become much more important, providing value to both system owners and the grid as a whole.
How To Read Solar Panel Meter (Do This)
A solar energy system is made up of more than simply solar panels. Without other components, this system wouldn’t be able to offer you free power. A solar system’s meters, in particular, are frequently ignored.
Here’s What You’ll Be Learning:
- What Solar Meters Are
- How Solar Meters Work
- How To Read Solar Meters
- What Net Metering Is
- Benefits of Solar Meters
We aim to give solar meters their due in this article and talk about how you can read them.
What Are Solar Meters?
Solar meters are your link to your solar investment. They can tell you how much power your system produces, how much energy you use, and how much energy you still have to buy from the utility.
A solar meter is basically a device that measures solar power or sunshine in W/m 2 and may be used to check the effectiveness of Windows or to install solar power equipment.
To monitor and assess PV plant performance, solar meters collect PV yield output and local energy usage. It frequently includes a monitoring feature that alerts plant owners to concerns with PV plant performance, allowing them to swiftly fix issues and optimize return on investment.
What is the Role Of Meters In Surplus Energy Production?
Energy is supplied to the grid in return for credits when solar panels create more electricity than is required. Then, when solar panels are underperforming at night or on cloudy days, electricity may be collected from the grid and utilized to offset the cost of that energy.
The data is supplied to a monitoring platform, which generates a clear picture of PV output, cost savings, and plant performance.
Where is a Solar Meter Used Commonly?
A solar power meter is most often used for a range of applications in which total energy, efficiency, and location of solar systems must be determined, such as:
- Research into solar power
- Recognizing high-potential possibilities
- Laboratories in physics and optics
- Assessment of solar radiation
- Uses in agriculture
- Applications for meteorology
How Does A Solar Meter Operate?
Conventional electricity meters can only detect energy flowing in one direction. To put it another way, from the grid to the house. Solar meters, on the other hand, are bi-directional, meaning they can also track how much power the home exports to the grid.
Solar energy systems often produce the most electricity in the afternoon. When many individuals aren’t at home or the lights aren’t turned on. Home power usage, on the other hand, is generally greater in the mornings and nights.
Solar energy meters can assist to keep an account for these fluctuations in power output and consumption on a daily basis.
How is Surplus Power Generation Related to Solar Meter?
When the solar meter generates more power than is required, the excess is sent into the electric utility’s grid. When this happens, the meter begins to run backward.
This switch between the system and the grid guarantees that surplus power is used and no shortages occur. The surplus power produced by solar meters covers the times when there isn’t enough produced.
How Does A Solar Meter Make Solar Power Cost Effective?
The utility bill will get credits depending on the net number of kilowatt-hours returned to the grid when the solar power system produces more electricity than is utilized in a month.
If the solar power system generates less electricity than is consumed in a particular month, the shortfall must be made up by purchasing electricity from the utility.
Users would pay for the power they consume, minus any extra electricity generated by the solar panels.
What is Net Metering?
Solar energy system owners get credited for the electricity they provide to the grid through net metering.
For example, a PV system on a residential customer’s roof may create more power than the residence consumes during daytime hours. If the home is net-metered, the electricity meter will run backward to offer a credit against the amount of power used at night or during other times when the home’s electricity consumption exceeds the system’s output.
Customers are only charged for the energy they use “net.” Only 20-40% of a solar energy system’s output ever makes it into the grid, and this solar electricity is used to power neighboring customers’ loads.
You can create enough power to match your home’s electricity usage for the whole year with the right size solar energy system. However, the quantity of energy generated by your solar panels will fluctuate throughout the year: more in the summer months when the sun is higher in the sky and sets early, and less in the winter when the sun is lower in the sky and sets sooner.
Net metering compensates for these seasonal variations in solar production by crediting you for any extra power your panels generate and allowing you to utilize it at a later period.
How Does Net Metering Give You Control Over Electricity Bills?
Net metering allows utility users to produce their own power in an environmentally friendly and cost-effective manner.
Most solar customers create more electricity than they consume during the day, and net metering allows them to export that excess energy to the grid, lowering their future electric costs.
Without Net metering, the solar system might not prove to be as economical and cost-effective as one may presume.
How To Measure Solar Output?
The amount of solar radiation that reaches the absorbent surface represents energy production. Instruments can be used to measure the amount of solar radiation falling on the earth’s surface, and accurate measurements are required to provide background solar data for solar energy conversion applications.
To measure solar radiation, there are two types of meters.
What is a Pyrheliometer?
