How many solar panels do I need for my home?
The actual number of panels you’ll need to install depends on factors including your geographic location, panel efficiency, panel rated power, and your personal energy consumption habits. Importantly, the number of solar panels you need for your home directly impacts the price you pay for solar . While the answer isn’t always simple, we’ve put together some example cases to help you understand, at a high level, how many solar panels you need to install an effective home solar array.
We estimate that a typical home needs between 17 and 21 solar panels to cover 100 percent of its electricity usage. To determine how many solar panels you need, you’ll need to know: your annual electricity consumption, the wattage of the solar panels you’re considering, and the estimated production ratio of your solar system. You can calculate the number of solar panels you’ll need by dividing the system size by the production ratio, and again by the panel wattage.
What do you need to know to calculate how many solar panels you need?
Before you start to calculate the number of solar panels you need, there are several considerations to keep in mind:
- Your annual electricity usage
- The wattage of the solar panels you’re considering
- The estimated production ratio of your solar power system
How to calculate how many solar panels you need
You can calculate how many solar panels you need by dividing your yearly electricity usage by your area’s production ratio, and then dividing that number by the power output of your solar panels. Let’s break that down a bit:
Calculating how many solar panels you’ll need to meet all of your energy needs depends on several factors. The easiest way to find out how many panels you’ll need is to use our Solar Calculator. When you put in your address and estimated monthly power bill, we’ll do all of the math for you so that you can make an informed decision. If you’d like to do those calculations for yourself, we’ve explained our formula below to help.
The formula we used to estimate the number of solar panels you need to power your home depends on these key factors. Here are the assumptions we made, and how we did our math:
Annual electricity usage
Your annual electricity usage is the amount of energy you use in your home over a full year. Measured in kilowatt-hours (kWh), this number is influenced by the appliances in your home that use electricity and how often you use them. Refrigerators, air conditioning units, small kitchen appliances, lights, chargers, and more all use electricity.
According to the U.S. Energy Information Administration (EIA), the average American household uses 10,632 kWh of electricity per year (or 886 kWh per month), so we’ll use that number as the ideal solar panel system or solar array size, which would mean you could offset 100 percent of your electricity usage and utility bill with solar panels (in practice, it’s not this neat, but bear with us here). If you’re interested in getting a more exact number based on how much energy you use, check last year’s electric bills to find out your average electricity consumption. Once you have that number, feel free to plug it into the equations below.
Solar panel wattage
Also known as a solar panel’s power rating, panel wattage is the electricity output of a specific solar panel under ideal conditions. Wattage is measured in watts (W), and most solar panels fall in the range of 300 – 400+ W of power. We’ll use 390 watt panels in these calculations because 390-400 W is the most quoted capacity range on the EnergySage Marketplace according to our latest Intel Report.
Production ratios
A solar panel system’s production ratio is the ratio of its estimated energy output over time (in kWh) to its actual system size (in W). These numbers are almost never 1:1 – depending on how many hours of sunlight your system will get (which is primarily based on your geographic location), your production ratio will change accordingly.
For example, a 10 kW system that produces 14 kWh of electricity in a year has a production ratio of 1.4 (14/10 = 1.4) – this is an entirely realistic production ratio to see out in the real world. In the U.S., production ratios are usually between 1.3 and 1.6, so we’ll use those two numbers as the high and low estimates for our calculation.
Now, let’s work out the math
We have our three main assumptions (energy use, solar panel wattage, and production ratios) – so how do those numbers translate to an estimated number of solar panels for your home? The formula looks like this:
Number of panels = system size / production ratio / panel wattage
Plugging our numbers in from above, we get:
Number of panels = 10,632 kWh / 1.3 or 1.6 / 390 W
…which gives us between 17 and 21 panels in a solar array, depending on which production ratio we use (17 for a 1.6 ratio, and 21 for a 1.3 ratio). So, 17 panels at 390 W each result in a total system size of about 6.6 kW!
Solar panel cost
There is consideration for how many solar panels to buy without including cost as a factor. Solar panels cost $2.86/W on average. The total average cost of an installation is $20,020 for a 10 kW system (after accounting for the 30 percent federal solar tax credit). This varies widely depending on location, installation cost, and incentives with warmer climates being cheaper but needing more panels and vice versa for colder climates.
