Hidden Gauge of U.K.’s Zero-Carbon Drive Sits in Your Cellar

Tired of the crowds and air pollution in London, Amy Willis bought an 18th century house in a Suffolk village two and a half hours away from the city and immediately started renovations. Two years later, she’s stuck on modernizing the heating system—and so is, in some sense, climate progress for the entire U.K.

Her home isn’t connected to the gas grid, so Willis relies on trucks to deliver gallons of oil that fill a boiler. The process is expensive, and Willis doesn’t like that she’s among the millions of British households contributing to global warming by burning fossil fuels to keep warm. She ...