"Tech companies confront an inconvenient fact," writes Mills. "The global cloud uses more energy than is produced by all the planet's wind and solar farms combined." In fact, digital traffic has become the fastest-growing source of energy use. While nearly every tech company has pledged to transition to renewable energy sources, most data centers are physically connected to the conventional power grid, fueled by hydrocarbons. The modern economy won't be exclusively powered by renewables any time soon.