A battery large enough to power the U.S. would be the size of 2,200 Walmart SuperCenters
The U.S. uses about 500 gigawatts of power at any moment. Is it possible to cover that whole demand with emissions-free power sources? Well, nuclear, which has virtually no greenhouse gas emissions, could account for about 20 percent; the rest would have to be renewables. And renewables are intermittent, so they’d have to be backed up by about 80 gigawatts worth of batteries, says Davide Castelvecchi at Scientific American.
To put that in perspective, that’s the equivalent of the simultaneous output of 80 nuclear power plants (or 80 sizable coal-fired power plants).
The largest battery complex built to date, in China, stores about 36 megawatt-hours of energy. So assuming you need at least an hour of backup in your battery system, you’d only have to build about 2,222 copies of the world’s largest battery complex to accomplish your goal.
Here’s what the one in China, which is as big as a Walmart SuperCenter, looks like:
How Big a Battery Would It Take to Power All of the U.S.?, Scientific American.