Energy efficiency improvements lower the overall energy demand of various products and processes. The next piece of the puzzle is reducing the dependence on fossil fuels to meet energy demands. Large amounts of fossil fuels are currently being used for various purposes such as heating and cooling of homes and businesses, for manufacturing and production of steel, chemicals, and cement, and for most modes of transportation. A successful economy-wide decarbonization relies on end-use sectors (i.e. buildings, industry, and transportation), being modified to run on renewable power and heat. In most cases this will require those sectors to transition en masse to meeting energy demands not through the direct combustion of fossil fuels, but through electrification or alternative low-carbon fuels.