Monday, May 1, 2023

Another Solar Update: The Day We've Been Waiting For

We received our latest power bill from Central Hudson and the day we've been aiming for has finally arrived: We owe nothing for electrical power beyond a flat service fee of $35.10 plus state and local taxes of 83 cents. That's it. 

It shouldn't come as a surprise, and yet it still does. Every few days I take a picture of our meter and pretty much every time since the start of 2023, the number indicating our overall consumption is lower than before. But to see this confirmed on a bill after 10 months with the system in service is terrific validation of the plan we envisioned when we first decided to go solar. 

Here's how the usage graphic appears on the bill, and of course it's not perfect — that "estimate" for August is especially problematic because I know it's wrong. I know from my own data that in the first quarter of the year, net production was more than 113 percent of consumption. And I'm not sure why the bill doesn't display a zero for that period as well. We send photographs of our actual meter readings to the billing office, and I save them. So I can prove that on Jan. 1 the meter read 2104 and that on April 1 it read 1826. So the math shows my net consumption for that period a negative 278 kWh. How the utility arrived at that figure of net consumption of 177 is unclear except that it may have to do with the days on which we submitted our readings. Meter submission days make a difference. I've created a new view in the SolarEdge tracking app to show us detailed production between precise billing dates — the current period ends on June 26 — we'll have a clearer picture of the utility's math. 

Meanwhile, the net consumption figures for the year so far continues to look better every day. (See chart.) As of today net production is 2.85 mWh against consumption of 2.29 mWh or 124 percent. That includes 1.93 mWh of exported power and 0.92 mWh consumed directly from solar. That means the panels directly supplied about 40 percent of our daytime power needs. 

Continuing the trend about which I wrote earlier, the sunny and cold days of February continued through much of March and the first half of April. March turned out to be sunnier and more productive month than April. 

But there's still some big questions lying ahead as we move from spring into summer. The big item: The pool will open in about two weeks and that will bring with it the high power consumption of the electric pool heater. 

Also in June: The system's anniversary date, which is when the utility supposedly credits us for the net billing effect of all the excess power that has been "exported" to its grid. Since the system only operated for about half of last year, we ended 2022 with production-to-consumption ratio of about 80 percent, ie, we consumed more than we produced. My math — and I may be doing it wrong — shows that given last year's abbreviated production and high consumption, has us running behind by more than 2 mWh. So even though we're ahead for calendar 2023 so far, we haven't yet produced more power overall than we've taken from the grid since the beginning.

Here's the math: 

2022 net grid consumption after solar consumption and export: 3.17 mWh
2023 net grid consumption, after exports so far: (1.12) mWh
Difference: 2.05 mWh

In order to build up that summer billing cushion I had been hoping for — the utility calls it a "generation bank" — we have to produce more than 2 full megawatt hours above our consumption by the middle of June. That's a lot. This will of course be an easier exercise next year assuming a repeat of a sunny fall and winter. It also means getting control of consumption during the summer which will be a challenge. I'm contemplating a thermal blanket for the pool to preserve the water's heat and minimize the need for running the heater. For now, here's hoping for some really sunny days in May and June. 

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