How to Size a Solar Power System
Solar Panels are becoming more common place and investing in a solar photovoltaic system is a Smart solar solution for most homeowners. This now proven and reliable technology offers long-term performance with low maintenance. The latest solar panels and PV systems are cheaper, easier to install, maintain and operate more efficiently than ever before so its important to know how to size a solar power system in order to get the best from it.
The primary goal of any photovoltaic solar system is to offset all or some of your electricity needs with free power from the sun. The percentage of your energy needs that you will be able to supply with a solar system will depend on many factors, including your homes (or other location) power consumption, the efficiency of the system you install, and where your home is located. Ideally for solar panels this would be somewhere that experiences cold temperatures to keep the panels cool but that also receives plenty of sunlight to generate lots of free power.
Sizing a solar system can be tricky, especially if you are installing a system in a new home, RV, mountain cabin or do not know your homes energy needs. In such cases, how do you know how many solar panels or how much solar energy you require.
You could “guesstimate” your annual energy usage if you know your energy consumption patterns or have details of your energy bills. Having a reasonably accurate estimation of your energy consumption will help you design the correct size of the solar system you need.
For this simple example, let’s assume we want to design a solar photovoltaic system for an off-grid garden summer house (or shed) with battery back-up for the use of lighting at night. How would we size a solar power system for such an application.
How To Size A Solar Power System
Energy Consumption
What most people do first is to make a list of the power consumption of all the electrical appliances and devices that will be used in their particular home or location and an estimate of how long each appliance or device is switched-ON using energy each day.
Once this is complete multiply the power consumption (in watts) of each device by the number of hours it is on to give you the daily electrical consumption in watt-hours, as shown.
Then the total energy consumption is estimated at around 1440 watt-hours, or 1.44 kilowatt-hours per day. However, it is better to add a little extra on top, say 10% to 25%, to account for losses in the system, or the use of an extra electronic device not accounted for. Thus the new estimated value would be: 1440 watt-hours x 1.25 (25% extra) = 1800 watt-hours or 1.8 kWh.
Sun Hours Per Day
As solar power generation is based on incident sunlight on the PV panels rather than heat, it is necessary to know how many hours of direct sunlight the panel or panels will be exposed too throughout the day. The amount of energy you can get from solar electricity at an off-grid site depends on its location and the time of the year. Generally in the northern hemisphere you can expect to receive more sunlight between the months of April through to September and have a clear exposure to the sun for most of the day, e.g. 9am to 3pm.
A solar PV panel produces the most power when it is pointing directly to incident sunlight, so that the sun’s rays shine straight down onto its surface. Solar panel orientation is important as any solar panels should be located and angled to where they will receive as much sunlight as possible, averaged out during the course of the day, a month or a full year. Fortunately, most homes and gardens have good solar access with roofs that are often free from obstructions that can shade the solar panels.
The measurement for the strength of the sunlight striking the Earth at your location is defined as solar insolation and you’ll need to know the peak sun-hour figure for your location. Having a good solar site is important to ensure that the PV panels are exposed to bright sunlight every day of the year. It also ensures you are collecting the solar power more effectively as well. Generally during the winter season this can be as low as 4 hours or as high as 8 hours during the summer season.
Fortunately there are plenty of good websites available such as NASA’s Solar Insolation Website. Using this solar insolation database can help size the minimum solar electric (PV) system needed during the periods of the year with the shortest amount of sunshine for your particular site or location.
Lets assume then that for our particular location the lowest solar insolation occurs during the month of January with only 4.8 hours of sunshine per day. Therefore, the total peak power generated by the sunlight in the month of January will be: 1800 watt-hours/4.8 hours = 375 watts-peak, or 375Wp. This could be rounded off if required to 400Wp.
Determine Number of Solar Panels
We already have an accurate idea of the solar insolation for a particular site. We’ve done the electrical loads list survey so we know how much electric power we require on an average day. All that remains is to specify the type and number of photovoltaic (PV) panels that will produce the required power of 1.8 kilowatts.
