Aerial view of a home with a roof mounted solar system

Is Your Home Right For Solar?

We get a lot of questions about how solar works, but one of the most important questions you can ask is whether your home is right for solar. Although we’d love to see every home in North Carolina powered by a solar system, the reality is not every home is a qualified candidate. Between NC’s big beautiful pine trees and the infinite ways homes are designed and constructed, there are many factors that determine whether a home will be a good contender for solar. That’s why we’re sharing our home solar potential checklist to help you along your solar journey so you can make a smart solar investment.

Home Solar Checklist

When evaluating your home’s solar potential, we look at six primary indicators:

  • Space
  • Shading
  • Location
  • Orientation
  • Tilt
  • Roof Age

While some factors have stronger solar implications than others, finding the right balance between how each of these areas impact the other is important for maximizing your solar savings.

1. Space

We need a reasonable amount of unshaded space to put a solar system on your roof. An average 4-6 kW system (16-24 panels) will need 200-400 square feet. Beyond shading, vents, dormers, and other elements of your roof structure can limit the amount of space we have to work with when designing a solar system for you. There are also several other criteria that we look for in a roof to capture the maximum sunlight over the course of the year. We’ll dive deeper into these in a moment.

Source: https://www.nrel.gov/docs/fy04osti/35297.pdf

If your roof has limited or shaded roof space, don’t worry! We can install a ground mount solar system as well. The biggest benefit of going with a ground mount system is that shading can be avoided. Since ground mounts are not limited by roof size or orientation, you may have more options when it comes to designing a system to meet your solar goals. We have some creative install methods, so you will have plenty of choices for how the system looks whether it’s a carport, pergola, low ground-mount, or something else!

2. Shading

Shading is public enemy #1 when it comes to solar production. While solar cell technology has evolved to produce energy from the diffused light present on overcast days, energy cannot be generated in *complete* shade. Shade can come from many sources but when it comes down to it, the real MVP of shading is trees.

This is why an onsite assessment of your home (and trees) is so important when going solar. While satellite imagery has come a long way, those views can be outdated or misleading, and do not account for future growth of surrounding trees. The best way to gauge exactly how shading will impact your solar potential is by having a solar technician come to your home to evaluate whether we can position your solar array to avoid shading or if you’ll have to cut back or remove trees to make solar feasible. We typically do not like to recommend tree removal (we love trees!), but we also want you to have optimal solar production and will list it as a potential solution.

SUNEYE

How does a solar designer know how much shading your home will have? The answer is simple and reliable. We use a device called a SunEye that allows us to determine the solar potential of a roof. Its name is fitting as it has a fisheye lens that assesses the total solar production of a site based on the shading of the area. This includes simulating if shading elements are added or removed in addition to giving information about the roof pitch and azimuth angle. The SunEye can also take into account the tilt and orientation of possible solar panels for a full scope of your solar potential.

3. Location

The amount of solar energy that hits an area (also called solar irradiation) depends on its distance from the equator and local weather conditions. For example, according to the National Renewable Energy Laboratory (NREL), North Carolina averages around 4-5 kilowatt hours of solar energy per square meter. This is more than the < 4 kilowatt hours per square meter that Alaska receives since Alaska is further from the equator. But this is also a little less than the American Southwest — which averages 5-6 kilowatt hours per square meter — despite the fact that we are similar distances from the equator since the Southwest has less precipitation throughout the year.

This map from NREL shows the average solar irradiation for the United States.

Solar Irradiance map of the United States
Source: https://www.nrel.gov/gis/solar.html

As you can see in NREL’s North Carolina specific map, solar irradiation is fairly constant across our state with the Great “Smoky” Mountains really being the only place where solar potential drops a little.

Solar Irradiance of North Carolina
Source: https://www.nrel.gov/gis/images/state-level-resource-maps/dni/North-Carolina-DNI-2017-01.jpg

4. Orientation

Azimuth (pronounced az + uh + muhth) is the fancy solar industry term we use when referring to the cardinal orientation (north, south, east, west) of your solar array. Because North Carolina is in the Northern Hemisphere, sunlight hits from a southern angle. As a result, a solar system needs to be installed facing south to be optimized for solar production. You can see how the sun remains in the south, even as its position in the sky changes throughout the year, in this diagram:

Seasonal changes of the sun's positioning
Source: https://www.nrel.gov/docs/fy04osti/35297.pdf

A perfectly south facing system would have an azimuth of 180° south. While south facing systems are optimal, the azimuth angle can be range by 90° east or west and still receive a highly productive amount of sunlight. Production only really starts to drop off when we face panels northward (so we avoid that in 99% of cases). Check out the differences between azimuth angles in the chart below.

Solar potential based on roof orientation
Source: https://www.nrel.gov/docs/fy04osti/35297.pdf

5. Tilt

A solar panel’s tilt is its angle relative to the ground. For a roof mounted solar system the tilt will equal the roof’s pitch (unless it’s a flat roof). Roof pitch is commonly measured on a rise-over-run ratio, so your roof pitch may be 6/12 or 7/12. Most homes typically range around 4/12 to 9/12 which translates to 19° to 37°. The ideal pitch for a solar system in North Carolina with an azimuth of 180° is between 30° and 35° or a 7/12 to 8/12 roof pitch. As a solar system’s azimuth gets further away from south, flatter tilts are more advantageous. This psychedelic graph from Solmetric (the company that makes Suneye) shows the impact of tilt and azimuth on optimal solar production for Durham, NC.

Source: https://www.nrel.gov/docs/fy04osti/35297.pdf

For ground mount solar systems we aren’t tied to a predetermined roof pitch so we can set the tilt to the optimal 30°-35°. For flat roofs systems, however, we generally limit the tilt to below 15° in order reduce the array’s exposure to wind. You can check out the optimal azimuth and tilt for your location with Solmetrics calculator.

6. Roof Age

If you think you will need to replace your roof in the very near future, we recommend doing that before installing solar panels. But if your roof can hang on for another 2-3 years you might consider installing solar now to take advantage of current rebates and incentives, and to reap the benefits of your solar savings over those years. Don’t forget 2019 is the last year for the full 30% federal tax credit before it starts stepping down in 2020.

When you do need to re-roof, give us a call and we’ll simply take the panels down but leave the racking up. The roofers will reflash all the feet, and then re-shingle. Afterwards, we’ll put the panels back up and you’ll be capturing your solar savings again! 

If your roof is fairly new or in good shape, now is a great time to go solar. The panels will actually protect the roof, and when it comes time to re-roof we may not have to take down the modules and you can replace shingles around it.

If you have any questions about your roof, our solar designers will take a look at it during your on-site assessment and give you a recommendation.

A Note About Online Solar Estimate Tools

There are plenty of online solar estimate tools and calculators out there like Google’s Project Sunroof and Solar-Estimate. These are great tools to give you a general idea to get started on your solar journey, and many of them will connect you with nearby solar professionals. However, designing a solar system based on limited factors like home’s square feet will not give an accurate representation of what size system is needed to meet that home’s energy needs.

Ultimately, an in-person on-site assessment is really the best way to get an accurate estimate of your home’s solar production potential and what the savings will look like for you based on your specific site and historic energy use.

What's Next?

Still wondering whether your home is a good fit for solar? That’s what our solar educators are here for! Reach out and let us know you’re interested in getting a free solar evaluation for your home.

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Primary Solar Form 2019 - Placeholders