Sustainability Science

At first glance, there’s nothing particularly Jetsons-like about Marco Krapels’ 1940s-era home in a prosperous suburb that lies in the shadow of Mount Tamalpais in Marin County, California. Open the garage door, though, and it’s Tomorrowland.

Attached to the wall is a charging station for Krapels’ Tesla Motors Model S electric sports sedan. And next to the charger are two metal boxes that effectively render Pacific Gas & Electric, the 108-year-old utility that serves Northern California, irrelevant. One box channels electricity generated by the SolarCity photovoltaic panels on the house’s roof. The other, a 10-kilowatt Tesla lithium-ion battery pack, can store up to three days’ worth of carbon-free electricity generated by Krapels’ solar array. 

In other words, during the sunniest part of the day, when no one is at home and power demand is low, the Tesla battery pack can store the excess electricity for use in the late afternoon and evening when power prices spike. No dirty and expensive utility electrons needed.  “I should technically be able to function with solar and just the battery indefinitely as long as the sun shines,” says Krapels, a renewable energy financer.

And the cost? Thanks to California incentives that subsidize 60 percent of the cost of energy storage, Krapels is paying less than $40 a month for the battery pack as part of a lease deal with SolarCity, the Silicon Valley company that installed the solar battery system.