In Mint Plaza, mere steps from the flagship Blue Bottle Coffee Shop, one of the world's hippest, there's a vestige of the city's industrial past. Marked by two large smokestacks, a set of boilers power a steam system that provides heat for 170 buildings totaling 37 million square feet of space. Fuel is burned here to create steam that's piped all around downtown San Francisco.
The distribution system has remained nearly identical since the map below was drawn in 1917, except that one new line runs to the Westfield mall at 5th and Market.
Heat distribution networks like this are called district heating systems. Most old cities have pipes embedded in them that can carry this kind of energy, a gift from our ancestors, who prized infrastructure.
They're an old, hidden network far less prominent than the water pipes, electricity lines, and Internet cables that power a modern city. But they're still used and useful.
There's even an energy bonus to them: they tend to be more efficient than on-site heaters, especially if the facilities make both heat and electricity. Those plants go under the label "combined heat and power," or CHP, and they've been growing rapidly over the past decade.