In Stockholm, the heat pouring off the city's data centres is no longer wasted but piped into the district heating network, enough to warm around 30,000 apartments a year, which means the warmth thrown off by people streaming films and storing photos now quietly heats thousands of homes across the city.

In Stockholm, the heat pouring off the city's data centres is no longer wasted but piped into the district heating network, enough to warm around 30,000 apartments a year, which means the warmth thrown off by people streaming films and storing photos now quietly heats thousands of homes across the city.

Stockholm found a way to stop wasting the enormous heat generated by data centres—and turned a climate problem into a solution for thousands of cold apartments.