America must shift away from fossil fuels and towards clean, renewable sources of energy in order to protect our air, water and land, and to avoid the worst consequences of global warming. Renewable energy sources, such as wind and solar power, are virtually unlimited and produce little to no pollution. With renewable energy technology improving and costs plummeting, it is now possible to imagine a future in which all of America’s energy comes from clean, renewable sources. The availability of wind and solar power, however, varies by the hour, day and season. To repower our economy with clean energy, we need an electric grid that is capable of incorporating large volumes of variable renewable resources. Energy storage technologies can be an important part of that electric grid of the future, helping to assure reliable access to electricity while supporting America’s transition to 100 percent renewable energy. To get the most benefit out of energy storage, however, policy-makers and the general public need to understand how energy storage works, where and when it is necessary, and how to structure public policy to support the appropriate introduction of energy storage.