Don't stop reading there! The next three words are "on the nation's grids" (at least in the first occurrence of the phrase). When dealing with grids, capacity always refers to power measurements.

The journalists did not mess up anything, they are actually using the correct units used by people who run grids, build grid assets, plan grids, etc. The only people who are confused are those who don't know about grids, but know a few things about electricity in other contexts.