Together, furnaces and water heaters account for a third of all emissions that come from the world’s buildings. And unlike lights and A/C units, most of them run on fossil fuels, not electricity. (Whether you use natural gas, heating oil, or propane depends largely on where you live.) This means we can’t decarbonize hot water and air simply by cleaning up our electric grid. We need to get heat from something other than oil and gas.
