By Paul Hockenog for Wired
Stefan Paris is a 55-year-old radiologist living in Berlin’s outer suburbs. He, his partner, and their three-year-old daughter share a snug, two-story house with a pool. The Parises, who are expecting a second child, are neither wealthy nor environmental firebrands. Yet the couple opted to spend $36,000 for a home solar systemconsisting of 26 solar panels, freshly installed on the roof this month, and a smart battery—about the size of a small refrigerator—parked in the cellar.
On sunny days, the photovoltaic panels supply all of the Paris household’s electricity needs and charge their hybrid car’s electric battery too. Once these basics are covered, the rooftop-generated power feeds into the stationary battery until it’s full—primed for nighttime energy demand and cloudy days. Then, when the battery is topped off, the unit’s digital control system automatically redirects any excess energy into Berlin’s power grid, for which the Parises will be compensated by the local grid operator.
“They convinced me it would pay off in 10 years,” explains Paris, referring to Enerix, a Bavaria-based retailer offering solar systems and installation services. “After that, most of our electricity won’t cost us anything.” The investment, he says, is a hedge against rising energy costs. Moreover, the unit’s smart software enables the Parises to monitor the production, consumption, and storage of electricity, as well as track in real time the feed-in of power to the grid.
The Parises are one of more than 120,000 German households and small-business owners—and an estimated 1 million people worldwide—who have dug deep into their pockets to invest in solar units with battery storage since lower-cost systems appeared on the market five years ago.