Editor’s note: This is the second part in a three-part series examining how local governments use solar to reduce power bills while achieving environmental goals. Read part one here and part three here.
An unfortunate side effect of being a governmental organization serving more than 600,000 people: You’re bound to use quite a bit of electricity. And that means paying a little extra to the utility.
Washington, D.C., like many local governments, has long faced “peak demand charges” for using so much power. Essentially it pays the utility a certain amount to be ready to supply as much power as the city government will need on the day of the year when it uses the most.
And that’s a big part of the reason solar power can help save the district money, even if its portfolio of panels doesn’t come anywhere close to meeting 100 percent of its needs.
“Peak demand can increase the cost of our power purchase by a quarter to a third,” said Tommy Wells, director of the District Department of Energy and Environment (DOEE).
The city purchases power from 22.2 megawatts of solar-generating capacity right now — not including panels outside the district that it buys power from. But it has plans to install 11.4 more megawatts by spring 2017, according to DOEE Program Analyst Emil King. When all is said and done, the district will have panels on 49 building tops and parking lots, and some on the ground — enough to save $25 million over 20 years. The district is paying for it straight out of its capital budget.
And there’s room to grow that portfolio too. Many of the district’s schools are poor candidates for solar now because they’re going through modernization projects that involve new roofs. While the roofs are being installed, the district can make sure they’re solar-ready. Once the roofs are in place, the district can consider them for solar panels.
Like Yolo County, Calif., the District of Columbia can take advantage of net metering programs. That means it can sell power for as much as it would buy it for. That’s helpful on weekends, when the solar panels are generating electricity but many government workers aren’t in the office to use it.
Overall, the goal for D.C. is simply to shift demand. The district’s panel-crowned buildings get about 20 percent of their energy from solar, and overall the city government gets about 3.5 percent of its power from the sun. By producing energy on site, the government can shave off peaks in usage and bring its power bills down — as well as cut its reliance on electricity generated by fossil fuel-powered plants.
That’s an important part of the city’s motivation behind the panels as well. The city has been aggressive in its climate change efforts, joining the Compact of Mayors initiative to reduce greenhouse gas emissions. In June, the City Council agreed to source half the district’s electricity from renewable sources by 2032.
In the future, Wells said, he wants to work storage capacity into the city’s plans as well. By adding the ability to store solar power and dispatch it strategically, the city will truly be able to shift its demand on the grid to the times that make the most sense and save the most money.
“So the future, which we will probably have to pilot for others," he said, "will be how to pair solar with energy storage for the purpose of shaving peak demand usage."