New photovoltaic users in California look forward to their first “trueup” bill from PG&E, as its 12 pages are dense with tables and graphs showing energy usage and fees for the month. It promises to reveal in fascinating detail the PV system’s production and the household’s demand, culminating in the month’s balance — charge or credit — which ultimately, at the end of the year, will ideally be $0 for a well-sized PV array.
But a month later, photovoltaic users simply file the monthly trueup bill without a glance, because 11 of those 12 pages are utterly incomprehensible.
I used to read the cover page, because as noted above it shows the running total dollar amount, which is both interesting and easily understood. Most of the time.
My numbers for the first quarter:
|Month||Current unbilled charges||Total unbilled charges|
In other words, according to the trueup bill, in February we generated about 30,000 kWh of surplus power, which if my math is right would actually require 500 days of pure sunshine, with no clouds, and 70°F ambient temperatures so the panels don’t get too hot. Oh, and those would have to be 24-hour days. And the sun would have to be perfectly overhead the entire time.
Considering that we get somewhat less than 24 hours of perfect direct sunshine every day, and we occasionally see a cloud, it would actually take more than 500 days to generate 30,000 kWh of power. Our array was turned up in January, 2004, and to date we’ve only generated about 9850 kWh… so we’ll need something like 7.7 years to hit 30,000 kWh. A bit more than 28 days, anyway.
Then in March, according to the trueup bill, we burned over 30,000 kWh, which I guess would be possible if I accidentally left the oven on for, say, 8 months. In February.
So the dumb thing is that there’s no bounds checking in PG&E’s bill calculation. It ought to seem unlikely that a household could spike its solar electric generation by a factor of 100 within a month’s time, especially considering that the last time a private citizen tried to put a 30kW PV system on the grid, it took 14 months of negotiations and a lawsuit before PG&E turned it up.
The other dumb thing is that the correction one month later was also incorrect. My unbilled charges for March should be $100 or less, not $544. But nobody caught this either. Had I not called to complain, I’m sure my year-end bill would have been ~$400 too high.
Fortunately, PG&E was relatively quick with the explanation (a mis-read meter) and a corrected trueup bill.
Unfortunately, our generation for 2006 is low by about 12% as compared to 2005. I’ve contacted our vendor to investigate possible problems. It’s possible the weather this year is to blame; our vendor can compare our generation to other installations in the area.
See also our running total electric charges for the year — we appear to have recently squandered a savings of ~20% off our 2005 fees. This week’s heat wave sure isn’t helping anything, either.