There are literally hundreds of different solar panels to choose from and all vary in type, size, shape, and voltage rating. In most cases the size of a photovoltaic panel refers to the panel’s rated output wattage or electricity generating potential.
Solar panels can also have different voltage ratings depending upon their construction and size. Those that produce 12 to 48 volts output are generally used for off-grid applications. Maximum power ( Pmax ) delivered by a single panel at full sun is given as Maximum Power Voltage ( Vmp ) time Maximum Power Current ( Imp ).
For our particular off-grid example we required battery storage and back-up so the system will be powered using 12 Vdc photovoltaic solar modules for convenience.
How to Size a Solar Power System Summary
Hopefully by now you will have some idea of how to size a solar power system for your home or garden, whether off-grid with battery backup or grid-tied. These steps in determining the size of solar system are by no means the only ones, each case is different and there are different ways in sizing solar PV systems.
But the first step in going solar is not the size of the solar system, but reducing electricity usage through conservation and efficiency measures. Energy conservation and good home design plays an important role in keeping down the size and cost of a photovoltaic (PV) system. The use of energy efficient appliances and lighting, as well as non-electric alternatives wherever possible, can make an off-grid solar photovoltaic or even wind powered system a cost competitive alternative to the utility power grid.
The amount of sun-hours per day, days of autonomy and your homes average energy consumption will determine the size and ultimately the cost of any photovoltaic solar electricity system. Negative-watt-hours are the watt-hours you can save by conserving energy and not using it in the first place.
The cost of reducing your energy consumption with negative-watt-hours is about 20 to 30% cheaper than producing those same watt hours using an oversized PV system. Plus, the resulting smaller system means fewer solar panels, less space and less cost.
To learn more about solar energy, photovoltaic panels, or to learn how to build your own solar energy system using 100W panels to save money, Click Here to find more solar panels and start generating your own solar energy today.
What Factors Affect How Many Solar Panels You Need?
The size of your home and available roof space, the amount of direct sunlight your home receives, the type and efficiency rating of your solar panels, and how much energy your household use are all factors that affect how many solar panels you need. For example, if there are two identical homes powered by solar energy in California and New York, with exactly the same energy usage, the California home will need fewer solar panels because the state gets more sunshine. But two homes in the same neighborhood might not even need the same number of solar panels. It all comes down to the individualized needs of each household.
SunPower
SunPower designs and installs industry-leading residential solar and storage solutions across all 50 states. With a storied history of innovation dating back to 1985, no other company on this list can match SunPower’s experience and expertise.
SunPower earns its position as the top national installer on our list for a handful of reasons: It installs the most efficient solar technology on the residential market, offers the most expansive service area and backs its installations with a warranty well above the industry standard. All the while, SunPower pioneers sustainability efforts within the industry.
If that weren’t enough, SunPower systems come packaged with products all manufactured in-house by its sister company, Maxeon. This means that your panels, solar cells, inverters, battery and EV chargers are designed to work together and are all covered under the same warranty.
SunPower’s biggest downside? Its high-efficiency panels are considerably more expensive than most of its competitors’ products. However, its powerful panels are workhorses that make up for the initial cost with more backend production (think about this like spending more money for a car that gets more miles per gallon).
Blue Raven Solar
We like Blue Raven Solar because it understands that, for most homeowners, the cost of solar presents the biggest barrier to entry.
For that reason, Blue Raven Solar developed an innovative solar financing plan that offers in-house, flexible, zero-money-down options. The results speak for themselves, as Blue Raven Solar is now one of the fastest-growing solar companies in the nation and was recently acquired by SunPower. Its BluePower Plus plan (exclusive to Blue Raven) mimics the flexible structure of a lease while still providing the greatest benefits of owning your system.
Eligible homeowners enjoy 18 months of solar power before having to pay their first bill. When coupled with the federal solar investment tax credit (ITC), the initial energy savings can offset more than a third of the overall cost of a system before requiring a dollar down.
