Whether you’re aiming to reduce your home’s energy usage throughout the day or you’re simply looking to see a little less of your paycheck go to utility bills, installing solar panelson your roof has likely crossed your mind. And you wouldn’t be the only one.

As of early 2016, more than 1 million homes in the U.S. had solar panels installed on their roofs, according to the Solar Energy Industries Association. It’s a small percentage of the total homes in the U.S., but a growing number nonetheless.

“For the vast majority of home shoppers … it ranks among the nice-to-have-but-not-essential things to consider,” says Aaron Terrazas, an economist for real estate information company Zillow.

A house’s potential to benefit from a solar panel system – or photovoltaic system – can even be a part of the house hunting process. In November, Zillow partnered with solar data information company Sun Number to display a home’s potential for solar power on the property’s profile – factoring in the sun exposure, regional weather patterns and roof pitch, among other things.

As the Sun Number indicates, on a scale of 1 to 100, not every home is ideal for getting a maximum benefit from solar panels. And while the score is calculated using key details of a property and its location, other factors can also make installing a PV system an unwise investment.

But if you’re a homebuyer looking to incorporate alternative energy solutions into your next house, the kind of preliminary evaluation the Sun Number provides is “definitely a place to start,” says Tim Treadwell, director of engineering, research and analysis at the Center for Sustainable Energy.