If you’re looking to invest in solar energy, you’re probably wondering how many solar panels you’ll need to power your home.

That answer depends on a variety of factors that we’ll talk about. First and foremost, you need to understand that the strength and efficiency of the solar photovoltaic (PV) energy system you invest in will ultimately determine the number of square feet that you’ll need on your roof to house it.

For the purpose of this article, we’ll use the number of kilowatt hours (kWh) used in 2017 by the average home – which was 10,399 kWh, per the U.S. Energy Information Administration (EIA).

In order to calculate how many solar panels you’ll need, you should first look into how much electricity you’ll want to generate from your panels. Using a solar power system that completely offsets your entire energy usage, may be unrealistic. Having a large system to cover all your electricity can be both expensive and take up a lot of space on your roof, which you might not even have enough of.

Therefore, it’s important to maximize the return you get on your investment. Even though many solar panels come in similar shapes and sizes – some outproduce others.

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An average home will need at least 100 square feet for a starter system. If you’re looking to go all-in and invest in a larger system, you’ll need something closer to 1,000 square feet of roof space. An average sized solar panel translates to 15 watts per square foot.

With these stats in mind, we can now calculate how many solar panels you would need. For the sake of this example, we’ll use solar panels with an output rating of 300 watts – which falls in the range given to us by Energy Sage. For an average home to produce 300 watts from its solar power system, it would need 20 solar panels. The equation is below.

15 watts per square foot x 20 solar panels = 300 watts

The number of solar panels and overall watts will vary depending on the panel’s efficiency.

Another major factor that affects the number of solar panels you’ll need is climate.

How your local climate will impact your purchasing decision.

Remember that we mentioned panel efficiency? Panel efficiency is the measurement of how much of the sun’s energy can be converted into usable electricity. Average efficiencies typically range between 15 to 18 percent.

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How does efficiency connect to climate? Well, if you live up north in a state like Massachusetts, where daily sunlight exposure is less than southern states, chances are you’re going to want a more efficient solar panel system. The additional solar output will help you generate energy despite receiving less sunshine than sunny states such as Arizona and Florida.

Another consideration is the positioning of your roof. Roofs that face south, offer the greatest window for productivity – due to the United States’ position in relation to the sun. If the southern facing part of your roof is covered by trees or located in a shaded area, you can still place your solar panels elsewhere, but their production will suffer from it.

If you’re looking to buy a home, there are markets in the U.S. where you can find homes with built in solar panels. As technology and awareness around solar energy continues to unfold, more homes will find themselves with solar power systems. The investment is clearly worth the reward. According to Solar Reviews, “If each home was to install enough solar panels to cover their electricity bill then on average the savings from installing a residential solar system in America in 2018 would run to $1,401 per year.”

Solar energy is continuing to expand its market share, making it more feasible to obtain with every passing day. Unless there’s a obstacle that makes it unrealistic to buy solar panels for your home – stop procrastinating and start saving.