In contrast, other installers can only offer similar financing through solar leases, PPAs or third-party providers (such as Mosaic or Sunlight). Third-party loan providers can complicate the process, while opting for a loan or PPA will disqualify you from some of solar’s biggest benefits (additional property value, federal solar tax credit and local solar incentives).
How Can You Estimate the Number of Solar Panels You Need to Power Your Home?
So, based on these factors, how many solar panels power a home?
To roughly determine how many solar panels you need without a professional assessment, you’ll need to figure out two basic things: what is your energy use and how much energy your panels will produce. We dive into these in more detail below, but here are the general steps:
- Calculate how much energy your home uses
- Assess your roof space and the amount of sunlight your home receives
- Figure out the specific yield of solar panels in your area to estimate system size
- Check the wattage of the specific panels you intend to purchase
- Divide the wattage of your system by the solar panel wattage
Determine Your Home’s Electricity Needs
According to the latest data from the U.S. Energy Information Administration (EIA), the average American home uses 10,649 kWh of energy per year. However, this varies depending on the state. For example:
- Louisiana homes have the highest average consumption, at 14,787 kWh per year.
- Hawaii homes have the lowest average consumption, at 6,298 kWh per year.
To more closely estimate how much energy you use annually, add up the kWh reported on your last 12 monthly electric bills. These numbers will fluctuate based on factors like the size of your home, the number of residents, your electricity consumption habits and the energy efficiency rating of your home devices.
Electricity Needs for Common Household Appliances
The size of your home is a major indicator of how many solar panels you need, but you also have to take into account your daily energy use. For instance, a household with common appliances — such as a refrigerator, dishwasher, stove, etc — will consume less electricity than a home that has an added heated pool, central air conditioner, hot tub and electric vehicle.
These additional appliances and systems will dramatically increase your daily energy use, which means you will need more solar panels to offset your total energy consumption. As you plan your home solar system, make a list of all your appliances and systems so that all are accounted for in your final design.
assuming 350-watt solar panels are installed and average sun hours
Solar Panel Specific Yield
After you determine how many kWh of electricity your home uses annually, you’ll want to figure out how many kWh are produced by each of your solar panels during a year. This will depend on the specific type of solar panel, roof conditions and local peak hours of sunlight.
In the solar power industry, a common metric used to estimate system capacity is “specific yield” or “specific production.” This can be defined as the annual kWh of energy produced for each kilowatt of solar capacity installed. Specific yield has much to do with the amount of sunlight available in your location.
You can get a better idea of the specific yield that can be achieved in your location by checking reliable sources like the World Bank solar maps or the solar radiation database from the National Renewable Energy Laboratory. To estimate how many kW are needed to run a house, you can divide your annual kWh consumption by the specific yield per kilowatt of solar capacity.
For example, if your home’s energy needs are 15,000 kWh per year, and solar panels have a specific yield of 1,500 kWh/kWp in your location, you will need a system size of around 10 kilowatts. Paradise Energy Solutions has also come up with a general formula to roughly ballpark the solar power system size you need.
You can simply divide your annual kWh by 1,200 and you will get the kilowatts of solar capacity needed. So, if the energy consumption reported on your last 12 utility bills adds up to 24,000 kWh, you’ll need a 20 kW system (24,000 / 1,200 = 20).
You can also visit this resource to get an idea of how solar panels may perform at your house.
Watch below for more info on how your solar panels may be producing less electricity (watts) than what their power rating claims.
How Much Roof Space Does Your Solar Panel System Need?
On average, a solar system requires between 280 square feet and 350 square feet of roof space. Considering the average square footage of residential home roofs in the United States is 1,700 square feet, most people will not have any issues with solar panel installation.
But if you have a smaller roof, it’s best to invest in higher efficiency panels because you will need fewer panels to cover your energy costs. To help estimate the required square footage for your home solar, we’ve created a table that estimates how much space you’ll need for the most common solar system sizes:
based on the installation of 350-watt panels and average sun hours
The above estimates are based on the installation of 350-watt solar panels. If you decide to go with panels rated for more or less wattage, the required roof space will differ. For instance, you will need more roof space for panels with less wattage and less roof space for panels rated for a higher wattage.
