As solar energy rapidly gains popularity, one of the most important and complex questions every potential solar customer has is, “How many solar panels do I need?” Based on our customer surveys, the average house needs around 16-25 solar panels to power its typical energy consumption.
The number of solar panels you need is important because it largely determines the total cost of your solar array. However, the answer is based on a number of individualized factors like household energy use, home location, roof size, roof angle and more. Though a solar professional can visit your property to assess your roof and decide the appropriate number of panels, you don’t have to go into the process blindly.
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How to Calculate the Number of Panels You Need
There are a few factors to consider when calculating how many solar panels you’ll need for your home. You’ll need to know your average annual energy consumption and how much energy your solar panels can generate. Exactly how much solar power each of your panels generates will depend on the average number of peak sunlight hours in your area, solar panel efficiency and your roof’s conditions.
Below is the equation for estimating how many solar panels you will need. We’ve broken it down into steps so you can plug in your household’s numbers. If you don’t know exactly how much energy you use or how much your preferred panel generates, you can substitute with the following U.S. household averages:
- Average annual U.S. household energy needs: 10,632 kWh
- Average daily peak sunlight hours (when sunlight intensity is at least 1,000 watts [W] per square meter): 4 hours
- Average solar panel wattage: 350 W (high-efficiency panels can generate 400 W or more, whereas less efficient panels may generate 250 W or less)
Calculate the Number of Solar Panels You Need
The following tool will allow you to determine the number of solar panels you will need to power your home. To start, you will need to figure out your annual household energy consumption in kWh and input it into the field below.
How Many Solar Panels Are Installed on Average?
According to our 2023 poll of 1,000 homeowners with solar, the average homeowner installs between 16 and 25 rooftop solar panels. If you want a personal estimate of how many solar panels you’ll need to power your home, there are several online resources available.
The National Renewable Energy Laboratory (NREL) created the PVWatts tool to automatically estimate the upfront cost and energy production of solar panels on any roof in the world. You can adjust the number of panels, along with other variables, to create an estimate of the yearly energy output of your solar array.
Additionally, energy.gov has resources to answer questions you might have about going solar, including the average cost of converting to solar energy, how solar helps offset your energy bills, and how to take advantage of solar incentives and tax credits.
Real-Life Experiences with Solar Installations
We spoke with several homeowners with solar arrays on their homes. Below are some first-hand accounts of the solar installation process.
Here’s what Nadzeya Sankovish, a journalist and researcher at Health Reporter, shared about her experience:
“I have 18 solar panels on our home. It is enough to power the home because our consumption per month is approximately 1,000 kWh.
The solar contractor did contact us and talk about the roof and household needs. They calculated the [energy] amount we consume and the number of solar panels we need. So whenever someone calculates and gives you a number, always ask the question: Have they considered additional use of electricity in the future? The reason is, our consumption can increase in the future. And sometimes with situations like COVID-19 and lockdown, your consumption could just boost up because you are staying at home for more time. In my case, the calculation was good enough.”
Rinal Patel, the founder of Suburb Realtor and a homeowner, also had solar panels installed:
“I invited a solar panel contractor who, after requesting to have a look at my roof, estimated that I [needed] 13- 23 panels … Following his advice, I paid for and had 20 solar panels delivered to my home address before his arrival. After the solar panels were installed, I must admit that I still nursed some doubts as to how they could offset a load of electricity bills completely.
However, I was pleasantly surprised to discover that they were indeed sufficient. Seeing as my house is positioned directly in an area that allows sunlight, my panels are usually charged enough to power more than just my fans, lightbulbs and air conditioners — they also prove to be capable enough to provide for all of my household electrical needs.
However, as the durability of a solar panel largely depends on how much sun it gets regularly, I find that their efficiency is seasonal to a very large extent but certainly worth it.”
Factors That Determine the Number of Panels You Need
Your personal energy use, the size of your home and the angle, shading and orientation of your roof are key factors in determining how many solar panels you need.
