CAISO's own documents quote battery capacity in MW. So I don't think you can just blame journalists.
reply"Battery storage capacity grew from about 500 MW in 2020 to 13,000 MW in December 2024"
https://www.caiso.com/documents/2024-special-report-on-batte...
As another commenter notes, utilities are interested in "capacity on call" i.e. instant power generation.
I struggle to understand why journalists consistently failed to use Wh as a unit of power. People generally can understand it because it is how they are billed and how appliances are rated.
replyEven on HN people will defend not using Wh because there is some grid or city in the USA that bills differently.
Battery storage is always measured in the amount of power that can be delivered (Watts). Secondarily it’s measured in the number of hours that power can be delivered (hours, which is almost always about 4.) To get MWh you multiply watts times hours. This is standard in the industry and has nothing to do with reporters.
replyBecause American literacy in math and hard sciences has only declined over the decades since the post-Sputnik spurt that benefited my generation. Journalism as practiced today doesn't require scientific literacy or rigor, or at least, they are secondary to the purposes of the writers' employers.
replyLater, they say “lithium ion batteries only have 4 to 6 hours of capacity”, which again, what? But maybe that implies that the actual capacity rating is their “capacity” x 4-6.
replyUh... "Wh" is not a unit of power. Watts are units of power. Watt-hours measure energy. Probably journalists are getting this wrong for the same reason you are.
replyThe commenter was right that the correct unit is Wh, then slipped up. Does gasoline contain power? Do "high-power" Li-ion batteries? In common parlance, power and energy are used interchangeably. I believe people writing about science should hold themselves to a higher standard, but there is always something more important.
replyI do not know why this particular one gets engineers so annoyed. Energy and power are synonymous in conversation with normal people. There is very little real world scenarios where people would be exposed to the precise meanings -of course everyone gets it wrong.
replyBut the premise of the comment I was replying to was exasperation that journalists got it wrong!
replyNo, you were right on the money. Just idly thinking out loud why this is even an issue. Muggles get technical details wrong all the time. Yet any article about energy is going to get a few people riled up when the units are wrong.
replyUtilities are used using MW when discussing supply and demand. Because balancing that is critical. So power is what they care about when discussing grid connections.
replyThe billing side and customers are concerned with total energy. So kwh.
Journalists typically don't know the difference. Which is why they list storage capacity in watts. They don't know any better and they don't care.
Far as I can tell multiply the watts by 4 hours to get watt hours.