How Many Solar Panels Do I Need to Power My House?

Solar panels are up on millions of roofs across America. They’re up there because they can save homeowners money by lowering electric bills.

How did those homeowners know how many solar panels they needed? Well, almost all of them worked with a solar installer to design and install their systems. It’s usually best to get a quote from a reputable solar company.

That can be the most reliable way to know how many solar panels your home needs. If you want to explore on your own, here’s some helpful info.

Determining how many solar panels a house needs

A typical home needs 18-26 solar panels to cover 100% of its electricity usage. While there are many elements you can analyze to determine the ideal size of your future system, these four are most worth your time.

• Your household energy consumption
• Peak sun hours for your area
• Output of each solar panel
• Your solar goals

Here's a deeper look at each of these elements.

Energy consumption

When people begin thinking about home solar, the questions they ask are often similar:

• "How much energy does a solar panel produce?"
• “How many solar panels can I fit on my roof?"
• "How large of a solar system do I need?"
• "How many panels are needed to power a house?"

When determining the number of panels you need, it boils down to one factor: The amount of energy you use (or plan to use) in your home.

To figure out the right number of solar panels for your house, you should first determine how much electricity you use during an average month. Start with your last 12 monthly electric bills, add up your total usage in kilowatt-hours (kWhs) and divide by 12.

Both your 12-month total energy consumption and your 12-month average energy consumption are the baseline information you need about your energy consumption, because everything else depends on your electricity usage. The average American household used 863 kWhs in 2024, according to the US Energy Information Administration.

Peak sunlight hours

Solar panels rely on direct sunlight to generate electricity. Peak sun hours, a measure of the intensity and duration of sunlight a location receives, tells you how much sun they receive.

Where you live is a factor in how much energy your solar panels will produce in a day. For example, the American southwest regularly receives well over six peak sun hours a day, while the American northwest gets closer to four.

The best way to learn the amount of sustained sunlight your area receives is to speak with a solar energy system expert, like the ones at Palmetto. You can also consult the U.S. State Solar Resource Map from the National Renewable Energy Laboratory.

Credit: NREL

Solar panel output

Different solar panels have different electricity generation capabilities. Their output might vary depending on their efficiency or the number of solar cells they contain. Environmental factors like a panel's installation direction and shade from trees or a chimney may impact how much electricity your solar panels produce.

Electrical output also depends on the angle of installation. Solar panels for your home are installed in a solar array, which is just a group of solar panels installed together. The simplest array to install is a single rectangular shape. However, a single rectangular array requires a basic rectangular roof, so it’s incompatible with complex roof designs.

If your home features an unusually-shaped roof that doesn’t allow for a single array that meets your solar needs, the correct number of panels for your home will instead be arranged in multiple groups in different areas of your roof. Identical panels facing different directions at different angles will produce different amounts of electricity.

Your solar goals

People switch to solar for different reasons. Some want to save money on electricity bills, others want security through power outages, and others want to minimize their carbon footprint and use clean, renewable energy. Those are all good considerations to help you determine the number of panels to achieve your desired power output.

Let’s consider three common options.

• Depending on your utility’s net metering, net billing, and other policies, the number of solar panels that maximize your savings may vary. In some locations, it makes sense to install a system that will produce 100% or a bit more of your annual electricity consumption. In others it makes sense to install fewer.
• If avoiding power outages is your goal, a good solar battery storage system will ensure you store enough electricity to use when needed. You'll have a dependable and independent reserve of electricity.
• If you want to use solar to help the planet, you will need enough solar panels to produce 100% of your electricity needs so you don’t consume dirty electricity from the utility. 

Having a clear goal makes it easier for you and your solar installer to arrive at the right number of solar panels for your home.

How can I calculate the number of solar panels I need?

Palmetto has a solar savings calculator to help customers estimate the size of the solar energy system they need and their potential energy savings. 

Alternatively, you can use a formula to determine the system size you need to power your house:

(Monthly electricity usage / Monthly peak sun hours) x 1,000 / Solar panel wattage = Number of solar panels

Let's break this formula down in more detail.

Determine your energy consumption

Total the last 12 months of usage from your electricity bills and divide by 12 to get your home's monthly average. We’ll use 1,200 kWh per month as an example.

Determine how much sunlight you receive in your area

You need to know the peak sun hours your area receives. Keep in mind, average daily peak sun hours aren’t merely the hours when the sun is in the sky. They’re a measure of sunlight intensity over time. One peak sun hour is 1,000 watts of sunlight per square meter over one hour.