Energy Consumption
If you want your solar panels to generate enough energy to power your home, you’ll first have to consider the amount of energy you use. As a general rule, larger homes and homes with more residents will consume more energy. However, high-efficiency appliances and home systems can simultaneously decrease your energy usage.
All in all, the less energy your home uses, the fewer solar panels you’ll need.
The average household in the U.S. consumes 886 kilowatt-hours (kWh) of electricity per month, or 10,632 kWh of electricity per year. To generate that much electricity, the average U.S. household would need about 15 to 20 solar panels. However, this number varies by state and individual needs.
To estimate your average yearly electricity usage, add up your kWh per month consumption from your utility bills over the past 12 months. It’s best to know your energy usage over at least a year so you can account for seasonal changes and build an understanding of your average use. Your solar contractor will also average your monthly electric bills to determine how large your solar panel system should be.
Angle, Shading and Orientation
The amount of sunlight your roof receives is a crucial factor in determining whether or not your roof is suitable for solar panels. A roof that receives full sunlight will be better for generating solar energy than one that is shaded. If part of your roof is shaded most or all of the time, you may not be able to utilize that space for your solar panel installation.
The ideal angle and orientation for your photovoltaic (PV) system depends on where you live. If you live in the U.S., which is in the Northern Hemisphere, the general recommendation is to orient your panels facing true south. You don’t necessarily need a south-facing roof if you’re installing a solar energy system, but it can help optimize your solar panel output, which in turn maximizes your energy production.
According to the U.S. Energy Information Administration, the optimal angle of your solar panels is typically equal to your home’s geographic latitude. So if you live at 30 degrees latitude, your solar panels will be installed at a 30-degree angle due to the position of the sun in the sky.
The sun is lower in the sky at higher latitudes, which means solar panels are installed at a greater angle to receive direct sunlight. But the sun is higher in the sky at lower latitudes, so solar panels are positioned at a lower angle to receive more sunlight.
We recommend hiring a locally-based solar installer because they will know how to properly install your solar panels to maximize potential based on your location. Your solar contractor should discuss the angle, shading and orientation of your roof before installing your home solar system.
Roof and Solar Array Size
The size and condition of your roof can be a constricting factor when determining the size of your solar array. Your roof may seem spacious, but if it has shaded areas, a chimney, a skylight or other features, you may actually have limited space.
If you have a smaller roof, you may need to use higher-efficiency monocrystalline panels instead of the slightly less efficient polycrystalline panels. Higher-efficiency panels will be more expensive, but you’ll need fewer panels to power your home — because they’re more efficient, a monocrystalline solar array will generate more energy than a solar polycrystalline solar array of the same size.
Thin-film solar panels are the cheapest option but are rarely used for residential solar projects due to low efficiency. Most homes simply do not have enough roof space to accommodate the number of panels needed to generate adequate power using thin-film solar cells.
Your solar contractor will assess your roof and advise you on what type of panels you should use. Every roof is different, so it’s best to talk to a professional.
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Frequently Asked Questions About Home Solar Panels
The average U.S. household needs between 15 and 20 solar panels on its roof to generate enough electricity, or around a 9 kW system. That being said, the number of panels needed depends on the amount of power a household uses. To determine how much electricity you use annually, average out the usage on your power bills from the last 12 months.
A 2,000-square-foot home typically needs between 15 and 25 solar panels. The exact number depends on your home’s electricity needs. If multiple residents are living in a 2,000-square-foot home, they may consume more electricity compared to an individual or couple. In this case, they might need more solar panels.
If you are planning to go completely off-grid, you must ensure that you have enough solar panels to adapt to your needs throughout an entire year. Panels usually generate less energy during the winter, which you should plan to accommodate. You’ll want to invest in a backup solar battery and inverter to store and use excess energy in times of need.
The average U.S. household needs about 15 to 20 solar panels to generate enough energy to offset its energy use.
You can learn more about different types of residential solar panels by reading our guide to the best solar panels for homes.
If you have feedback or questions about this article, please email the MarketWatch Guides team at [email protected].
