How Many Solar Panels Do I Need? Calculation Guide

Most homeowners need 15 to 19 solar panels to meet their power needs. Understanding how many solar panels your home needs helps you evaluate solar quotes effectively so you can maximize your energy production and bill savings without sacrificing your budget. 

But how exactly do you calculate the right number of panels for your home? Solar expert Ben Zientara explains the process in the video below, or keep reading to learn how to estimate the number of solar panels you need step by step.

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Solar system sizing guide: how many solar panels are needed to run a house?

Home Size	Estimated monthly electric bill	Number of solar panels needed	Estimated roof space needed	Estimated solar cost after incentives
1,000 sq. feet	$77	8	141 sq. feet	$6,537
1,500 sq. feet	$115	12	211 sq.feet	$9,806
2,000 sq. feet	$153	15	264 sq.feet	$13,075
2,500 sq. feet	$191	19	334 sq. feet	$16,343
3,000 sq. feet	$230	23	405 sq. feet	$19,612

Estimates assumed 146 monthly peak sun hours, 400-watt solar panels, and a $0.17/kWh electric rate.

How many solar panels you need varies with multiple factors, like where you live, the design of your roof, and energy consumption. To find out how much solar your specific home needs, use this solar calculator, which considers your personal energy usage and local rates to give you a personalized estimate.

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Step-by-step guide: how to calculate how many solar panels you need

To estimate how many solar panels you need to run your house, ask yourself these three key questions:

1. How much solar power do I need?

2. How much sunlight does my roof get?

3. What solar panels will I use?

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1. How much solar power do I need?

To calculate how many solar panels you need, start by deciding how much solar power you want to generate.

Most homeowners aim to install enough solar panels to cover all of their electricity consumption. The average home uses about 900 kilowatt-hours of electricity each month. You can usually find your monthly electricity usage at the bottom of your electric bill. The table below outlines how many solar panels you need based on different energy usage levels: 

Monthly energy consumption	Number of solar panels needed*
800 kWh	14
1,000 kWh	17
1,200 kWh	21
1,400 kWh	24
1,600 kWh	27
1,800 kWh	31
2,000 kWh	34

Some people prefer to cover just a portion of their electricity costs, often due to budget restrictions, roof space constraints, or how their utility bills solar customers. There are also scenarios where you might install a larger solar system, like if you plan to get an electric car, install a pool, or electrify your appliances. 

No matter your situation, reviewing your energy bills and deciding how much of your electricity usage you want to cover with solar is the first step to estimating how many solar panels your home needs.

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2. How much sunlight does my roof get?

Solar panels use sunlight to generate electricity, so the more sun exposure your roof gets, the fewer solar panels you need to install. 

The amount of sunlight available depends on your home’s location and climate. For example, a solar panel produces significantly more energy in Arizona than in Alaska simply because Arizona gets more sunlight per day. 

Sunlight is measured by a metric called peak sun hours (PSH). The following map gives an estimate of how many peak sun hours each state gets per month:

Location	Daily Peak Sun Hours (PSH)	Monthly Peak Sun Hours	400-watt solar panel monthly energy production (kWh)
Alabama	4.5 – 5.4	150	60 kWh
Alaska	1.2 – 3	90	36 kWh
Arizona	7 – 8	222	88.8 kWh
Arkansas	4.5 – 5.4	132	52.8 kWh
California	5 – 7.5	192	76.8 kWh
Colorado	5 – 7	180	72 kWh
Connecticut	4.5 – 4.9	120	48 kWh
Delaware	4.5 – 4.9	135	54 kWh
Florida	5 – 5.9	162	64.8 kWh
Georgia	4.5 – 5.4	150	60 kWh
Hawaii	4 – 7.5	150	60 kWh
Idaho	4 – 6	150	60 kWh
Illinois	4.2 – 4.9	135	54 kWh
Indiana	4.0 – 4.4	120	48 kWh
Iowa	4.0 – 4.4	135	54 kWh
Kansas	5.0 – 6.4	165	66 kWh
Kentucky	4.0 – 4.9	135	54 kWh
Louisiana	4.5 – 5.4	150	60 kWh
Maine	4.0 – 4.4	120	48 kWh
Maryland	4.5 – 4.9	135	54 kWh
Massachusetts	4.5 – 4.9	135	54 kWh
Michigan	4.0 – 4.4	120	48 kWh
Minnesota	4.2 – 4.6	135	54 kWh
Mississippi	4.5 – 5.4	150	60 kWh
Missouri	4.5 – 5.4	135	54 kWh
Montana	4.5 – 5.4	135	54 kWh
Nebraska	5.0 – 5.9	150	60 kWh
Nevada	6 – 7.5	210	84 kWh
New Hampshire	4 – 4.5	120	48 kWh
New Jersey	4 – 4.5	135	54 kWh
New Mexico	6 – 7.5	210	84 kWh
New York	4 – 4.5	120	48 kWh
North Carolina	4.5 – 5.4	135	54 kWh
North Dakota	4.5 – 5.4	135	54 kWh
Ohio	4.0 – 4.4	120	48 kWh
Oklahoma	5.0 – 6.4	165	66 kWh
Oregon	3.5 – 6.4	150	60 kWh
Pennsylvania	4.0 – 4.9	120	48 kWh
Rhode Island	4.5 – 4.9	120	48 kWh
South Carolina	4.5 – 5.4	150	60 kWh
South Dakota	4.5 – 5.9	150	60 kWh
Tennessee	4.5 – 4.9	135	54 kWh
Texas	4.0 – 7.5	180	72 kWh
Utah	5.0 – 7.4	195	78 kWh
Vermont	4.0 – 4.4	120	48 kWh
Virginia	4.0 – 4.9	135	54 kWh
Washington	2.5 – 5	135	54 kWh
West Virginia	4.0 – 4.4	120	48 kWh
Wisconsin	4.0 – 4.9	135	54 kWh
Wyoming	4.5 – 6.4	165	66 kWh

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3.  What solar panels will I use?

The type of solar panel you use will dictate how many solar panels you need. Almost all home solar systems today use monocrystalline solar panels that have power output ratings between 400 and 430 watts. 

A solar panel’s wattage, sometimes called the solar panel size, indicates how much energy it produces. High-wattage panels generate more electricity, so you’ll need fear to meet your energy needs. 

The table below outlines how many solar panels you would need to cover an average household’s electricity usage based on different panel wattages:

Panel wattage	Panels needed for average electric usage
250 watts	26
300 watts	22
350 watts	19
400 watts	17
450 watts	15

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Factors that determine how many solar panels you need

Every home is unique, and so is every solar installation! Several factors influence the number of solar panels you need to install, including your electric bills, roof design, and the solar panels you choose.

Electric bills

The amount of electricity you use has the biggest impact on how many solar panels you need. If you use a lot of electricity, you’ll need a lot of solar panels!

Energy consumption can vary based on:

• The size of your family

• Your home’s energy efficiency

• The types of appliances you use

• The state you live in

For example, a home with an electric stove, water heater, and clothes dryer will have a higher electricity bill than one with gas appliances. Your home’s electric consumption will be listed in kilowatt-hours (kWh) at the bottom of your electricity bill.

Sunlight and shading

Solar panels rely on sunlight to generate electricity. Homes in sunnier places can install fewer solar panels to cover their electricity bills. For example, one 400-watt solar panel in Arizona can produce almost 90 kWh of electricity in one month. That same panel could only generate 36 kWh in Alaska. 

Shading can be an obstacle when installing solar panels. While trimming trees or bushes can help reduce shading, things like neighboring houses are harder to manage. If shading is unavoidable, you may need to install more panels on other parts of your roof to compensate for lost energy generation. 

Roof space and design 

Home solar panels are traditionally installed on rooftops, so the size, direction, and design of a roof have a tremendous impact on the number of solar panels you install. 

