One year of solar

And the tale of how PG&E ends up the big winner

Jun 25, 2014

Last year around this time, I posted about the theoretical financials for installing solar panels on my house as well as some real data from the first month of the system live. It's been a year now, and I have solid data about what our system looks like for an entire year.

Net Grid Usage

12 month power bill.

Here's a scan from my latest PG&E true-up bill showing the last 12 months of power usage / charges. As you can see, in the winter months I was using more power than I was generating and was paying $10/month or so for the power that my panels couldn't provide. However, in the middle of the summer I was generating enough power to end up with a $30-$40 credit each month. After one year, I had accumulated $100 of power credits*! This is much better than my estimates of the panels covering about 85% of my power costs during the year.


While PG&E can only tell me net power, SunPower gives me data on how much power I actually produced.

12 month solar generation.

Our estimate was around 4,830 kWh / yr, but we actually produced 5,806 kWh (20.2% higher).

Why did we produce more? My guess would be the dry year we've had in CA, leading to a statewide drought. Fewer rainclouds equal more sunlight.

PG&E Credit (*)

So, did PG&E cut us a check for $104.74? Unfortunately No.

The accounting you see in the first image pays me retail rates for the power I generate. My generated power gets sold to my neighbor by PG&E at say 12c/kWh, and PG&E then pays me 12c/kWh for that power (hand waving as their is tiering involved).

However, this accounting is only used to determine a credit that can be used against charges later in the same year. In order to be paid, PG&E re-does all of the accounting. They start over, charging me retail rate for the power I buy, but paying me wholesale rate (4c/kWh I think) for the power I sell them. Under this setup, I'd end up having to generate 2-4x what I use in order to break even. I'm nowhere close to that, so the "cut Gregable a check" accounting is zeroed out.

On top of this, even though my monthly bill is $0 and PG&E is profiting from the power I put on their grid, PG&E now charges me $5/month minimum for being connected to that grid. Thus, I still paid PG&E about ~$60 last year for electricity rather than PG&E paying me ~$100. I buy natural gas from PG&E too, but the power credits don't get to count against those charges either.

I'm happy with the results of my install, and knew all of this up front, but still feel like this sets up bad economic incentives. This particular setup means that someone installing solar really wins the most if they install less than the amount they will need, since over-generating results in benefiting only the power company. Even if my roof is a better spot for panels than my neighbor's, the incentive is for me to put less panels on my roof and them to put some more on theirs, rather than the more efficient distribution.

Right now, power companies seem to be trying to fight solar by adding minimum monthly charges and getting permission to pay less than retail rates for the power they buy. This is even after the fact that the solar production is often at times when PG&E pays more for power wholesale than they charge retail. I personally think power companies should be able to charge some type of distribution cost to solar users for generated power, but they should continue to buy the power at (discounted) retail rates even to the point of cutting the solar user a check. Allowing the power companies to have both advantages has an effect of subsidizing fossil-fuel power generation at the cost of solar customers.