It’s fairly simple to determine how much roof space you need, just multiply the number of solar panels you need by their size. The industry average square footage of a solar panel is 17.55 square feet, but this number will vary depending on your panels.
Below we’ve provided estimates for the amount of roof space you’ll need if you install a 9 kW solar system but choose panels with a wattage other than 350-watts:
- 300-watt panels: 30 solar panels = 530 square feet
- 325-watt panels: 28 solar panels = 500 square feet
- 375-watt panels: 24 solar panels = 425 square feet
- 400-watt panels: 23 solar panels = 400 square feet
Residential solar system size
In 2020, the International Energy Agency announced that solar energy has become the “cheapest electricity in history.” So it’s no wonder that solar energy is the fastest-growing electricity source in the United States! If you’ve been thinking about making the switch to solar, check out this comprehensive solar panel size chart from Solar Power Guide that sheds light on the average size of solar panels, how many cells solar panels have, and how much solar panels weigh: It should help you to integrate solar panels into your home or business with confidence!
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How Big Is a Solar Panel?
What is the most common solar panel size for homes? For a residential solar panel, size is fairly consistent across manufacturers: 65 inches (1.65 meters) by 39 inches (1 meter) is the average solar panel size that you find on the roofs of houses. That is about 5.4 feet long and 3.25 feet wide, which equates to around 15 square feet. This is typically regarded as the standard solar panel size How thick is a solar panel? That also varies depending on manufacturer; solar panel thickness typically ranges between 1.25 inches (32 millimeters) and 1.6 inches (40 millimeters). How much does a solar panel weigh? Most solar panels weigh around 40 pounds because they are constructed to be able to endure constant exposure to the elements. You may be wondering, “Can my roof support solar panels?” Chances are good that your roof will be able to support the weight of solar panels, but a reputable solar panel installer will ensure that your roof is safe for solar panels. They will also take the weight of the average snowfall in your area into account.
The average size of a commercial solar panel, such as those you would see on top of a hospital or in a field, is about 6.5 feet (2 meters) by 3.35 feet (1 meter), or 78 inches by 39 inches. They contain a system of at least 72 solar cells and can weigh around 50 pounds.
How Many Cells Does a Solar Panel Have?
First, let’s explore the size of a solar cell. A single photovoltaic cell is 6 inches by 6 inches. A solar panel is comprised of these photovoltaic cells arranged in configurations of 32, 36, 48, 60, 70, and 96 cells. How many cells are in a 300W solar panel? A 300W solar panel is the typical size for a residential solar panel, and these solar panels usually have 60 solar cells. Commercial solar panels or other large-scale projects most commonly have 72 or more solar cells.
Solar panel size does matter: The more solar cells a panel has, the more energy it can absorb from the sun. However, solar panels can vary in terms of efficiency, so the key factor when choosing solar panels should be their power rating. Most residential panels range between 250 and 400 watts per hour. As solar technology advances, the size of solar panels is decreasing as efficiency increases. It’s exciting to imagine just how bright the future of solar technology is!
Solar Panel Size Chart
If you have any questions about our solar panel size chart, please don’t hesitate to ask!
Size of Solar Panels
You’re here because you’ve heard the benefits of residential solar panels. Namely, lowered energy bills and decreased carbon footprints. You know the basics of how solar energy systems work – they convert sunlight into electricity for your home. Are you wondering how many solar panels will be enough to power your home? And if you have enough space to make it worth it? Read on and we’ll discuss everything you need to know about the size of solar panels, how many you’ll need, and what type of power production you can expect.
What Size Solar Energy System Do I Need?