It’s used to measure the normal incidence of direct beam radiation. Pyheliometers come in a variety of shapes and sizes. Primary standard instruments such as the Abbot silver disc pyrheliometer and the Angstrom compensation pyrheliometer are the essential ones.
In the United States, the Eppley normal incidence pyrheliometer (NIP) is a standard instrument for practical measurements, whereas, in Europe, the Kipp and Zonen actinometer is commonly used.
The major standard procedures are used to calibrate both of these devices. The above-mentioned gadgets, by design, measure the sun’s beam radiation as well as a tiny portion of the sky surrounding it.
On a sunny day with clear skies, the contribution of the circumsolar sky to the beam is practically minimal, according to experiments utilizing different pyrheliometer types. A cloudy day, on the other hand, redistributes the radiation, making the circumsolar sky’s contribution to the measurement more relevant.
What is A Pyranometer?
It’s used to figure out how much total hemisphere radiation there is. A pyranometer detects diffuse radiation while it is shaded. Pyranometers provide the majority of solar data.
Pyranometers with thermocouple indications and photovoltaic detectors are available. The sensors should, ideally, be unaffected by the sun spectrum’s wavelength and angle of incidence.
Pyranometers are also used to determine the information to collectors by measuring sun radiation on sloped surfaces.
How Do You Read A Solar Meter?
On the display, there are both positive and negative numbers. The positive figure represents the amount of power imported from the grid, as measured by a traditional electricity meter without solar.
The negative figure represents the quantity of power taken to the grid from the solar system. This is the quantity of power created by solar, which is more than the home required at the moment.
In this example, the positive value is greater than the negative value, indicating that this property has exported more electricity than it has imported, resulting in power company reimbursements to the property owner.
What Are The Benefits Of Using A Solar Meter?
The solar meter’s most obvious benefit is to customers. People can minimize the amount of money they spend on electricity each year by installing a solar meter in their house.
If more energy is generated than consumed, consumers can even profit. The utility provider pays the retail rate for the surplus energy. Some other benefits of Solar meters include:
- The system is simple and cost-effective. It enables individuals to get fair compensation for the energy they generate without the need for a second metre or an expensive battery storage device.
- It enables individuals and companies to create electricity, relieving some of the strain on the grid, particularly during peak usage hours.
- Each residence has the potential to power two or three more dwellings. A neighbourhood may become self-sufficient if enough households in the area adopt renewable energy and solar meters.
- It encourages customers to participate actively in alternative energy generation, which helps to maintain the environment and conserve natural resources.
- Homes with solar meters are more conscious of their energy use and, as a result, more conscientious.
- Bushong, S. (2015). What are solar meters? Retrieved from https://www.solarpowerworldonline.com/2015/11/what-are-solar-meters/
- Naturally, S. (2018). How to read a Smart meter with solar power. Retrieved from https://www.solarnaturally.com.au/how-to-read-a-Smart-meter-with-solar-power/
- Rodvien, E. (2018). Smart meters: What every solar homeowner should know. Retrieved from https://www.solarunitedneighbors.org/news/Smart-meters-what-every-solar-homeowner-should-know/
- Sage, E. (2021). What is net metering? Retrieved from https://www.energysage.com/solar/solar-101/net-metering/
- SEIA. (2021). Net Metering Retrieved from https://www.seia.org/initiatives/net-metering
- Solar, J. (2021). What Are Solar Power Meters and How Do They Work? Retrieved from https://www.justsolar.com/blog/solar-power-meters
- Solar, S. (2013). A quick lesson in meter reading. Retrieved from https://solorasolar.com/a-quick-lesson-in-meter-reading/
What Problems Do Solar Panels Solve?
In environmental terms, solar panels can potentially solve a handful of problems, including;1. Air pollution2. Water pollution3. Greenhouse gases4. Reduction in fossil fuel use
For individuals, solar energy allows you to become completely self-sufficient when it comes to your electricity needs and can save you a lot of money in the long run.
What Are 3 Important Uses Of Solar Panels?
The three most important uses of solar panels are;1. Solar electricity. This can be used to power almost any appliance in your home, including TVs, computers, and fridges.2. Lighting. In addition to the use of low-power, LED lightbulbs, solar panels can provide an efficient, low-cost, and environmentally friendly way to provide lighting to homes. 3. Portable solar. In our modern, always-connected lives, our phones, tablets, and computers are almost always with us, and all run on batteries. Portable PV chargers can help keep our batteries topped up no matter where we are, as long as there is some sun to charge them.
Do solar panels give you free electricity?
Once the cost of the array is paid in full, the energy it produces is free. There are ongoing maintenance costs, too, such as annual panel cleaning, etc.
How much will my electric bill be with solar panels?
