How much electricity does a solar panel produce? A summary of key facts for solar
Electricity produced from solar panels is an essential part of decarbonisation of our electricity and energy system. In contrast to traditional electricity supply, where electricity is produced centrally and households merely consume, they can now become producers of energy by installing solar panels. With this, households can gain autarky, protect against high electricity prices, and help decarbonize our electricity system.
Of course, solar can also be installed at utility-scale in large solar farms, which results in increased (cost) efficiency compared to rooftop installations. Either way, solar will be a crucial part of the future energy system, which provides low-carbon electricity at low cost and free from fuel-supply dependencies. And the current energy crisis in Europe and Russia’s attack on Ukraine have even further accelerated demand in residential solar energy.
In this post we summarize a few key terms and numbers about solar power installations which should make it easy for newcomers to understand such systems, but also provide a good “cheat sheet” for folks with some experience.
What is kilowatt-peak (kWp)?
Kilowatt-peak refers to the maximum power a solar system can deliver under best conditions. (At full exposure to sunlight at the best angle and at cold temperature). The unit kWp is typically used to describe the size (or capacity) of the solar installation. It is defined by the area covered with panels and the type of panels used. Note: often kWp is just simplified to kW, meaning kWp and kW are used interchangeably in the context of solar installations. (You may hear “I have a 5kW solar system installed on my roof.”)
Typical solar panels used today produce 400-650W (0.4-0.65kW) at ideal sun exposure and temperature.
What are the dimensions of a solar panel?
Historically typical panel sizes were 1.0×2.0m or 1.6×2.0m. Nowadays the panel sizes can vary from 1.6×2.0m to 1.2×2.3m. The panels are composed of solar cells, with larger panels having more cells (typically panels have 60, 72 or 144 cells). It depends on the roof size and shape, which panels are optimal to use.
The amount of electricity (energy) produced per installed capacity is defined by its size and the duration it is receiving sunlight. Consider a 3kW (or 3 kWp) system exposed to full sunlight at perfect angle for 2 hours at noon: this will produce approximately 3kW 2h = 6 kWh of energy in those two hours. In the morning and evening the light is less direct and production is lower, and obviously at night there is no production at all.
Solar panels produce most when it is cold and sunny, each extra degree means less production. The production also depends on the hours of sunlight per day, and seasonal patterns. There are tools available for estimating the potential for solar electricity production for any location on earth.
If you want to have just a few simple guidelines, you can go with the following for the yearly energy production per installed kWp:
- 1600 kWh in Southern Europe (Madrid, Spain)
- 1100 kWh in Central Europe (Munich, Germany)
- 900 kWh in Northern Europe (Tallinn, Estonia)
- 1700 kWh in Los Angeles, USA
- 1600 kWh in Texas, USA
- 1300 kWh in Boston, USA
- 1000 kWh in Vancouver, CA
As you can see the difference between Central and Northern Europe for yearly production is not as big as one might assume. But of course the further South you move, not only does production increase, it also becomes more evenly distributed over the year.
In summary, a very simple ballpark number for Central Europe is: annual production of 1000kWh per installed kW.
How much energy does a square meter of solar panels produce?
For our reference cities, a 1 square meter panel area could produce from 200 to 364 kWh electricity annually. (That’s about 10% of the annual general electricity need of a European household.)
A typical household in Europe uses approximately 3000-4000 kWh of general electricity per year. This means (based on the production numbers from the previous question) a system between 1.5kWp and 4.5kWp would be required to cover the household’s yearly electricity need, depending on location and yearly consumption. (Or in square meters: 8-20m 2 of solar panels).
How Is Solar Panel Power Production Measured?
The output measured under laboratory conditions determines the rated wattage of a solar panel. This testing also dictates the solar panel efficiency rating. For example, if a PV module generates 220 W per square meter, it is 22% efficient.
As of June 2023, SunPower and Canadian Solar produce the most efficient solar panels in the industry — both companies have reached 22.8% efficiency. However, many other brands make solar panels with an efficiency of over 20%.
