Thread by @jglarusso

1/ .@isonewengland’s July 17 Newswire contains some insights regarding the performance of behind-the-meter (BTM) PV in its service territory during the recent 6/29-7/5 heatwave. bit.ly/2NurOd0

2/ The hour of highest demand (24,180 MW) occurred 7/5 between 5-6 p.m. Indeed, all of the daily peaks during the heatwave came in the late afternoon/early evening, between 4-7 p.m.

3/ Per the Newswire “[BTM PV generation] peaked each day at around 2 p.m. during the heat wave, providing approximately 2,000 MW [(i.e. 2 GW)] to homes and businesses with solar arrays.”

4/ ISO-NE Dir. of System Ops., John Norden, summarized the effect of that 2 GW of BTM PV: “Solar contributes to the reduction in the peak load and also contributes to moving the peak [demand] that we see here at ISO New England to that 5 to 6 p.m. timeframe.”

5/ In short, BTM PV reduces peak demand on the grid AND makes the hour of peak demand later. Because temperatures begin to cool as the evening progresses, this means that more expensive and dirtier peaker plants have to be run for fewer hours, avoiding fossil fuel emissions.

6/ This is exactly what happened during the 6/29-7/5 heatwave. Per ISO-NE: “[w]ith demand evading high levels, ISO New England had to call only minimally on older coal and oil resources.”

7/ Q: So what percentage of daily summertime demand is being met by those thousands of humble BTM PV arrays on the roofs of New England’s homes and businesses?

A: Quite a lot!

Let’s take yesterday, 7/19, for example. It was a beautiful, cloudless day ...

8/ As you can see, shortly before 2 p.m. yesterday (when solar generation would have been at its maximum) the demand being served by ISO -NE equaled 15,837 MW. Adding in the 2 GW of BTM PV generation, the region’s entire demand equaled approximately 17,800 MW.

9/ So at 1:52 p.m. yesterday BTM PV generation was meeting more than 11% of ISO-NE system demand. The second largest source of zero emissions power after nuclear! Moreover, due to BTM PV’s contribution, almost ½ of system demand was then being met by zero emission resources.

10/ (Remember when looking at the at the 7/19 1:52 p.m. resource mix that the “renewables” category includes refuse, wood, landfill gas, and methane, in addition to wind and in-front-of-the-meter solar, and that only about 2/5 of those “renewables” are zero emission resources.)

11/ Q: So where is all of that glorious BMT PV on the NE grid?

A: ISO-NE has a map showing exactly where it is ...

(Rhetorical Q: Think state policies supporting solar matter much?)

12/ So, what are some implications regarding the quantity and siting of BTM PV? Well, you’ve probably heard the argument that BTM PV owners are free-riders: they pay no electric bill, yet they still depend on the grid when the sun goes down and they pay nothing to maintain it.

13/ Worse still, so the argument goes, as more and more people get BTM PV, their poorer neighbors who can’t afford it pay increasing amounts to maintain the grid that their wealthier BTM PV-owning neighbors still depend on.

14/ ... It is a class warfare argument—the rich are enriching themselves still more at the expense of their poorer neighbors, and the poorer neighbors aren’t benefiting at all from the BTM PV. This is the argument made by those champions of the little guy ...

15/ ... the local distribution companies (yes, electric utilities). The argument is made to justify imposing surcharges or minimum bills onto those, supposedly, free-riding BTM PV owners.

But ISO-NE BTM PV data suggests how much BTM PV is saving *all* NE electric customers.

16/ First, as we’ve seen (4/ & 5/🔝) BTM PV reduces peak demand on the grid and makes the hour of peak demand later. This reduces the number of hours that dirtier and more expensive peaker plants must run. The result? Lower-cost electricity for all NE electric customers.

17/ Second, in the absence of the 2 GW of BTM 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.

18/ When MGS units 8 & 9 were built in 1999-03 (combined nameplate capacity 1414 MW) they cost $1.3B. So how much would it cost to build 2,000 MW of gas generation today? Billions. That is another avoided cost benefiting NE electric customers, exclusive of FF externalities.

19/ And then there is also the avoided cost of all of the transmission and distribution infrastructure—wires—that would have otherwise had to be built—still more savings for all NE ratepayers.

20/ It’s also clear that by avoiding the construction of GWs of natgas generation, BTM PV is playing a part in diminishing the need for new natural gas pipelines. And with the cost of battery storage declining, the chief criticism of solar—its variability—will be addressed.

21/ If you’d asked me what percentage of regional electric demand was being met by BTM PV on clear, NE summer afternoons *before* I’d read the 7/17 Newswire, I’d have said 3-4%, and been convinced I was overestimating. I would have had no idea it could approach 10% or more.

22/ The point is this: it’s a clear & irrefutable fact that BTM PV has arrived; that *all* NE electric customers benefit from it; & that its positive effects on the ISO-NE grid will only grow as battery storage becomes ubiquitous and the amount of installed BTM PV increases. ###