This story was originally published by Yale Environment 360 and is reproduced here as part of the Climate Desk collaboration.

Yet the couple opted to spend $36,000 for a home solar system consisting 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.

“They convinced me it would pay off in ten years,” explains Paris, referring to Enerix, a Bavaria-based retailer offering solar systems and installation services.

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.

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