Main considerations to determine how much solar you need
Calculating how many solar panels you need can be done with the three inputs above, but digging deeper, there are many more factors at play in determining your ideal solar panel system size. Understanding production ratios, the relationship between system size and the number of panels, and the impact of home size can all be important when you’re designing your ideal solar panel setup.
How much solar power can your panels produce?
The amount of power (kWh) your solar energy system can produce depends on how much sunlight exposure your roof receives, which in turn creates your production ratio. The amount of sunlight you get in a year depends on both where you are in the country, and the time of year. For instance, California has more sunny days annually than New England. But in either location, you’ll be able to produce enough power to cover your energy needs and say goodbye to your utility bills – if you live in an area that gets less peak sunlight hours, you’ll just need to have a larger solar array system installed at your home. Thus, production ratios differ according to geographic location and a lower production ratio (because of less sunlight) means you’ll need more solar panels to get the amount of energy production you need.
Here’s an example: two comparably sized households in California and Massachusetts consume the average amount of electricity for an American household, which is 10,632 kWh annually as mentioned above. The California household needs about a 6.6 kW system to cover 100 percent of their electricity needs. By comparison, the comparable household in Massachusetts needs about an 8.2 kW system to cover their electricity needs. Solar panel systems in California are smaller than solar panel systems in Massachusetts but are able to produce the same amount of power because they’re exposed to more peak sunlight hours each year. Homeowners in less sunny areas, like Massachusetts, can make up for this disparity by simply using more efficient panels or increasing the size of their solar energy system, resulting in slightly more solar panels on their rooftop.
How many solar panels do you need for specific system sizes?
In our long example at the beginning of this piece, we determined that a 6.6 kW system would probably cover the average energy use for an American household if you live in an area with a production ratio of 1.6, which might be a realistic number for homes in most parts of California.
Let’s extend that a little further, and look at a few more examples. In the table below, we’ve compiled some solar panel number estimates for common solar system sizes seen on the EnergySage Marketplace. Again, the big caveat here is that we’re using 1.6 as the production ratio of choice. For California shoppers, this might actually be realistic, but for folks in the Northeast or areas with less sun, these estimates might be a bit high on the production end and low on the number of panels needed.
Number of solar panels needed for specific system sizes
System size Number of panels needed Estimated annual production 4 kW 11 6,400 kWh 6 kW 16 9,600 kWh 8 kW 21 12,800 kWh 10 kW 26 16,000 kWh 12 kW 31 19,200 kWh 14 kW 36 22,400 kWh
The table above again assumes that you’re using 390 solar panels and your production ratio is 1.6 – however, the number of panels you need to power your home and the amount of space that your system will take up on your roof will change if you’re using lower-efficiency panels or high-efficiency panels (which generally correlates to low and high power rating, respectively).
Perhaps one of the most difficult aspects of sizing a solar panel array is estimating the annual amount of energy usage for your household. A number of larger consumer products or add-ons can significantly change your annual kWh requirements and greatly impact how many panels you will need. For example, if you’re running central air conditioning or powering a heated swimming pool in your backyard, the size of your solar panel array could be drastically altered. To get a feel for the size you’ll need, you should evaluate the energy impact of various products you own or are considering for your home.
How much roof space do you have?
Ultimately, you’ll only be able to install as many panels as you can fit on your roof. Below is a table that will give you a sense of how many square feet your system will take up on your roof, depending on the power output of the solar panels you select.
Square footage of different size solar panel systems
System size 300 W panels (sq. feet) 340 W panels (sq. feet) 360 W panels (sq. feet) 400 W panels (sq. feet) 4 kW 234 207 195 176 6 kW 351 310 293 264 8 kW 468 413 390 351 10 kW 585 517 489 439 12 kW 702 620 585 527 14 kW 819 723 683 615
If your home is small or has an unusually shaped roof, the size of solar panels can be very important to consider. While those who have a large roof may be able to sacrifice some efficiency and buy larger panels to achieve the ideal energy output, homeowners with a smaller roof must be able to use fewer small high-efficiency panels – like those from SunPower, LG, or REC – to get optimal output. For those atypical roofs, you might end up getting a system design like this:
How does your home size affect the number of solar panels you need?
