The New England power grid did quite well during the week-long heat wave in early July – there was no strain on moving power around, thanks to the gazillion dollars worth of upgrades that have been built in the past few years, and no strain on power supply, and for most of the period the real-time wholesale cost of electricity stayed in the normal range.

At least some of the reason for that success is the growth of “behind the meter” solar power, which means photovoltaic panels, often on roofs. These don’t feed electricity directly into the grid like a traditional power plant that ISO-New England (the folks that run the grid) can easily see. Most of their impact involves reducing customers’ need to pull power from the grid, which is an effect that grid operators can see only indirectly, mostly by extrapolating likely reduction in demand due to the weather. That makes it a little harder to parse how much good it does, or doesn’t, do.

I’ve seen some discussion about this fact, but I particularly like one that came in the form of a Twitter feed. (If you’re not a Twitter user that will sound goofy, but it just means that each paragraph of the discussion stands along in a series of linked posts.) It’s from a guy named Joe LaRusso, the Energy Efficiency and Distributed Resources Finance Manager for the city of Boston. You can read it here – I’m not sure whether you need to have a Twitter account of your own to see it.

His says that all the behind-the-meter solar which has been built, mostly in Massachusetts in Connecticut because they’ve supported it, provided as much as 11 percent of New England’s total electricity needs during peak usage of the heat wave. That’s part of reason why we didn’t have to turn on more coal- and oil-fired plants to tide us over while all those air conditioners were cranking. The solar also shifted the peak demand from the grid, moving it from the historical period of around 2 p.m. each day, to more like 4 or 5 p.m. That helps reduce strain on the grid because the day is starting to cool off naturally by 4 p.m.

He argues that this is why the “your solar panel is costing me money” argument isn’t real, because rooftop solar means utilities and the grid can avoid costs that would have been picked up by other ratepayers. “In the absence of the 2 GW of behind-the-meter PV, 2 GW of generation—likely gas generation—would have to be built. How much would that cost? The recently much-written-about Mystic Generating Station (MGS) provides us with some idea. …  Billions. That is another avoided cost benefiting NE electric customers.”

It’s an interesting discussion that will be going on for a long time.




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