What Is the Best Roof Design for Solar Panels and What If Mine's Not Perfect? | Solar.com

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What Is the Best Roof Design for Solar Panels and What If Mine’s Not Perfect?

If you’re looking to go solar at home, chances are you’re going to put those panels up on your roof. Ground-mounted solar is a great option, but it’s uncommon to have enough space to put up a decent-sized system in your yard. So that begs the question, what is the best roof design for solar panels?

Let’s get this out of the way first: Almost no one has the perfect roof for solar. Although some roof shapes and angles are better for solar production than others, solar panels are extremely versatile and can provide energy cost savings and carbon footprint reduction in a wide range of configurations.

In other words: Don’t let perfect be the enemy of good.

In this article, we’ll explore that makes a good roof for solar panels and some frequently asked questions.

Connect with an Energy Advisor to see how much sun your roof gets.

6 roof design traits that effect your solar production

There are several roof characteristics that effect how much your solar panels will produce. Here is the top six:

Orientation

Also known as azimuth, orientation is the direction your roof faces. For North American solar systems, the best roof design for solar panels is one with a large, unshaded south face (an azimuth of 180 degrees).

Not having a south-facing roof is not a deal-breaker. However, many roofs are multi-faceted, and if your roof is mostly west- and east-facing, you’re likely to only see a 10-20 percent reduction in the amount of energy you’re generating.

There’s been an ongoing debate about south-facing vs. west-facing panels over the last couple of years. While south-facing panels will generate the most energy, west-facing panels generate the most energy when demand is highest. That’s why some big proponents, including the California Energy Commission, encourage builders to include some west-facing solar panels in their developments.

In the end, south is best, but west and east are also good; having panels facing south and west will help you generate energy throughout the day.

Size

Along with orientation, the size of your roof will determine how many solar panels you can install. The average US home solar system size is 5 kilowatts or 12-13 panels with a rating of 400 Watts. With solar panels requiring about 15 square feet each, you need about 200 square feet of (south- or west-facing) roof space to fit 13 panels on your roof.

Shade

Big surprise: Solar panels only work when the sun is shining directly on them. If you’re surrounded by tall trees and your roof and yard are shaded most of the day, your choices are limited to either:

  • Taking down trees
  • Buying clean energy from a community solar system instead
  • Opting for a clean energy mix from your utility (if available)

It’s important to note that shading doesn’t always come from trees and outside objects — sometimes roofs can shade themselves. The best roof design for solar panels is one with minimal tiers and overhangs that could cause shading.

Material

What is your roof made of? The most common type of roofing material is asphalt shingles, but solar installers can put panels on just about any of the most common types of roofing materials, including tile, metal, slate and even wood shingle.

Some roof types are more difficult to install on than others, and if your roof is made of trickier materials it may add to the cost of your solar installation.

Age

More important than the roof type you have is how old your roof is. According to a study by the National Home Builders Association, an asphalt shingle roof should last for around 20 years, while slate, copper, tile, and metal roofs can last 50 years or more. Meanwhile, most home solar systems are guaranteed to last for 25 years, and will likely last much longer.

So if your roof will need to be replaced in the next 10 years or less, consider doing so before your solar panels are installed. You can always replace the roof after your panels are in place, but it involves removing the panels and racks, replacing the roof, and then re-installing the panels, which adds more cost to the project.

Pitch

The slope of your roof isn’t as important as the orientation, but it can affect your solar energy output. The ideal roof angle for power generation is about 30 degrees, but roofs that are too steep make installation difficult, while flat roofs mean that you can set the panels at just the right angle, but you’ll be paying extra for the required racking.

As a rule of thumb, your panels should be tilted at about the degrees as your latitude. So if you live in Los Angeles at 34 degrees north, then your panels should face south and be tilted about 34 degrees.

best roof for solar panels

Related Reading: How To Choose Solar Panels for Your Home

What if I don’t have the best roof design for solar panels?

Not everybody has a large, unshaded, south-facing roof. So what happens if your roof design is less than perfect for solar panels?

In these scenarios, there are two ways to increase your solar output:

Use panels with a higher power rating – Solar panels are rated from 250 to 450 based on how many Watts of DC electricity they can produce per hour. So, if you don’t have enough space for 16 250W panels, then you can achieve the same output with 10 400W panels.

Increase the number of panels – If you have limited sun exposure due to shading, pitch, orientation, or location you can simply add more panels. For example, Los Angeles averages around 6 peak sun hours per day while New York City averages around 4.5. That means it would require 15 panels to achieve 27,000 kWh per day in New York City, and around 11 panels to achieve 27,000 kWh per day in Los Angeles.

In both cases, you can expect your project to cost a little more than if you had a perfect roof for solar. However, the solar panels themselves make up a small fraction of your project cost, and adding or upgrading will have little effect on your energy cost savings over 25+ years.

Bottom line: There is no perfect roof

Although it’s tempting to want the best roof design for solar panels, solar panels are extremely versatile and can provide energy cost savings and clean energy in many applications.

Between the falling costs of solar equipment and the 30% federal solar tax credit, there’s never been a better time to go solar. Get started by comparing multiple quotes from vetted local installers.

Best roof design for solar panels FAQs

What type of roof is best for solar panels?

A south-facing composite asphalt shingle roof with plenty of space is typically considered the best roof design for solar panels. However, solar systems can be very versatile and provide clean energy and cost savings in a wide variety of applications.

What is the best roof design for solar?

It may sound simple, but a large square roof with a standard pitch between 20-30 degrees is ideal for a simple solar system. Roofs with lots of tiers with little extended space can create challenges for designers and installers.

What type of roof is not good for solar panels?

We hate to be the bearer of bad news, but if you have a slate or wood roof, your options are limited. Many solar companies will refuse to install on these materials, which can limit your options.

Some work-arounds include re-roofing with a new material or installing the system on the ground.

What if my roof is old?

Most roofs must be replaced at some point, but you have a couple options when assessing your roofs current state before going solar. If your roof is too old, some solar installers will replace your roof as part of the same project, which can help you save by combining the projects.

If your roof is getting old but not quite at point of replacing, it may be worthwhile to install the solar panels knowing you’ll need a roof replacement at some point down the road. In this case, re-roofing requires the added cost of having your solar company un-install and re-install the panels.

Solar panels can help aid the longevity of your roof, because they help protect against a lot of nature’s elements.

Will my roof have issues with leaks?

Leaks after solar installation are extremely rare. Yet, if they do happen it’s important to be covered by a warranty. Good installers offer extended warranties on workmanship, which means you won’t have to worry about being on the hook for any issues that could arise during an install.

If your roof seems like a fit, use Solar.com to receive free, no-obligation bids on a solar installation for your home.

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