Suppose your solar array includes a solar battery backup system, and it is large enough to fully cover your energy usage per day. In that case, your monthly electric bill will be next to zero dollars, even with a grid-tied system.
If your solar array does not include a solar battery backup system, then at night, your house or business will use grid electricity. That cost will vary but expect to pay from 1/3-2/3 of your average electric bill, and that cost will fluctuate seasonally.
Do you save money with solar panels?
The simple answer is, Yes, you save money with solar panels. There is an initial upfront cost, but since solar panels are warrantied for 25 years, you will save money over time. You will also begin to see monthly savings in energy bills, but there are other ways that solar panels pay you back. Those include:1. Adding value to your home or commercial building 2. Monthly decreases in energy costs3. The ability to add more energy appliances without increased monthly costs4. The potential for tax credits for going solar
Can solar panels power a house 24-7?
Most definitely! Solar panels can certainly power a house 24-7, with the addition of a high-quality inverter and a suitable battery bank, of course. To power, a house under normal usage will require a massive solar array, though, and there will be a very expensive initial financial outlay.
Do I need to tell my energy supplier I have solar panels?
This depends on where you live, but in most cases, it’s not necessary to inform your energy supplier that you have solar panels. That said, you may be producing excess power with your solar system, in which case you may be able to sell that excess power back to energy companies.
In this case, you’ll naturally need to be in contact with them.
What Are Solar Cells Known as and Why?
Solar cells are also called photovoltaic (PV) cells. They are called so because the term ‘photovoltaic’ literally means light i.e. photo and electricity i.e. voltaic.
These cells generate electricity through the photovoltaic effect. This effect basically causes the generation of free electrons from the semiconducting silicon material of the solar panel when sunlight hits its surface.
What Type of Solar Panels Are Most Efficient and Why?
There are currently three types of solar panels available in the market that are:1. Monocrystalline2. Polycrystalline3. Thin-filmed
Among these, monocrystalline solar panels are known to be the most efficient among all others.
Does heat enter your home through the roof?
Absolutely. Heat enters your home through your roof, and on a hot day your attic can get up to 150 degrees Fahrenheit or more. Through conduction, heat from the sun warms your roof which then warms your attic and the rest of your home.
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What is Solar Net Metering: Working, Installation How To Apply
A solar metering energy system is a system that uses the electrical grid to store the excess electricity produced by domestic or commercial solar panels. The electrical meter installed inside a house or any other commercial building records the power consumption. Thus, people only need to pay for the net energy consumed by them.
To use this system, people need to have proper solar metering energy set up consisting of a solar panel, solar inverter, bidirectional meter, and an electricity connection.
Since there is an absence of a battery for power storage, an electricity connection is essential to transfer the unused energy to the grid. Therefore, this system is an economical option for people while limiting environmental pollution.
Functions of a Metering Energy System
A rooftop solar panel facilitates the generation of extra electricity than the requirement of people. However, due to the absence of a proper storage system, the electricity produced by solar panels gets wasted. The solar net metering system solves this problem by transferring the extra power to the electricity grid.
All the net metering solar power systems are connected to the electricity grid. When the solar metre produces an extra quantity of electricity, the bidirectional electric meter rotates in the reverse direction to measure the transfer of the electric unit to the grid.
The transferred electricity is credited to your bill. This means that when you need to use the electricity afterward, you only need to pay for the extra unit of electricity you consume. In addition, the bidirectional electric meter keeps a record of all the power exchanges. Therefore, you don’t need to maintain power utility on a daily basis.
Benefits of Metering Energy and Net Metering system
Net metering is an excellent way of promoting sustainable energy utilisation. It offers the following benefits to users and the environment:
- It prevents the requirement of storage battery: Solar panel owners don’t need to invest in batteries to store the extra power. The metering energy inverter easily transfers excess electric power to the grid. Whenever people need electricity, they can do so without paying an additional charge.
- It generates financial credit: Metering energy offers a great way of generating a passive income for people who have a large solar panel setup. This means that by generating multiple units of electricity, people can get either credit for further use or revenue from the state government or the electric department.
- It has a low maintenance cost: Net metering is a cost-effective option for using electric power. In addition, the transfer of excess power to the electric grid reduces the maintenance charge compared to a non-grid system.
Elaborated Process to Install Net Metering system in India
The procedure of net metering installation for metering energy in India differs in each state as different power distribution companies and electric departments have their own policies. However, the standard process involves the following steps:
- Applicants need to send an application to the SDO to seek permission to install a rooftop solar panel.
- Applicants need to collect the approval receipt from the sub-divisional officer.
