Marin Clean Energy and Solar Part 2

Following up on my previous Marin Clean Energy blog topic, I did some delving into the PG&E side of the bill.  I have an example that will help us here from an actual MCE customer and solar power producer, let’s call him Customer A.  Let’s look at the MCE portion of the bill first for the month of July.   He was able to generate an excess of 170 kWh of electricity during the On Peak period between 12pm and 6pm, which he sold back to MCE at $.38 per kWh (MCE actually pays the retail rate PLUS a penny!), producing a credit of $64.60.  During the Off Peak period when his solar system wasn’t producing, he consumed 660 kWh at a rate of only $.05 per kWh, so the cost was only $33.  So, factoring in a small surcharge of $.14 also, we add the On Peak and Off peak figures to get to a credit, or profit, of $31.46 for Customer A for the month of July.  Nice numbers right?

Ah, but now we must also analyze the PG&E portion of the bill which accounts for transmission & distribution.  PG&E also handles the billing for both MCE and PG&E.  Let’s go back to Customer A’s bill.  His charge for the PG&E portion came to $43.74 and it accounts for the kWh he produced and also what he consumed.  So he generated 170 during On Peak and consumed 660 during Off Peak, producing the Net figure of 490 kWh.  I spoke with a PG&E representative for a long while to try to breakdown the actual costs per kWh that go into that $43.74 charge.  In a nutshell, it couldn’t be done.  The word “complex” was used liberally, and it came out also that the E-7 Time of Use rate plan will no longer be offered to MCE customers!  Since the representative couldn’t provide the detail on the rates, I just did a simple calculation using the 490 kWh and the $43.74 charge, which yields an overall rate of $.09 per kWh.  So, for Customer A, who is lucky to be “grandfathered” into the E-7 plan, his net charges for both MCE & PG&E come to $12.28.  With that laborious task now complete, let’s move on to another MCE customer.

The customer, Bob, happens to have an older meter which actually spins backwards.  Pretty cool I must say.  Also, Bob looked at his prior usage data for this time of year and calculated he consumed about 23 kWh per day.  Yesterday at about 4pm, he looked at his inverter which read that his system had produced 25 kWh so far that day.  So, he’d already produced beyond what he’d normally consume and still had a couple of hours of sun left.  Good stuff.  Now let’s look into Bob’s history a bit as it pertains to solar and energy efficiency.

Bob is an architect by trade and he designed the structure on which the solar system rests.  He also designed and built his home in Marin in 1978, which was constructed with passive solar heating and solar thermal water heating.  The home also uses a passive heat collector in the form of 17 tons of rock beneath the foundation.  As the home heats up during the day, the warm air rises to the ceiling.  There it is sucked into a vent and funneled down to the rocks below.  The rocks absorb the heat during the day and act as a heat source at night.  Bob also helped design one of the first solar structures for the Forest Service in the 70’s.

The structure was a lookout tower on Antelope Peak in Lassen National Forest.  The solar system designed for it used 8 panels which had peak output of only 294 W.  The PV cells had to be specially made by NASA Lewis as there were no panels on the market back then.  They also built a backup storage system consisting of 18 deep cycle batteries.  The beauty of solar for the Forest Service was that it required very little maintenance.  Gas generators were dirty, noisy and they happened to break down a lot.  The problem was that solar was in its infancy and come the 1980s it was basically put to a halt.

And this is why more than 30 years later Bob has finally installed his solar system at his home in Marin!  He has been waiting for this day for a long while, and now both the technology and the economics make great sense.  More to come on Bob’s solar system as we collect more production data…

Jason Moshonas is an Energy Consultant at Heliopower.
He lives and blogs in Marin County California
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