Tesla PowerwallHot summer days aren’t when you’d think of needing battery backup power for your home – you might instead picture the aftermath of heavy winter snows and winds, with your next-door neighbors struggling to haul generators out of the garage. However, homeowners like Mike Gingerich of Amesbury, MA have found that it pays to have battery storage at times when there’s neither an electrical wire down, nor a cloud in the sky. On these days, that storage is needed not in their homes, but to back up the grid itself.

Mike is enrolled in the Massachusetts Demand Response program through his utility, National Grid. This allows the utility to draw power from his home backup battery – a Tesla Powerwall – during times of highest demand on the electrical grid. On these hot afternoons in summer when everyone is running their air conditioning at full blast, Mike’s Powerwall becomes part of a grid-tied battery storage network that acts as a supplemental power source to meet increased grid demand.

Solar + Battery to Keep the Power On

“I’m driven to reduce pollution,” says Mike. That was the impetus for his 29-panel solar array and Powerwall, both installed by ReVision in 2018 and 2019, adding to a preexisting 8-panel array from 2006. Most attractive about the Tesla Powerwall and Gateway combination was its ability to bypass the grid, and make use of solar power generated when the grid is down, since grid-tied solar is equipped with automatic shutdown for safety. For Mike, this meant no more having to rig up a kerosene heater to keep pipes from freezing in wintertime outages.

He was alerted to the MA demand response program by his ReVision System Design Specialist, and by Tesla, who is an approved vendor alongside Pika, Sunrun, and SolarEdge. There didn’t seem to be a reason not to sign up. “Instead of my Powerwall just sitting most of the time, I’ll get a lot more use out of it,” says Mike, and he’ll be paid per kilowatt hour for that additional usage. He expects to earn around $700 back after a full year of participation.

Battery Backup is Good for the Grid

Like alternating current, the benefits flow both ways. Drawing power from solar-charged home backup batteries allows the utility to meet energy demand from a clean, local, renewable energy source at the ready. It will minimize need to rely on expensive, highly pollutive peaker plants to make up the difference, and reduce costs overall. In addition, participating utilities National Grid and Eversource, and the state of Massachusetts will gain valuable information to plan for a future grid that must rely more heavily on renewable power sources.

Demand Response at Home

So far, Mike’s home has experienced 5 demand response “events.” They take place at scheduled times in the late afternoon, for a period of 2-3 hours. Apart from the decreasing charge on his Powerwall and tracking information on the Tesla app, the events would otherwise go undetected since they do not disrupt the electricity in his home at all. “If I wasn’t looking at the Powerwall display, I wouldn’t have known it even happened,” says Mike.

The Powerwall, typically fully charged from morning sunshine, will dip from 100% to about 15% charge when there’s been an event, but his battery is programmed with a reserve threshold, so he will never have to worry about an event draining it completely. The other piece of the puzzle, Mike’s rooftop solar array, is also doing its part to squash expenses. “This year it looks like we’re going to produce more energy than we’re going to use,” says Mike. His February electric bill was just 32 cents, and he only sees an electric bill at all from November through February.

With such a drastic offset of expenses and carbon emissions at home, the Demand Response program offers a way to directly share some of those benefits with others in the state. Mike is enthusiastic about the greater effect relying on battery storage for as an energy source will have for people and the planet, the more homes participate. “It’s a relatively small contribution I’m making, but I’m shifting solar output to the time when it’s most needed,” he says. “I like the idea of trying to leave things in a better place than I found them.”

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