By Andrew Evers, CNBC • Updated 2 hours ago Andrew Evers | CNBC Tesla CEO Elon Musk announced in 2015 that the electric-vehicle company would be getting into the energy business. Now, it's starting to take off. On its Q4 2020 earnings call, the company said its battery deployments increased 83% in 2020, particularly thanks to the popularity of the Megapack, which stores energy for utilities. Renewable energy such as solar and wind need battery storage for when the wind isn't blowing and the sun isn't shining. As nations around the world set goals to transition to renewables, demand for these large-scale storage systems is on the rise. Grid-scale battery storage is expected to become a $15 billion market by 2027, according to Grand View Research.