Solar Power

How Much Roof Space Is Needed For Solar Panels?

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Two Palmetto solar installers adding solar panels to a home's roof.
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When it comes to residential solar panels, your home’s roof is the most obvious place to put them. But it’s easy to get confused about how much roof space is needed for solar panels to install a home solar power system. Not all roofs are constructed to the same size or specifications, and some homes have roofs with steeper pitches, while others have roofs with more faces. If you’re wondering “How Much Roof Space Is Needed For Solar Panels?” here are a few things to consider.

Solar powered homes with solar panels on various roof sizes and shapes.

There’s No Single Roof Size Answer

We’d love to tell you an exact amount of square footage that is required for a certain number of panels, but it’s not quite that simple. Each residential solar panel array is custom designed to match the homeowner’s needs, and the unique size, shape, and dimensions of each roof.

Energy Usage Determines Solar Roof Space Needs

How many solar panels you’ll need, and thus how much roof space you’ll need, starts with an estimate of how much power you use in a given year. There are plenty of ways to determine your annual energy usage, but the easiest is to simply take a look at your current monthly energy bill. It should tell you how many kilowatt-hours of energy you use in a given month, then just multiply that number by 12 to get an annual estimate. As a good starting place, the average American home uses about 11,000 kWh of energy every year.

Your Home’s Location Is Important

Different parts of the country get different amounts of sunlight. For instance, Arizona is famous for intensely sunny days. On average, Arizona gets 300 days of sunshine every year. Conversely, Juneau, Alaska, spends more than two-thirds of the year in darkness.

Depending on where you live, you’ll need more or fewer solar panels. So if you live somewhere with lots of sun, you might only need enough roof space for a few solar panels. But if you live in Juneau, you’ll need lots of solar panels on your roof to harness the available energy.

Your Solar Budget Is A Factor

Generally, larger systems are a great way to quickly offset your current electrical and fossil fuel energy usage. However, larger systems are naturally more expensive. While you may have the roof real estate for a large array, you might not have the financial budget for it, and vice versa.

Size and Rating of Solar Panels Matters

Solar panels can vary in size and rating, leading to different sized systems for the same amount of energy output. Some panels might be smaller but have a higher watt rating, which means they’re more efficient than a larger panel with a lower rating. The efficiency of the panels used in your solar power system will affect how many panels you need.

How Big Should Your Solar Array Be?

There are a few rules of thumb you can follow that can offer a general idea of how much roof space you’ll need for your solar power installation.

Generally, every square foot of roof space has the potential to generate about 15 watts of solar energy. Thus, a solar panel installation on a small home might only need around 100 square feet of roof space, while a larger home can require more than 1,000 square feet of roof space to properly offset electricity usage.

Most solar companies have found that the average American home typically needs around 18 to 24 panels to be effective. That is, of course, if everything about those panels is ideal, where the positioning is optimal, the panels are of a standard rating, and the location gets adequate sunlight year-round.

Maximum Roof Space Calculator

Most roofs will need a “solar panel setback” for safety. This setback is the open space between the edge of the array and the edge of the roof. The minimum solar panel setback varies from state to state, but generally, the setback will take up 25 percent of your roof’s usable space.

So if you want to get a sense of how many panels a roof can support, here’s an easy calculation you can do: Multiply the square footage of your roof by .75 to account for the setback. Take that number, and divide it by 17.5, which is the average square footage of one solar panel. The resulting number is the maximum number of solar panels you can fit on your home’s roof.

Roof Space For Your Solar-Powered Home

There are a lot of factors that go into designing a solar power system, including the arrangement and installation of the panels on your roof. Fortunately, Palmetto can help figure out the precise number and type of panels that will work best for your home and your family’s needs.

To find out how many panels your roof would need, get a free solar estimate, and a Palmetto solar expert will help design a system that’s just the right size to meet your energy goals.

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