Zillow is introducing the idea of rooftop solar to millions of consumers and real estate professionals who might otherwise be unaware of its value.

Homebuyers and sellers are becoming more aware of the value of rooftop solar panels — not just for ecological reasons, but for energy savings as well — and now there is a quick and easy way to estimate that value. Zillow has partnered with two startups, Sun Number and Wave Solar, to include Sun Number’s proprietary rooftop solar scoring system on 84 million properties on Zillow nationwide as of today.

That’s up from 40 million buildings on Zillow that had a Sun Number listed as of last year.

Sun Number’s methodology is complex, but the idea is simple. The tech startup has developed a 1-100 scoring system that provides homeowners with a measurement of how good their rooftop is for solar.

Sun Number already makes solar scoring available to anyone who enters most U.S. addresses into the Sun Number website. The problem is that until now, the score only informs people who visit the website because they are already interested in the potential value of rooftop solar.

The Zillow partnership represents a quantum leap forward in public awareness. By expanding to another 44 million home entries on its website, Zillow is introducing the idea of rooftop solar to millions of consumers and real estate professionals who might otherwise be unaware of its value. The Sun Number is available on Zillow if you scroll down on a property page.

Sun Number on Zillow listing

That broad public awareness angle is the raison d’être for Sun Number. The start-up launched in 2012, in collaboration with the US Department of Energy’s “SunShot” program, which was designed to help lower the cost of installing solar power. The initial aim of solar scoring was to help urban planners understand the impact of rooftop solar on a citywide basis.

In an interview with Inman, Sun Number co-founder David Hermann explained why the company expanded its mission to include the general public:

“Once we started analyzing roofs, we also recognized that homeowners needed to be educated on whether they should explore solar for their home and developed the Sun Number score as an easy-to-understand rating between 1 and 100.

“I hope that Sun Number can contribute to a national movement by home and building owners to combat climate change and invest in our world’s future by installing solar on their roofs.

“We need to recognize that individually one solar installation may not seem like much, but when we all install solar it can make a difference in the world. When we all work together toward the collective good, we are a powerful force.”

Keep an eye out for further developments. Hermann has big plans for engaging the public in clean energy:

“Our goal was always national coverage, but there were many obstacles in our path and it was never a given that we would reach our goal. Today, far from resting on our accomplishments we have a long list of enhancements that we want to implement in the future.”

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