ISO-New England, the folks who run the six-state power grid, estimate that there are 4,000 MW of “behind-the-meter” solar (i.e., rooftop, although some of that is ground-mounted) in the region. That’s a little more than three times the output of Seabrook Station nuke plant, although of course solar is intermittent so Seabrook’s annual production is much more.
They’ve added a tweak to their online system-watching tool, showing real-time estimated BTM solar. Right now (a sunny Wednesday at 3 p.m.) it makes a big difference. Here’s the chart without BTM – yellow is total production, blue is forecast:
… and here it is with BTM:
By the way, if you fiddle with the tool you’ll see there’s a setting called “Pump Load” – that, I found out after asking, is the amount of energy used to pump water uphill as part of the pumped-hydro storage system. It’s “charging the battery”, if you will.