Solar panels are manufactured in standard sizes, and wattage increases with size. Smaller, 60-cell panels are common in residential installations, while 72-cell panels are normally used in commercial and industrial installations. You can find other sizes, but 60-cell and 72-cell panels are the most common.
Factors Affecting Solar Panel Power Capacity
The nameplate wattage of solar panels is determined under ideal conditions that do not reflect real-world applications. For example, a 360 W panel may operate closer to 300 W when installed on a rooftop with average sunlight conditions. Below are some of the factors that affect the energy production of a solar panel.
Amount of Sunlight Exposure
Solar panels generate more electricity when they get more hours of direct sunlight. Assuming you compare PV systems of the same size, you can expect higher productivity in sunny states like California. You can use the World Bank Global Solar Atlas for an idea of the sun hours available in your location.
Ambient Temperature
Increased sunshine makes solar panel systems more productive, but high ambient (air) temperatures can have a detrimental effect. High heat can temporarily reduce the ability of PV cells to convert sunlight into electricity.
Solar panels have a temperature coefficient, which describes how much power their cells lose per Celsius degree as the panel heats up. Most solar panels have a temperature coefficient of around.0.3% to.0.5% per °C. This means a temperature rise of 10°C will cause a power loss of around 3% to 5%.
Solar Battery and Inverter Efficiency
A solar panel system includes other components, such as inverters and batteries. The inverter is necessary since it converts the DC power (direct current) generated by solar panels into the AC power (alternating current) used by home appliances. Battery storage is optional in grid-tied solar systems, but necessary for off-grid systems.
These devices waste some of the power your system generates since they are not 100% efficient, but you can find inverters and battery systems with an efficiency of over 95%. Although this represents a small loss, it is worth considering when designing a solar energy system.
Estimating the Potential Power Output of Solar Panels
The amount of power a solar array can generate depends on sunshine and weather conditions. To determine a system’s exact power output at any given time, you must measure it directly. But you can use the Global Solar Atlas to estimate how much energy your system will generate annually:
- Using the Global Solar Atlas, click on your location and look for a value called specific photovoltaic power output or PVOUT.
- This value estimates the annual productivity of solar panels in your location, measured in kilowatt-hours generated per kilowatt of peak capacity (kWh/kWp).
- For example, if the Atlas shows a PVOUT value of 1,500 kWh/kWp and you have an 8 kW system, you can expect to generate 12,000 kWh of electricity per year.
- Say you have an electricity tariff of 16 cents per kWh, you could save 450,920 in annual electricity bills.
- To determine the energy production of each panel, divide the total output by the number of panels. For example, if you have an 8 kW system with 20 panels that generate 12,000 kW total, each panel should generate 600 kWh of energy per year.
Power Output by Solar Panel Type
The main factor that determines panel power output is the type of solar cell: monocrystalline (most efficient), polycrystalline (intermediate) or thin-film (least efficient). The following table compares the typical power output you can expect when comparing types of solar panels.
Power estimates reflect typical wattages for residential solar panels with a size of 65 inches by 40 inches (or similar), which is common in home installations. Power output ratings will increase or decrease with solar panel size.
As you can see, high-efficiency monocrystalline panels can generate more watts of power compared to thin-film and polycrystalline panels. Homeowners with limited space can use monocrystalline panels to achieve the highest possible electricity output.
Maximizing Solar Panel Power Generation
Solar panels have a rated wattage and efficiency, but their actual performance depends on many external factors. You can achieve higher efficiency by following these recommendations:
- Install your solar panels in an unshaded area.
- Clean your solar panels regularly to prevent dust and dirt from accumulating and blocking sunlight.
- Monitor the daily electricity output of your solar panel system. Many inverters have a built-in monitoring app you can install on your smartphone. Contact your solar installer if you notice any dips in system performance.
We recommend a professional installation if you plan to go solar. Solar panels that are not wired properly can suffer from low productivity or even permanent damage. Incorrectly installing your system can also void your manufacturer’s warranty. The best solar companies ensure proper solar panel installation and help you troubleshoot any issues over time.
