If you’ve shopped for solar before, you may have come across something known as “Sun Number”, or sun score. Like EnergySage, Sun Number received funding from the Department of Energy’s SunShot initiative to innovate in the solar energy space. Read on to learn more about how a property’s Sun Number is calculated and what your sun score means for going solar.
NOTE: Sun Number’s website is no longer functional, and Sun Number scores no longer appear on Zillow. The tool looks to have been sunsetted recently.
- A Sun Number (or sun score) is a way to measure how suitable a home is for solar
- Sun Number uses aerial imagery and factors like shading, trees, regional climate, roof shape, and more to come up with a score
- You can check your property’s solar suitability with our Solar Calculator, and compare solar quotes by registering for free on the EnergySage Marketplace
What is a Sun Number score?
A home’s Sun Number score is a measure of its suitability for solar, on a scale from 1 to 100. The methodology behind the score was developed by the company Sun Number, a recipient of a grant as part of the Department of Energy’s SunShot Initiative.
Importantly, just like any measure of solar suitability, your property’s Sun Number is only one data point to consider. Solar installations are unique to each home depending on electricity usage, location, pricing, and more, and it’s always best to compare solar quotes to best understand how feasible solar is for you. To get started comparing solar quotes from local, qualified installation companies, register on the EnergySage Marketplace for free today.
Sun Number score components
Sun Number scores take into account four main categories of factors to create a total score. The categories are all weighted differently, These categories are:
- Electricity rates
- Cost of solar
The “building” score category for a Sun Number is the most extensive and detailed part of the rating system. There are several factors that contribute to this portion of a sun score, including roof design, roof size, roof pitch and orientation, and shading, all of which Sun Number generates from aerial roof imagery. In general, a south-facing roof with lots of space, no shade, and an angle matching the latitude of the property’s location is the best kind of roof for solar, and will receive a high building score as part of its overall Sun Number.
This is the same type of information that powers the EnergySage Solar Calculator! We use roof data, sun exposure data from Google’s Project Sunroof, and our own market pricing data to estimate how suitable your home is for solar, and how much you could save.
The next three score categories that factor into a total Sun Number are more straightforward than the building score, starting with climate. Different areas of the country receive different amounts and intensities of sunlight, so a home’s solar suitability is therefore related to the region it is located in. For example, in higher latitudes like the Northeast or Pacific Northwest, sunlight is, on average, weaker throughout the year than it is somewhere like Texas or Florida. More sunlight throughout the year leads to a higher climate portion of a Sun Number score.
Sun Number gets their solar radiation data from the National Renewable Energy Laboratory (NREL).
Installing solar panels helps you save on electricity bills, so it follows that places with a higher cost of electricity are more suitable for solar installations, as those installations will have a shorter payback period. Sun Number factors this into their total score: higher average electricity rates means a higher sun score, and lower average electricity rates mean a lower sun score.
Cost of solar
Lastly, just like a high cost of electricity makes an area more suitable for solar, so does a low cost of solar. A total Sun Number score takes into account the local average cost of solar – lower average costs mean a better sun score, and higher average costs mean a worse sun score. The reasoning for this is the same as the reasoning behind how electricity rates impact your sun score, just in the opposite way. Low costs of solar means your upfront solar installation price is lower, therefore it will take less time to make back the money on your initial solar investment. Conversely, a high upfront cost of solar means it will take, in some cases, several more years to make back your initial solar investment.
Can you go solar with a low Sun Number score?
Using a tool like Sun Number to understand your property’s suitability for solar can be an important initial step in any solar journey. However, it’s not the only data point you should consider, and a low Sun Number score doesn’t mean you shouldn’t consider solar!
Once you’re ready to start comparing solar quotes, you can register (for free!) on the EnergySage Marketplace. We’ll get you connected with qualified, pre-vetted solar installers in your area, and you can compare quotes from those companies right on our platform, completely online.