While solar panel dimensions have more or less remained steady over the past several years, the power output within the same area has dramatically increased. In fact, many manufacturers like SunPower have reduced the size of gaps between panels and use invisible framing and mounting hardware to keep the panels tight, efficient, and aesthetically pleasing. Check out the table below for a ballpark estimate of how many solar panels your home would need based on its square footage (assuming 390 W solar panels and a production ratio of 1.6).
Home square footage compared to the number of solar panels needed
Home size Estimated annual electricity needed Number of solar panels needed 1,000 sq. feet 4,710 kWh 8 2,000 sq. feet 9,420 kWh 15 2,500 sq. feet 11,775 kWh 19 3,000 sq. feet 14,130 kWh 23
How many solar panels do you need for common appliances?
By reviewing the various kWh requirements for everyday household appliances and products, one thing is clear: certain add-ons will dramatically change monthly energy use and can have an outsized impact on the size of the solar panel system you should install. For example, pairing your electric vehicle with solar panels is a great way to reduce carbon emissions and improve energy efficiency; however, it should be planned accordingly, considering it could potentially double the size of your solar energy system.
Though it’s certainly possible to install a solar system and then have a solar installer add more panels later to accommodate increased energy needs, the most pragmatic option is to size your system as accurately as possible based on your expected purchases – such as an electric vehicle, swimming pool or central air system. Asking yourself, “how many solar panels will I need for my refrigerator, my hot tub, etc.” is a great habit for any new solar homeowner.
Solar panel requirements for individual appliances
Product Average annual electricity needed Number of solar panels needed Refrigerator 600 kWh 1 Window air conditioning 215 kWh 1 Central air conditioning 1,000 kWh 2 Electric vehicle 3,000 kWh 5 Heated swimming pool 2,500 kWh 4 Hot tub (outdoor) 3,300 kWh 6
How many solar panels do I need for my home?
The actual number of panels you’ll need to install depends on factors including your geographic location, panel efficiency, panel rated power, and your personal energy consumption habits. Importantly, the number of solar panels you need for your home directly impacts the price you pay for solar . While the answer isn’t always simple, we’ve put together some example cases to help you understand, at a high level, how many solar panels you need to install an effective home solar array.
We estimate that a typical home needs between 17 and 21 solar panels to cover 100 percent of its electricity usage. To determine how many solar panels you need, you’ll need to know: your annual electricity consumption, the wattage of the solar panels you’re considering, and the estimated production ratio of your solar system. You can calculate the number of solar panels you’ll need by dividing the system size by the production ratio, and again by the panel wattage.
What do you need to know to calculate how many solar panels you need?
Before you start to calculate the number of solar panels you need, there are several considerations to keep in mind:
- Your annual electricity usage
- The wattage of the solar panels you’re considering
- The estimated production ratio of your solar power system
How to calculate how many solar panels you need
You can calculate how many solar panels you need by dividing your yearly electricity usage by your area’s production ratio, and then dividing that number by the power output of your solar panels. Let’s break that down a bit:
Calculating how many solar panels you’ll need to meet all of your energy needs depends on several factors. The easiest way to find out how many panels you’ll need is to use our Solar Calculator. When you put in your address and estimated monthly power bill, we’ll do all of the math for you so that you can make an informed decision. If you’d like to do those calculations for yourself, we’ve explained our formula below to help.
The formula we used to estimate the number of solar panels you need to power your home depends on these key factors. Here are the assumptions we made, and how we did our math:
Annual electricity usage
Your annual electricity usage is the amount of energy you use in your home over a full year. Measured in kilowatt-hours (kWh), this number is influenced by the appliances in your home that use electricity and how often you use them. Refrigerators, air conditioning units, small kitchen appliances, lights, chargers, and more all use electricity.
According to the U.S. Energy Information Administration (EIA), the average American household uses 10,632 kWh of electricity per year (or 886 kWh per month), so we’ll use that number as the ideal solar panel system or solar array size, which would mean you could offset 100 percent of your electricity usage and utility bill with solar panels (in practice, it’s not this neat, but bear with us here). If you’re interested in getting a more exact number based on how much energy you use, check last year’s electric bills to find out your average electricity consumption. Once you have that number, feel free to plug it into the equations below.