Peak sun hours directly impact the number of solar panels you need. If you live in a place that receives a lot of sunlight, such as Arizona, a smaller solar power array might fulfill all your needs. You would need a bigger system to achieve the same amount of energy production if you live in an area with less available sunlight, such as Massachusetts.

Let’s use Arizona, which receives an average of 7.42 peak sun hours per day.

Plug consumption and peak sun hours into the formula

1,200 kWh / (7.42 × 30) = 5.4 kW solar system

Note: We multiplied Arizona's average peak sun hours by 30 to get a ballpark estimate of peak sun hours the state gets per month.

Convert kW to total watts

Since 1 kW equals 1,000 watts, we will multiply 5.4 kW by 1,000:

5.4 × 1,000 = 5,400 watts

Determine the generation capacity of your potential solar panels

Different solar panel designs have different power generation capacities. 400 W panels are a common size installed by Palmetto

Divide the total watts above by the wattage output of a single solar panel to determine how many solar panels you will need:

5,400 / 400 = 13.5 solar panels needed to cover total electricity usage

Solar installers typically factor in many additional variables when sizing a solar power system; however, this number provides a baseline when thinking about your own solar power plans.

The number of solar panels you need depends on you

Besides the raw number of panels that will cover your electricity consumption, there are other factors that might affect the number of solar panels you can actually install.

How many solar panels do I need for my roof design?

The design of your roof determines how the solar panels will be installed, and how much sunlight they will get. If your roof is well-angled and features enough usable roof space, it can accommodate more panels. If there is only a small available area, you’ll be limited to a smaller number of panels.

The direction your roof faces also impacts the amount of sunlight your solar panels will receive. Better exposure (typically south-facing) requires fewer solar panels. 

How many solar panels do I need for home appliances?

Understanding how your appliances use electricity gives you insights into how you use electricity (and how you might save).

Credit: US EIA

To track the energy usage for individual appliances, you can install a home energy monitor or smart plug between the outlet and the appliance. Leave the usage monitor on for a week and use that data to calculate the total number of kilowatt-hours per day your appliances use.

Home appliances with the highest average electricity consumption include:

• Refrigerator
• Heater
• Air conditioner
• Dehumidifier
• Dishwasher
• Electric oven
• Washing machine
• Dryer
• PCs (especially gaming computers)

Once you know the energy consumption of your appliances and when they’re used, you can figure out the size of the solar panel system you need to install to generate sufficient electricity for your energy usage.

How many solar panels do I need if I have a lot of trees?

Like anything that blocks the sun from your panels, the beautiful trees around your home can impact how much solar energy your solar panels generate. 

You may have to trim trees so your solar panels can generate as much electricity as you need, which can be a more cost-effective solution than adding more solar panels. If you don’t trim them, your roof might be shaded during certain times of the day and that would require a larger system to compensate for the decreased production.

How many solar panels do I need for my future energy plans?

Is your electricity consumption likely to increase in the coming years? When assessing your solar panel requirements, think about any big changes in your electricity usage that might develop. This includes purchasing an electric vehicle, a larger HVAC system, leveraging net metering, and anything else that affects the size of your electricity bill.

Once you have your system size estimate, the best way forward is to get a free quote and savings estimate with Palmetto. Use our solar savings calculator to estimate how much you could save.

Frequently asked questions

How many solar panels do I need to power my home?

This answer starts with knowing your current and projected electricity usage. We work with you to build a system with the generation capacity to meet your needs. Energy usage, budget, utility policies, incentives, and property all go into the overall design of your system.

How many solar panels can I put on my roof?

You can put as many solar panels on your roof as will fit. This isn’t necessarily the best or most energy-efficient answer. You want your system to be a match to your energy usage and needs. This means having the right size, knowing local net metering or incentive policies, optimizing specifics such as the direction and angle of the panels, and meeting your budget and your family’s needs. 

What happens if solar panels make more electricity than I need?

If you have battery storage as part of your solar system, extra electricity will be stored in your batteries. If you don’t have battery storage or your battery is full, extra electricity typically goes to the grid. If you are sending, or using, power to and from the grid, you need to know about plans such as net billing or net metering in your state or area.

Disclaimer: This content is for educational purposes only. Palmetto does not provide tax, legal, or accounting advice. Please consult your own tax, legal, and accounting advisors.