A typical 7.6 kW solar installation has an area of about 334 square feet, about 20% of the space of an average residential roof. If you have space constraints, consider high-efficiency panels that can produce more electricity in less space. 

South-facing roofs with an angle of 30 to 45 degrees are ideal for maximum solar energy production. Solar panels can still be installed if your roof faces another direction. But you might need a few extra panels to generate how much power you need. Complex roof designs with multiple dormers, vents, or skylights can limit how many solar panels you can install.

The following table outlines how much roof space is needed for different amounts of solar panels:

Number of panels	System size*	Minimum roof space required
10	4 kW	177 square feet
15	6 kW	265 square feet
20	8 kW	353 square feet
25	10 kW	442 square feet
30	12 kW	530 square feet

*Assumes 400 W panels

If your roof space is limited, don’t worry! You can still install a small solar system that offsets a portion of your energy usage and reduces your bills!

Home size

Although the square footage of your home isn’t the most accurate way to calculate how many solar panels you need, it can give you a general idea as you start your solar journey. The table below shows how many solar panels different-sized homes need on average:

Square footage	Number of 400 W solar panels needed
1,000	8
1,500	12
2,000	16
2,500	20
3,000	24

Utility rules and regulations

Every utility company bills solar customers differently, impacting the number of solar panels you should install. Some utilities don’t provide full credit for excess solar power produced beyond your monthly energy consumption, meaning you’ll want to install fewer panels to avoid overpaying for a larger system. 

There are also utility safety concerns to consider, which may restrict how many solar panels you can safely connect to grid infrastructure. One key safety guideline is the 120% rule recommended by the National Electric Code (NEC), which suggests that the combined amperage for your solar system and the grid connection should not exceed 120% of the safety rating of your electrical box. 

Local solar installers will design your system with these electrical safety and utility requirements in mind.

Personal budget and costs

Solar panels can deliver substantial electric bill savings, but they come with a significant price tag. Solar panels cost about $3.03 per watt installed, or about $14,000 after the federal solar tax credit is considered. That's not pocket change!

If the price is too high, you can install fewer solar panels you install to better fit your budget. There are also a few ways that make solar more affordable:

• Incentives and rebates: There are solar incentives and rebate programs that can lower the costs of going solar, including the 30% federal tax credit. Check your utility and local government websites for insights into the solar programs available near you. 

• Solar financing: Solar loans and solar leases typically require $0 down to go solar and can be paid for with monthly payments. The best way to pay for solar panels depends on your unique financial situation. 

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How many solar panels do I need to go off-grid?

Going completely off the grid with solar panels requires you to install enough solar to cover all of your energy usage, plus a big enough battery system to power your home after the sun goes down. Off-grid solar systems are not connected to the grid at all, so it’s even more important that your solar and battery systems are properly sized. 

For a monthly energy usage of 1,000 kWh, you would need at least 17 solar panels and three solar batteries to go off-grid. 

Monthly energy usage	Solar panels needed	Solar batteries needed	Total system cost after tax credit
500 kWh	9	2	$22,611
1,000 kWh	17	3	$34,373
1,500 kWh	26	5	$53,066
2,000 kWh	34	6	$66,718

Assumes 400-watt solar panels and 13.5 kWh lithium-ion batteries.

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Can solar panels run an entire house?

Yes, solar panels can power your entire house, but it might not be in the way you think.

For most home solar arrays, solar panels only run your house during the day, and any excess solar energy produced is sent to the utility grid in exchange for electric bill credits through a process called net metering. Those credits are then used to cover all or a portion of the costs of electricity you use from the grid when your solar panels don’t produce energy, like at night.

If you want to run your house entirely on solar power, install a solar battery that will store excess electricity generated during the day for you to use later, rather than sending it to the grid for bill credits. Battery storage is required for off-grid solar systems, as they don’t have the utility to fall back on. 

Usually, a solar installer will install enough solar panels to generate your daily electricity usage during daylight hours, so you have credits to offset your electricity costs later. Solar companies use advanced software to provide accurate quotes that include the exact number of solar panels to meet your energy needs.