Solar panel wattage
Also known as a solar panel’s power rating, panel wattage is the electricity output of a specific solar panel under ideal conditions. Wattage is measured in watts (W), and most solar panels fall in the range of 300 – 400+ W of power. We’ll use 390 watt panels in these calculations because 390-400 W is the most quoted capacity range on the EnergySage Marketplace according to our latest Intel Report.
Production ratios
A solar panel system’s production ratio is the ratio of its estimated energy output over time (in kWh) to its actual system size (in W). These numbers are almost never 1:1 – depending on how many hours of sunlight your system will get (which is primarily based on your geographic location), your production ratio will change accordingly.
For example, a 10 kW system that produces 14 kWh of electricity in a year has a production ratio of 1.4 (14/10 = 1.4) – this is an entirely realistic production ratio to see out in the real world. In the U.S., production ratios are usually between 1.3 and 1.6, so we’ll use those two numbers as the high and low estimates for our calculation.
Now, let’s work out the math
We have our three main assumptions (energy use, solar panel wattage, and production ratios) – so how do those numbers translate to an estimated number of solar panels for your home? The formula looks like this:
Number of panels = system size / production ratio / panel wattage
Plugging our numbers in from above, we get:
Number of panels = 10,632 kWh / 1.3 or 1.6 / 390 W
…which gives us between 17 and 21 panels in a solar array, depending on which production ratio we use (17 for a 1.6 ratio, and 21 for a 1.3 ratio). So, 17 panels at 390 W each result in a total system size of about 6.6 kW!
Solar panel cost
There is consideration for how many solar panels to buy without including cost as a factor. Solar panels cost $2.86/W on average. The total average cost of an installation is $20,020 for a 10 kW system (after accounting for the 30 percent federal solar tax credit). This varies widely depending on location, installation cost, and incentives with warmer climates being cheaper but needing more panels and vice versa for colder climates.
Main considerations to determine how much solar you need
Calculating how many solar panels you need can be done with the three inputs above, but digging deeper, there are many more factors at play in determining your ideal solar panel system size. Understanding production ratios, the relationship between system size and the number of panels, and the impact of home size can all be important when you’re designing your ideal solar panel setup.
How much solar power can your panels produce?
The amount of power (kWh) your solar energy system can produce depends on how much sunlight exposure your roof receives, which in turn creates your production ratio. The amount of sunlight you get in a year depends on both where you are in the country, and the time of year. For instance, California has more sunny days annually than New England. But in either location, you’ll be able to produce enough power to cover your energy needs and say goodbye to your utility bills – if you live in an area that gets less peak sunlight hours, you’ll just need to have a larger solar array system installed at your home. Thus, production ratios differ according to geographic location and a lower production ratio (because of less sunlight) means you’ll need more solar panels to get the amount of energy production you need.
Here’s an example: two comparably sized households in California and Massachusetts consume the average amount of electricity for an American household, which is 10,632 kWh annually as mentioned above. The California household needs about a 6.6 kW system to cover 100 percent of their electricity needs. By comparison, the comparable household in Massachusetts needs about an 8.2 kW system to cover their electricity needs. Solar panel systems in California are smaller than solar panel systems in Massachusetts but are able to produce the same amount of power because they’re exposed to more peak sunlight hours each year. Homeowners in less sunny areas, like Massachusetts, can make up for this disparity by simply using more efficient panels or increasing the size of their solar energy system, resulting in slightly more solar panels on their rooftop.
How many solar panels do you need for specific system sizes?
In our long example at the beginning of this piece, we determined that a 6.6 kW system would probably cover the average energy use for an American household if you live in an area with a production ratio of 1.6, which might be a realistic number for homes in most parts of California.
Let’s extend that a little further, and look at a few more examples. In the table below, we’ve compiled some solar panel number estimates for common solar system sizes seen on the EnergySage Marketplace. Again, the big caveat here is that we’re using 1.6 as the production ratio of choice. For California shoppers, this might actually be realistic, but for folks in the Northeast or areas with less sun, these estimates might be a bit high on the production end and low on the number of panels needed.