Factors That Affect Solar Panel Output
The electricity output of photovoltaic modules depends on the direct sunlight reaching their surface. That’s why solar panel productivity is higher in sunny locations and lower in cloudy weather conditions or in places where excessive shade comes from surrounding buildings. Under identical sunlight and temperature conditions, the energy output of solar panels depends on their efficiency.
Let’s discuss the primary factors that determine the amount of electricity generated by solar panels.
Efficiency
Solar panel efficiency can range from less than 10% to more than 20%. The efficiency rating is simply the amount of sunlight that gets converted into electricity, when the panel is tested under ideal conditions in a laboratory. As of 2023, the most efficient solar panels available in the market range from 20.60% to 22.80%, with SunPower panels at the top of the efficiency ranking.
In actual installations, the efficiency of solar panels is affected by factors like dust accumulation and high temperatures. You can prevent dust buildup by having your solar panels cleaned one or two times a year. There’s nothing you can do about high temperatures, and panels lose from 0.30% to 0.40% of their productivity for every Celsius degree of temperature rise. Fortunately, this is a temporary effect, and the lost efficiency gets recovered when panels cool.
Type of Panel
There are three main types of solar panels: monocrystalline, polycrystalline and thin-film. Here’s what you need to know about them.
- Monocrystalline panels are the most efficient.Each of their photovoltaic cells is a single crystal of high-purity silicon, which has a sophisticated production process.
- Polycrystalline panels have intermediate efficiency ratings. Their solar cells are made of multiple silicon crystals, as opposed to a single piece. This has a negative effect on panel efficiency, but production costs are less.
- Thin-film panels are the least efficient. This type of solar panel uses a layer of photovoltaic material, without crystalline structure, applied on a rigid or flexible substrate. However, there are now thin-film panels of the same efficiency as polycrystalline cells.
Thanks to their high efficiency, monocrystalline panels have the highest kilowatt-hour output per square foot covered. Industry experts consider them the best solar panels for homes, especially if roof space is limited.
You can classify solar panels based on the number of their photovoltaic cells. Most panels have either a 60-cell design in a 6×10 arrangement or a 72-cell design in a 6×12 layout.
- Traditionally, 60-cell panels are more common in home solar panel installations, while the larger 72-cell panels are used in commercial and industrial roofs.
- A 72-cell panel will be 20% more productive than a 60-cell panel because it has 12 more cells. Solar panels with a capacity of more than 400W normally have a 72-cell design.
Some solar manufacturers offer an in-between size and design with 66 cells. Some solar brands use half-cells with a higher efficiency, but the overall solar panel size does not change. They have 120, 132 or 144 half-cells in the same space (instead of 60, 66 or 72 full-sized cells).
Position
To increase the energy produced by solar panels, make sure they face the sun for as much time as possible throughout the year. The sun’s position in the sky constantly changes, and the ideal tilt angle for solar panels depends on your geographic location. The sun is lower in the sky as you reside farther north, and this means solar panels must be tilted more to increase the hours of direct sunlight.
Other than the optimal tilt angle, you must also consider the orientation of solar panels. In northern hemisphere countries like the U.S., it makes sense to have your panels face south because there is more sunlight coming from that half of the sky. However, west-facing and east-facing panels are useful in some applications:
- East-facing panels have a higher power production during the morning because the sun rises in that direction. They work well in schools and other buildings with a high energy consumption during the morning.
- West-facing panels are more productive in the afternoon. They make sense for buildings with a low morning consumption and a high afternoon consumption.
Location
As you can see in the Global Solar Atlas, annual sunshine depends on your geographic location. If two 6-kW solar power systems are installed in different states and one of them gets 30% more sunshine during the year, energy production also increases by around 30%.
How Many Solar Panels Do I Need?
The number of solar panels a home needs depends on three things: sunshine, home electricity consumption and the panel wattage used. For an accurate calculation and a professional design, you should contact one of the top-rated solar installation companies.
You can estimate the number of solar panels needed using the following information:
- Your annual electricity consumption in kWh.
- The specific photovoltaic power output in your location, which you can get from the Global Solar Atlas.
- The panel wattage you plan to use. You can assume 350W for residential solar panels if you don’t have a specific panel brand in mind.
