How many solar panels do I need for my house?

How many panels do I need?

The first step in figuring out how many solar panels you need to fully power your home with solar is determining your energy usage.

According to the U.S. Energy Information Administration (EIA), the average home in the U.S. used 10,715 kilowatt-hours (kWh) of electricity in 2020. That comes to an average of about 893 kWh per month. However, usage rates vary. In 2020, the average residential customer in Hawaii used only 6,446 kWh, while the average resident of Louisiana used 14,407 kWh.

Energy usage by region

The size of your home also impacts the amount of energy you consume. Larger homes typically have more people, take more energy to heat and cool and contain more appliances, so they consume more electricity overall. This means they'll need more solar panels.

We spoke with Matthew Culley, senior consultant at Renu Energy Solutions (a solar installer in the Southeast), to get an estimate of how many solar panels different sizes of homes might need.

Solar panels needed by square footage

If you’re in another part of the country or your home doesn’t get much sun for whatever reason, these estimates might not be correct for you. You can try to calculate a better estimate based on your energy consumption and the efficiency of your planned solar panels, but the reality is that it’s often easier and more accurate to consult a professional.

So how do you gauge your average energy consumption?

When you ask a solar panel installer for an estimate, they may ask for your utility bills so they can see how much energy your home uses each month and the total for a year. Looking back on at least one year of energy consumption is an excellent way to determine your long-term needs; energy consumption varies from one month to the next and from season to season. If you've lived in your home for less than a year, you might need to wait a few months to accumulate enough data.

Your solar panel installer may also take satellite images of your house to see your roof at different times. This is a good way to tell which parts of your roof are most exposed to the sun throughout the day. This information will help your installer create a proposal for the appropriate number of solar panels.

How much energy does a solar panel produce?

Most solar panels produce between 250 and 400 watts of power. Since the amount of energy a solar panel produces varies from one type of panel to the next, ask how much a given solar panel produces when you seek a quote for solar panel installation on your home.

Your results will likely also vary from what’s advertised. Not all areas get the same amount of sunlight, and different parts of your roof will have different sun exposure levels.

» MORE: Solar panel efficiency

What affects solar panel output?

Several factors impact solar panel output, including the panel’s size and the type of panel in question. Larger panels have the capacity to capture more sunlight and generate more electricity, and different solar technologies have different efficiency ranges. Most solar panels can be divided into the following categories:

• Monocrystalline: These highly efficient solar panels are made with pure silicon. In addition to being very efficient, they also have a longer service life than most other types of panels.
• Polycrystalline: These mid-grade solar panels split the difference between monocrystalline panels and thin-film panels in terms of both cost and efficiency.
• Thin-film: These solar panels are generally the most affordable type of solar panel, but they’re also the least efficient and have the shortest average service life.

Additional factors, like roof size, the number of panels in the system and the hours of sunshine available, also impact how much energy a solar array can produce. However, there’s not much you can do about your roof size or available sunshine other than moving.

» MORE: Types of solar panels

Are solar panels worth it?

If you're trying to decide whether solar panels are worthwhile, weigh the cost of your purchase and installation against the long-term savings your solar panels can provide.

Solar panels can help offset your energy usage and produce your own power. In this way, "consumers can avoid paying high energy bills and gain greater budgetary stability," according to Tim Deters of Green Ridge Solar, a local solar company in Oregon.

Deters went on to say that investing in solar energy allows homeowners to "lock in the cost of their energy." Since energy costs have an inflation rate of about 4% per year, this saves people money over time.

Once a solar installation is paid off, your energy bills will be a thing of the past.”

According to Deters, many who choose to finance their systems can lock in payments at or below their current electricity costs. This means beating the rate of energy inflation and potentially achieving independence from a utility company.

"You will be paying that utility bill for the rest of your life until you die, or you find an alternative way of producing your own power," said Deters. "Once a solar installation is paid off, your energy bills will be a thing of the past."

One caveat to keep in mind: Solar panel cost — and quality — vary from one company to the next. Lower prices may correspond to substandard installation and poor customer service; higher prices may correspond to a turnkey installation experience.

These factors and others, such as references, reviews, customer service and solar panel quality, should all be taken into consideration to make sure your solar panels are worth the investment.

What about maintenance costs?

According to Deters, there are few long-term or ongoing costs associated with solar power. Solar panels have no moving parts and are often warrantied for 25 years. Often, solar panels are guaranteed to produce 80% to 90% of their original power output over the warranty period.

Solar panel cleaning

Solar panels only need to be cleaned about once every six months, and they otherwise have few or no ongoing costs — unless you need to replace your roof. During a roof replacement, the solar installer will need to take your solar panels down, store them for the duration of the roof replacement and then reinstall the solar panels once the roof is replaced.

These costs vary depending on the size of your solar array, the length of time the panels must be stored and other factors.

Should you go solar?

The decision to go solar is different for everyone. Some factors to take into consideration include:

Home size and energy usage

Bigger homes tend to use more energy, and the more energy your home uses, the larger your solar array will have to be. Bigger arrays typically cost more — but also have the capacity to make a bigger dent in your average monthly utility costs.

Budget

While solar panels can save you money over time, the upfront costs can be steep. This may prohibit some homeowners from investing in solar technology. Solar financing, solar leases and solar PPAs can spread costs out over time, so talk to your solar installer to find out what options are available to you.

Sun exposure

Sun exposure makes a big difference in the number of solar panels your home needs, and the amount of sun your home gets depends on several factors, including the design of your home, its location, the local climate and whether there are any nearby trees or buildings casting shade on your home.

According to Deters, your solar installer may ask, "How many roof obstructions are there (chimneys, skylights, vents, dormers, ridges, valleys, etc.)? How much shade does the roof receive (shade obviously isn't conducive to solar)? Which direction does the roof face (south is best, but east and west are also suitable)?" and so on to help determine your sun exposure.

Availability of solar incentives

Although the federal solar tax credit is available nationwide, the availability of other solar incentives varies. Homeowners who live in areas where solar incentives are widely available may find investing in solar more attractive than homeowners who do not have access to as many incentives. Check in with the appropriate local and state government offices for information about incentives where you live.

Energy-consuming appliances and vehicles

The more energy you use, the more you have to gain by going solar. Home appliances and your heating and cooling systems have a major impact on your energy bill, but so can electric vehicles and other large electronic devices.

We followed up with a recent reviewer on ConsumerAffairs about their experience going solar, and they claimed that owning an electric vehicle and a plug-in hybrid played a role in their decision to get solar power. "Both increased our electricity consumption, so we had to research our solar options," they said in an interview.

Bottom line

How many solar panels a home needs depends on several factors, including home size, sun exposure and panel type. If you have an average-size home, your installer may determine that 19 solar panels is about right. To ensure your home is properly outfitted with the correct number of solar panels, work with an experienced installer that has a good reputation, solid customer service practices and a great warranty.