For backup power, batteries join the mix as prices come down

The Brightbox system stores power generated by a home’s solar panels for use later.Sunrun

For decades, New England homeowners have turned to natural gas- and diesel-fired generators as a way to keep the lights on after storm outages. Battery power emerged in recent years as an expensive alternative, but it’s been too pricey for most consumers.

That could be about to change.

San Francisco-based solar installer Sunrun Inc. has begun selling its home-battery package, known as Brightbox, in Massachusetts for an introductory battery price of $1,000, a fraction of what rival battery installations cost.

Businesses have been the primary audience for building-scale batteries in the past. But the emergence of Sunrun’s relatively low-cost option is a sign that energy companies are starting to get aggressive about wooing consumers, too.

“Three years from now, it’s going to be pretty prevalent,” Richard Baxter, a Boston-area storage consultant, said of home batteries. “The market will keep growing, because those costs are coming down and incentives will grow. All of a sudden, you’re going to get to a point where it’s cost-effective for most people to put in these batteries.”

In Sunrun’s case, the company hopes to capitalize on local residents’ fears of extended power losses after a storm hits. Sunrun planned the announcement of its Massachusetts launch before last week’s nor’easter hit. But its press release on Tuesday plays up the fact that the storm caused hundreds of thousands of customers in Massachusetts to lose electricity.

“If you had Brightbox before this last storm, you would have had power through the storm,” said Chris Rauscher, a director of public policy at Sunrun.

With a Brightbox system, you need to install a Sunrun solar system on your roof. Often, Sunrun ends up owning the panels, but consumers save on their electricity bills over time by using the power that’s generated by the panels.

Solar panels typically turn off when power to a home is lost, but they can stay on if the electricity they generate can be stored in a battery on-site. A spokeswoman said the Sunrun systems — the company largely uses lithium-ion, wall-mounted batteries manufactured by LG — can store as much as 10 hours of power and then can be recharged by the homes’ solar panels.

Sunrun is now selling Brightbox in six states. Sunrun executives say they picked Massachusetts, in part, because of the frequency of storm-related outages and because state officials are trying to encourage the proliferation of storage through grants and incentives.

“We’re at this tipping point with batteries,” Rauscher said. “With solar-battery service, you have an edge over generators. There are no fumes, there are no carbon dioxide emissions, there are no fuel costs.”

But home batteries have also been much more costly, with prices that can total $10,000 or more for a full installation.

“It’s very expensive backup power if it’s going to run once, twice, or three times a year,” said Sean Becker, who runs an energy storage company in Somerville called Sparkplug Power. “That’s changing as lithium prices decline.”

Tesla, the best-known of Sunrun’s rivals in this state, started selling its Powerwall system last year in Massachusetts. It can cost $6,600 for the equipment, plus $800 to $2,000 for installation. The Tesla batteries, a spokeswoman said, can be installed without a solar connection and offer other advantages over the LG batteries that Sunrun sells. Tesla and National Grid recently won a $1.25 million grant from the Massachusetts Clean Energy Center to install Powerwall batteries in 500 homes on Nantucket.

Daniel Buonomo, an accountant who lives in Mattapan, is among the Sunrun customers who are weighing whether to add a battery system to the mix. He said he installed Sunrun solar panels on his roof last year, and they’re saving him $70 to $80 a month. “The idea of saving money in terms of credits against the [electric] bill is great,” Buonomo said. “But I also like the idea of reserving the power so ultimately you can, over a period of time, tap into it.”