Rooftop solar has become a hot topic in the recent decade as solar panels have come down in price to the point where you can see a return on your investment in as little as 24 months. Currently, about 1.5% of homes have solar panels installed on the roof removing the need for about 14 TW hours of power from utility companies. While this may seem like a drop in the bucket compared to the 4,090 TW hours required to power the country, it’s up considerably from the approximately 1 TW hour it was displacing 8 years ago.

Now, according to an NREL study, putting solar panels on every residential rooftop in the U.S. could generate around 920 TWhs of electricity, enough to take care of 25% of the power needs for the country. Expand that to all residential and commercial buildings and it comes closer to 1,450 TWhs, or almost 40% of electricity used in the U.S.

What exactly would it take to get anywhere near 100% solar saturation for homes? Tax credits have helped and they are promoting the expansion of the technology but 1.5% is still paltry compared to what we could be looking at.

Requirements for homes being built to include at least some solar panels have passed in a few cities in the U.S. such as San Francisco. Austin, TX is mulling over a requirement providing for something similar. The geography of the land and the weather west of the Mississippi River makes it possible for many of these building to recoup their higher initial costs withing a few years, not to mention the value that solar panels add to a home.

Having homeowners cover a good portion of their own electricity needs with rooftop solar panels would likely go a long way in reducing the nation’s appetite for fossil fuels. In the past, when the economy has taken a dip, so has electricity usage. That trend seemed to change in 2015 however when the U.S. economy as a whole was doing alright but total electricity usage actually went down by about 2% in the U.S. Residential solar panels may taken a bite out of the overall total, along with advances in energy efficiency, transmission and conservation.

Ultimately, electricity isn’t prohibitively expensive for just about any place that is already connected to the grid. The combination of substantial savings on electricity bills, along with tax credits and at least somewhat of a return on the purchase price when the property is sold, could increase rooftop solar saturation considerably in the coming years.