LOWELL — In 2007, solar panels throughout Massachusetts could generate a total of three megawatts of energy, enough to power just shy of 500 homes.
Now, there’s a total capacity of 475 megawatts — enough electricity for more than 230,000 homes, based on figures from the Solar Energy Industries Association.
By 2020, state officials want to see 1,600 megawatts of solar. There are hopes that coal will no longer be a power source in Massachusetts by that year, and plans to make solar power inexpensive enough to get rid of state subsidies for it in the next decade.
Clean energy in Massachusetts, solar in particular, has grown significantly in the years since Evergreen Solar filed for bankruptcy and walked away from its Devens plant. But there’s still a long way to go in making efficient, environmentally friendly power an everyday staple, Energy and Environmental Affairs Secretary Richard Sullivan told The Sun’s editorial board this week.
The next steps are making sure renewable energy can be reliable and cost-competitive against the traditional, widely used fossil fuels like coal, oil and natural gas.
“Even with wind and solar, you still need a base fuel,” Sullivan said. “While we certainly want the cleanest energy we can have, I still need to have reliability in the system. People still want to be able to turn their lights on, people still want to be able to have their heat go up when they need it, so you still need a baseload.”
Moving forward, this energy base would most likely come from large-scale hydropower, Sullivan said.
A bill before the state Legislature would require power companies in Massachusetts to solicit bids from clean-energy generators for at least 18.9 million megawatts of energy each year. Sullivan said that would likely mean hydropower or onshore wind, generated somewhere in the Northeast.
But for now, around 50 percent of New England’s energy comes from natural gas. Sullivan said that’s an “over-reliance” on a fossil fuel that could hinder development of cleaner sources.
“You don’t want all of your energy coming from once source, because that makes you totally reliant on that one industry,” he said.
The failure of Evergreen Solar’s U.S. operations in 2011 underscored the importance of investing in a wide array of energy sources and companies, Sullivan said. The company, which had received government assistance, closed its Devens factory in 2011, costing 825 workers their jobs.
Sullivan compared investing in renewable energy to a 401(k) retirement account — the overall plan can be a success even if one asset fails.
“You would love all of your investments to be absolute home runs,” he said. “But at the end of the day, your goal is to have a number where you can retire at the standard of living you want to have. As long as you get there, that’s the name of the game.”
Pointing to double-digit annual increases in the number of clean-energy jobs for the last three years, Sullivan calls the field “a very fast-growing part of the Massachusetts economy.”
“We now have 5,500 companies doing business in Massachusetts in the field of clean energy,” Sullivan said. “Those 5,500 companies, not us government bureaucrats, project that there’ll be another double-digit growth in employees this year.”
A total of 84,000 people in Massachusetts — 2 percent of the work force — now work in the clean-energy field, in jobs related to energy efficiency, solar, wind and geothermal power, and similar industries.
About 9,000 of those jobs are in the solar industry, Sullivan said.
Throughout the state, 48 communities have installed solar panels on top of capped landfills.
Lowell has solar panels at the former landfill on Westford Street, as well as on four public schools, the Lowell Memorial Auditorium and two Water Department buildings. Combined, the solar projects are expected to supply 6 percent of the city’s electricity, or what would be used by about 775 households.
Chelmsford is moving toward a solar-panel installation at a former landfill off Swain Road, and Billerica last year signed an agreement with the owner of the Shaffer Landfill, where a 19,700-panel project is planned.
In the current phase of the state’s solar program, landfill installations are eligible for incentives, as are installations on municipal or state buildings and private homes.
“There are less incentives now for solar in, say, a converted field or a forested area where the trees are being shut down,” Sullivan said. “Through the public policy, we’re trying to line up where these are appropriate.”
Solar deployment in urban and low-income areas has been “one of the issues we have struggled with,” he said.
In apartment buildings and multi-family homes where tenants pay for their own electricity, property owners might not see a reason to foot the bill for a solar-panel installation.
“You need to somehow encourage the investment by the landlord, who isn’t necessarily seeing financial return immediately,” Sullivan said.
The state is planning to roll out additional incentives for homeowners, he said, including one that would offer low-cost loans for the purchase of solar-power systems.
As solar technology becomes more advanced and commonplace, the costs of producing the energy and installing the panels are dropping significantly, Sullivan said. That reduces the need for incentives and subsidies.
“It is going to take somewhere around 10 years to get us to where there are no subsidies for solar,” Sullivan said. “Overall, we’re well beyond the infancy stage, and probably into the mid-strides.”
Follow Katie Lannan on Twitter and Tout @katielannan.