California will be the first state in the U.S. to require solar panels on all new homes starting 2020, but the legislation’s passage did not end the debate over a key question: Does the cost of installing solar pay off for homeowners?

Some developers are not even waiting for 2020 and are pressing ahead with solar-powered homes for what they say is the best reason: it is simply what best serves the homebuyer market matching energy demands to efficiency and cost. The state estimates the new solar power rule will help homeowners save about $19,000 in a 30-year period. Others say the mandate will push up housing costs too much for many homebuyers.

There’s another way to look at the question: Does adding solar power increase a home’s value at time of sale? According to real estate information company Zillow, in some states the answer already is yes. Zillow’s research indicates that in the same way homeowners are willing to pay thousands of dollars for renovations like a new kitchen or finished basement, they need to evaluate the return on investment from investing in solar energy.

Installing solar panels in a home not only helps to reduce current monthly utility bills; it can potentially increase the home’s value by up to 4.1% more than comparable homes with no solar panels, according to recent solar research done by Zillow — or an additional $9,274 for the median-valued home in the U.S.

Read more: Solar power can boost your home’s value — especially in these 10 states