Solar energy is having a moment in D.C., after years of efforts to get more people to make the switch.

There were more than two times as many solar installation permits issued in the District in fiscal year 2019 compared to the previous year, and more than three times as many permits as fiscal year 2015.

“It’s taken a long time in the District for people to gravitate towards solar,” says Mark Ballantine, executive director of D.C.-based solar installer Universal Renewables. “I’ve noticed a very big uptick in interest, probably in the last three years.”

There are a few likely reasons behind the uptick—for one thing, D.C. has recently strengthened its renewable energy mandate, which includes a specific requirement for how much electricity in the city must come from local solar (increasing every year, from 1.85 percent in 2019 to 10 percent in 2040). That mandate creates a strong local market for solar credits, making solar systems more affordable for homeowners and profitable for solar businesses.

“It’s very strong, probably one of the strongest in the country,” says Ballantine.

Another reason there are more solar permits: It’s gotten a lot easier to get one. “Local permitting is a big factor when residents make a decision on any construction,” says Ernest Chrappah, director of the District Department of Consumer and Regulatory Affairs, which is responsible for building permits, including solar.

“If there are long waits, high costs, excessive inspections and lots of paperwork to do, it deters people,” Chrappah says.

About five years ago, DCRA changed its solar permitting process to speed things up.

“The solar permitting process was particularly unpopular with the solar industry,” says Dave Epley, who manages DCRA’s green building division. “Solar was part of normal building renovations. For that reason, it was getting lumped in the same cue as large office renovations, so the delivery was really behind.”

Ballantine can attest to the unpopularity of the old permitting system. “It used to be, you’d walk the plans through the permit desks,” says Ballantine, who spent many hours waiting in line at DCRA. “It was just a very clunky process.”

Now permitting is done online—installers can upload plans and photos and get a project approved without an in-person visit. “I would say it’s cut the time down probably by half, for me,” says Ballantine.

This story originally appeared at WAMU.