Number of solar panels needed for specific system sizes
System size Number of panels needed Estimated annual production 4 kW 11 6,400 kWh 6 kW 16 9,600 kWh 8 kW 21 12,800 kWh 10 kW 26 16,000 kWh 12 kW 31 19,200 kWh 14 kW 36 22,400 kWh
The table above again assumes that you’re using 390 solar panels and your production ratio is 1.6 – however, the number of panels you need to power your home and the amount of space that your system will take up on your roof will change if you’re using lower-efficiency panels or high-efficiency panels (which generally correlates to low and high power rating, respectively).
Perhaps one of the most difficult aspects of sizing a solar panel array is estimating the annual amount of energy usage for your household. A number of larger consumer products or add-ons can significantly change your annual kWh requirements and greatly impact how many panels you will need. For example, if you’re running central air conditioning or powering a heated swimming pool in your backyard, the size of your solar panel array could be drastically altered. To get a feel for the size you’ll need, you should evaluate the energy impact of various products you own or are considering for your home.
How much roof space do you have?
Ultimately, you’ll only be able to install as many panels as you can fit on your roof. Below is a table that will give you a sense of how many square feet your system will take up on your roof, depending on the power output of the solar panels you select.
Square footage of different size solar panel systems
System size 300 W panels (sq. feet) 340 W panels (sq. feet) 360 W panels (sq. feet) 400 W panels (sq. feet) 4 kW 234 207 195 176 6 kW 351 310 293 264 8 kW 468 413 390 351 10 kW 585 517 489 439 12 kW 702 620 585 527 14 kW 819 723 683 615
If your home is small or has an unusually shaped roof, the size of solar panels can be very important to consider. While those who have a large roof may be able to sacrifice some efficiency and buy larger panels to achieve the ideal energy output, homeowners with a smaller roof must be able to use fewer small high-efficiency panels – like those from SunPower, LG, or REC – to get optimal output. For those atypical roofs, you might end up getting a system design like this:
How does your home size affect the number of solar panels you need?
While solar panel dimensions have more or less remained steady over the past several years, the power output within the same area has dramatically increased. In fact, many manufacturers like SunPower have reduced the size of gaps between panels and use invisible framing and mounting hardware to keep the panels tight, efficient, and aesthetically pleasing. Check out the table below for a ballpark estimate of how many solar panels your home would need based on its square footage (assuming 390 W solar panels and a production ratio of 1.6).
Home square footage compared to the number of solar panels needed
Home size Estimated annual electricity needed Number of solar panels needed 1,000 sq. feet 4,710 kWh 8 2,000 sq. feet 9,420 kWh 15 2,500 sq. feet 11,775 kWh 19 3,000 sq. feet 14,130 kWh 23
How many solar panels do you need for common appliances?
By reviewing the various kWh requirements for everyday household appliances and products, one thing is clear: certain add-ons will dramatically change monthly energy use and can have an outsized impact on the size of the solar panel system you should install. For example, pairing your electric vehicle with solar panels is a great way to reduce carbon emissions and improve energy efficiency; however, it should be planned accordingly, considering it could potentially double the size of your solar energy system.
Though it’s certainly possible to install a solar system and then have a solar installer add more panels later to accommodate increased energy needs, the most pragmatic option is to size your system as accurately as possible based on your expected purchases – such as an electric vehicle, swimming pool or central air system. Asking yourself, “how many solar panels will I need for my refrigerator, my hot tub, etc.” is a great habit for any new solar homeowner.
Solar panel requirements for individual appliances
Product Average annual electricity needed Number of solar panels needed Refrigerator 600 kWh 1 Window air conditioning 215 kWh 1 Central air conditioning 1,000 kWh 2 Electric vehicle 3,000 kWh 5 Heated swimming pool 2,500 kWh 4 Hot tub (outdoor) 3,300 kWh 6
How Many Solar Panels Do I Need?
Solar panels have enjoyed a meteoric rise in popularity in recent decades. That’s thanks in part to an increase in environmentally responsible behavior and the desire to reduce energy bills by exchanging traditional sources of heating, cooling and electricity with cleaner, more natural sources. If you’re thinking of making this switch, you’re probably wondering how many solar panels it takes to power a house.
While the answer can be a bit complicated, if you hire a professional or solar panel installation company to consult with, they’ll likely handle this part of the process as well (and may give you tips on how to maintain and clean solar panels).
