is a correspondent at Vox writing about climate change, energy policy, and science. He is also a regular contributor to the radio program Science Friday. Prior to Vox, he was a reporter for ClimateWire at E&E News.

The tricky thing about generating electricity is that for the most part, you pretty much have to use it or lose it.

This fundamental fact has governed and constrained the development of the world's largest machine: the $2 trillion US power grid. Massive generators send electrons along a continent-wide network of conductors, transformers, cables, and wires into millions of homes and businesses, delicately balancing supply and demand so that every light switch, computer, television, stove, and charging cable will turn on 99.95 percent of the time.

Making sure there are always enough generators spooled up to send electricity to every single power outlet in the country requires precise coordination. And while the amount of electricity actually used can swing drastically throughout the day and year, the grid is built to meet the brief periods of peak demand, like the hot summer days when air conditioning use can double average electricity consumption. Imagine building a 30-lane highway to make sure no driver ever has to tap their brakes. That's effectively what those who design and run the grid have had to do.

But what if you could just hold onto electricity for a bit and save it for later? You wouldn't have to overbuild the grid or spend so much effort keeping power generation in equilibrium with users. You could smooth over the drawbacks of intermittent power sources that don't emit carbon dioxide, like wind and solar. You could have easy local backup power in emergencies when transmission lines are damaged. You may not even need a giant, centralized power grid at all.

That's the promise of grid-scale energy storage. And while the US has actually been using a crude form of energy storage called pumped hydroelectric power storage for decades, the…

Umair Irfan

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