- SDO completes the site verification within three days after application and approval.
- After the site inspection, SDO approves within 15 days from application submission.
- Consumer and SDO sign a net metering agreement within three days of filling up the net metering form.
- After installing the solar system, consumers shall submit a solar system certificate, property papers, installation certificate, and fees.
- In the end, a JE visits the site to inspect the solar panel installation. If all the rules are met, the JE gives permission to install a metering energy system.
Net Metering Approval Checklist
Applicants need to follow the given checklist to concisely monitor their solar metering energy application:
- Submit duly signed application.
- Provide roof right and occupancy proof.
- Applicant’s signature ID proof.
- Copy of recently paid electric bill.
- Applicants who are tenants or co-owner of property must submit the NOC of the owner or co-owners.
- Undertaking that is signed by a registered customer and attested by a notary public.
- Applicant’s photograph.
- Submit a registration form that is duly attested by the registered consumer.
- Subsidy sanction request letter.
- EPC agreement for CAPEX and PPA for RESCO.
- Receiving letter for metering energy application.
- Colored photo of the site with clear stamping of date and time before solar panel installation.
- Project report as per the Annexure-D format of tender document.
- Single lined diagram of the solar plant.
- System certification for the PV module inverters.
- Specifications of inverter and solar PV module.
- Non-judicial stamp paper agreement for metering energy connection.
Cost of Net Metering Installation
The cost of metering energy metre installation varies in different states of India. However, the general guidelines of DERC suggest that an applicant needs to pay the following charges to install net metering systems:
- Application charge: Rs. 500
- Registration charge: It varies according to the capacity of the solar panel.
The following table broadly demonstrates charges for each solar panel capacity for metering energy:
|1 to 10
|10 to 50
|50 to 100
|100 to 300
|300 to 500
The following table provides the information for meter charges paid by the customers:
|Type of net meter
|Charge (in Rs)
|HT net meter
|LTCT net meter
|Three-phase net meter
|Single-phase net meter
Metering Energy Stats and Policy in the Various States
India has achieved 40 gigawatts of rooftop solar energy generation by the financial year 2022. Earlier, the metering energy for rooftop solar panels was set at one megawatt, which was cut down to nearly 10 KW in 2020.
#1. Metering Energy stats in Punjab
Punjab stands at the tenth position for having the largest solar panel set up in India. In 2018 Punjab’s solar capacity was estimated at around 845 MW.
In the present scenario, the state gets more than 6% of its total electricity from solar net metering, which will rise in the coming future.
#2. Metering Energy stats in Haryana
The Haryana government provides financial assistance to applicants installing solar panels for net metering.
For the applicant’s convenience, the state government allows people to complete the registration process through online mode. The distribution licensee shall provide metering energy facilities to qualified consumers in its region of supply on a non-discriminatory and first-come, first-served basis.
#3. Metering Energy stats in Maharashtra
Maharashtra has the 8th largest solar panel set up in the country. In the 2018 financial year, Maharashtra’s fourth-quarter solar power generation from metering energy was around 1,311 MW.
The Maharashtra government uses a metering energy system to keep track of electricity generated in the state through solar panels.
#4. Metering Energy stats in Delhi
Delhi aims to produce 2,000 MW of power through metering energy until 2025. Although the government has mandated the installation of solar panels in all the government buildings, it still lags in achieving its target.
#5. Metering Energy stats in Karnataka
Karnataka state government has proposed to generate over 500 kW of power through metering energy. In addition, KERC has suggested a tariff rate of Rs. 3.82 per kWh for domestic solar installation, which has a capacity between 1 to 10 KW.
For larger solar panels set up of capacity 1 KW to 2 MW, the tariff rate is 2.84 per kWh.
A Net metering system is the best solar power generation system because it lets you use the required unit of electricity and exchange the excess power for revenue or credit.
People don’t need to set up and maintain an electricity storage unit because the bidirectional electric meter conveniently transfers unused energy to the electric grid.
over, this system promotes pollution-free power generation, which reduces harsh effects on the environment.
Can I use power from the net metering system during a power cut?
No, this system only allows you to use electricity when there is a power supply in your area. Since no battery or other storage device is involved, using electric current during a power cut becomes impossible.
Is it possible to sell surplus electricity generated domestically?
You can easily sell any surplus unit of electricity to the government or power distribution company by connecting your solar power generation system to the state’s electricity grid.
Can I use a general-purpose inverter for net metering?
No, rather it is crucial to use a solar inverter. The specific design of this inverter facilitates the convenient conversion of direct current obtained from solar panels into alternating current, which is then either used for household purposes or transferred to the grid.