First off, you’ll need to evaluate how much energy you typically consume in a given month. Knowing this will help you calculate how big of a residential solar energy system you’ll need to install. Keep in mind that your energy consumption will fluctuate given the time of year and where you live. You’re going to use up a lot more energy during hot summer months and during the dead of winter when your air conditioning unit and your heater are likely running non-stop, compared to in the fall and spring when the outside temperatures are more mild and don’t warrant as much electricity to run your heating and cooling units.
The average household in the United States consumes about 11,000kWh of electricity per year. And the average size of solar energy systems installed in most homes is 5kW. To break it down a little further, one kilowatt hour (kWh) is equal to 1000 watts of power used in one hour. You’ll need to gather data from your utility bills over the last year, and most utility companies will calculate your average automatically if you ask, to determine what your average monthly/yearly rate of energy consumption is. This will inform how many solar panels you’ll need to install in your home to equip your energy needs.
How Many Solar Panels Will I Need?
In general, if we’re going on the national average of 11,000 kWh of electricity used annually, and use 250 watt solar panels, we can estimate that the average home will need about 28 to 34 panels to generate enough solar energy to power the home.
How big are these solar panels? Physically speaking, the panels are about 65 inches by 39 inches for residential installations and they weigh about 40 pounds per panel. Solar panels used for commercial sites are a little bigger, but that’s because commercial buildings are usually larger and can contain the size of the panels. Residential panels are smaller in size and weight because they are mainly designed for a home roof, which would need to be able to bear the weight and size of the panels themselves.
Each panel will typically contain about 60 solar cells. These solar cells are what convert the sunlight into direct current electricity. The photons from the sun react with electrons released in the solar cells to generate electricity. Something called an inverter, which is part of your solar system, will then take this direct current electricity and convert it into alternating current electricity, the type of electricity needed to power your home appliances.
Most standard solar panels are between 230 and 275 watts. As stated above, based on the average amount of energy consumption per year and the standard solar panel wattage, this equates to about 28 to 34 physical solar panels that will need to be installed at your house. Just because this is how many panels you’d need to cover 100% of your energy consumption, this does not mean how many panels you’ll be able to physically install. To calculate this, you’ll need to know the size of your roof. If the most standard size solar panels are 17.5 square feet, and you have about 385 square feet of roof to install solar panels that will maximize the sunlight consumption, you can fit about 22 panels on your roof.
But, wait. This won’t cover 100% of the energy your home consumes. That’s okay. Nearly all residential home solar energy system owners are still connected to the grid. And it’s for this purpose. When you do not have enough energy converted from your solar panels to power your home, you can draw from the grid to power your home. In this way, you’ll only pay the utility company for the small amount of power you used from the grid, instead of needing 100% of it from the grid. The other great thing about solar systems is that if you produce more solar energy than you can consume in a given day, that excess is given back to the grid and the utility company will give you credit (read: money off your utility bill) for feeding your solar energy into the grid. Essentially, you can still come up with a
How Much Energy Will My Solar Panels Produce?
The key to answering this question is based on a number of factors, namely where you live and the time of the year. If you live in a state with high rates of sunshine (think California, Arizona) then you’ll be able to generate a lot more energy from your solar panels compared to someone living in Seattle.
In addition to this, the time of year will have a big impact on how much energy is produced. This is because when days are shorter in the winter, the amount of sunlight you have access to will be less than in the summer when the days are longer. Other factors that can affect the amount of energy your solar panels will produce are related to the positioning of your home. If you live in a really shaded lot, then your panels will not be able to produce as much power as someone who lives in the middle of a wide open field with no trees in sight. The key is figuring out what is the best positioning for your solar panels given your landscape, the slope of your roof, and the position of your house.
For an example, if you install 22 265-watt solar panels on your roof, you’ll generate about 5.83kW of electricity, leading to production of 6,366 kWh per year. What’s that mean dollar-wise? Based on average utility rates, expect your cost savings to be over 700 that year! Multiply that over the life of the system and you’ll understand why so many people are going solar! In an average of five short years, you’ll enjoy a 100% return on investment and at least 20 more years of pure savings.
energy bill if what you return to the grid is more than the amount you take from it.