U.S. homes consume an average of 10,632 kWh/year, according to the Energy Information Administration. You can search for your location in the Global Solar Atlas and click to display the PVOUT value. For example, if you get 1,400 kWh/kWp, you can divide both values to get an estimated capacity of 7.6 kW (or 7,600 W).
- At this point, you only need to divide the total system wattage (7,600 W) by the individual solar panel wattage (350 W).
- In this case, the homeowner would need 22 panels, reaching a total capacity of 7,700 W.
As of 2023, the average cost of solar panels in the U.S. is 5000.85/watt. You can expect to pay around 21,945 for a 7.7-kW system. However, you get a 30% federal solar tax credit. thanks to the Inflation Reduction Act. The tax credit in this case is 6,583.50, and the net cost of your system drops to 15,361.50.
What To Do With Excess Energy
Solar panels don’t produce electricity evenly throughout the day. Their output gradually increases during the morning, reaching a peak around noon before decreasing in the afternoon. Because many homes are empty during the day, solar panels often generate excess energy that doesn’t get consumed right away. Homeowners have two options to deal with this excess electricity, and each have their pros and cons:
- Storing surplus electricity in a battery system and using it later
- Exporting excess energy to the local grid and getting a credit on your next electric bill
A battery system gives you the option of storing solar electricity to be used at any time, even at night when panels are no longer productive. Solar batteries also qualify for the 30% federal tax credit, and additional incentives may be available from your local government or utility company. If you purchase a solar battery capable of operating off-grid, you can use it as a backup power system during blackouts. However, home battery systems are expensive, and they can add more than 10,000 to your solar installation costs.
Exporting surplus solar power to the grid is a convenient option because you can trade unused electricity for power bill credits. However, the kWh price you sell your electricity for is normally lower than the retail price you pay, which means you don’t save the full value of each kWh. States have different buy-back rates, so your location matters. And many states don’t even have a net metering or solar buyback policy, which means you don’t get credit for sending excess energy to the grid. Battery storage becomes your only option in this case.
Frequently Asked Questions About Solar Panel Output
How much power does a 500-watt solar panel produce per day?
Assuming favorable sunlight conditions, a 500-watt panel will produce around 2 kWh per day, and more than 700 kWh per year.
How many solar panels are needed for a 2,000-watt system?
This will depend on the individual wattage of the solar panels you choose. Simply divide the total capacity required by the panel wattage:
What does the average solar panel produce per day?
Residential solar panels have typical power ratings of around 350-400 W. Under favorable sunlight conditions, a panel of this wattage can generate over 1.5 kWh of electricity per day.
What will a 2,000 watt solar system run?
According to the Energy Information Administration, U.S. homes consume 10,632 kWh/year, on average. With decent sunshine, a 2,000-watt solar energy system generates more than 2,800 kWh/year, covering 26% of the electricity usage of a typical home; 2,800 kWh/year is roughly equivalent to the annual consumption of a three-ton central air conditioner.
Leonardo David is an electromechanical engineer, MBA, energy consultant and technical writer. His energy-efficiency and solar consulting experience covers sectors including banking, textile manufacturing, plastics processing, pharmaceutics, education, food processing, real estate and retail. He has also been writing articles about energy and engineering topics since 2015.
Understanding System Losses
Generally 14% is used to account for system losses, but this number can vary.
For example, when you use the PV Watts calculator online, they automatically account for 14% efficiency losses.
The below table outlines what those losses entail:
So, as you can see efficiency losses could result in an under performing panel, and thus a lower power output.
Final thoughts
As you can see, average solar panel output per day is affected by a range of factors and it is impossible to give an accurate estimate without taking these factors into consideration.
If you would like to learn the power output of your proposed solar array, we recommend using the NREL PV Watts solar calculator.
This calculator takes into consideration all the above mentioned factors giving you one of the most accurate results on the Internet.
Visiting the BGE(Baltimore Gas and Electric) Outage Center
To check the BGE power outage status, you can visit the BGE Outage Center. BGE is short for Baltimore Gas and Electric, and it is a utility company.