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But if you’re wondering how many solar panels you may need, and you’d like to take a stab at calculating it yourself, you’ll need a few pieces of information: how much energy your household uses; how much space you have on your roof that can be used for solar panel placement, how many hours of sun your home gets and the wattage and relative efficiency of the photovoltaic (PV) solar panels you’ll be installing.
How to Determine Solar Panel Needs
In order to learn how many solar panels are needed to power a house, you’ll use a formula with three key factors, according to EnergySage: annual energy usage, panel wattage and production ratios. But what does that mean exactly?
Annual Electricity Usage
The first step is to determine your annual electricity usage; that’s the amount of electricity consumed by your entire household in a year. Measured in kilowatt-hours (kWh), this number includes all sources of electricity in your home, including small and large appliances, air conditioning units, lights, air purifiers and water heaters. The U.S. Energy Information Administration (EIA) indicates the average household consumes about 11,000 kWh of electricity per year.
Solar Panel Wattage
When choosing the best solar panels you may think they look mostly the same, but they aren’t exactly created equally, so you’ll need to know the wattage of the panels you’re hoping to install. The panel wattage is the amount of electricity emitted from the panel. Most solar panels range between 250 to 400 watts of power, so it’s safe to assume 300 is the average panel wattage you might find.
Production Ratios
According to EnergySage, a solar panel system’s production ratio is the ratio of the estimated energy output of a system over time (in kWh) to the actual system size (in W). You might think that this would be a 1:1 ratio – that you get out what goes in. But variations in the amount of sunlight that beams down on your home cause that not to be the case.
A 10 kW system that produces 16 kWh of electricity in a year will have a production ratio of 1.6 (16/10 = 1.6). In a place like Hawaii, which enjoys long days and consistent sunshine, it’s totally possible to have this type of ratio, whereas cloudy, rainy New England might see an average production ratio of only 1.2
Calculate How Many Solar Panels You Need
Here’s the actual formula, used by EnergySage, that you can use you’re hoping to determine how many solar panels you’ll need:
- Number of panels = system size / production ratio / panel wattage
- Using the numbers we’ve determined so far, we get:
- Number of panels = 11,000 kW / 1.6 / 300 W
That equates to about 20 to 25 solar panels to do the job. You can use this same formula to determine how many solar panels you’ll need to power your home. Or, you can use the easier route, which is to look at your energy bill to determine what you’ll need.
An Alternative Way to Figure Out Solar Energy Usage
If you’re not interested in doing the math on your own, simply look at your utility bills to figure out how much energy you’re using. Doing this allows you to multiply your energy usage by the number of hours of strong sunlight your home gets, then dividing that result by the wattage of the panels you’re thinking of installing.
Factors that Affect How Many Solar Panels You Will Need
Is there anything else to think about outside of the above calculations? Turns out, there are a few other things factors need to consider when determining how many solar panels to power a house.
Solar Panel Output Efficiency
Your solar panels won’t draw the sun’s energy at top capacity all the time. Think of those three-day bouts of rain that come in the fall, or large snowfalls in the winter that take several days to melt. Those are times you’ll need a buffer in your energy usage, so it’s recommended to have about 25% more solar panels than you need.
Hours of Sunlight
The amount of energy you’ll get from your solar panels is directly related to how much sun your home gets. More panels will be required if you live in an area without long hours of strong sunshine.
Wattage of Your Panels
Most solar panels range in wattage from 150 to 350 watts per panel. If you choose lower wattage panels, you’ll need more in order to generate enough energy for your home. Of course, that’s assuming you’d like to replace 100% of your energy usage with solar energy. If you’re only hoping for a partial conversion, the difference in solar panel wattage may not matter as much.
Cost of Solar Panels
How much do you want to or plan to spend on your solar panels? Before you buy, make sure you know how many make sense for your budget.
Solar Panel Size
To understand how many solar panels you’ll need, you must know the standard sizes of solar panels to know how many you can place on your roof. The area of a residential 60-cell solar panel is 17.62 square feet, and the area of a commercial 72-cell solar panel is 21.13 square feet. Solar panel installation companies will measure the area of your roof to determine how many panels can be installed safely.
