Sunday, June 7, 2009

Solar and PG&E (Pacific Gas & Electric)

I've been getting a few questions about my solar and how it all works in regards to the power company. I'll do my best to explain it.

The solar is directly connected to the grid through the inverter. The inverter is designed to not send power into the grid if the electricty is off. This prevents the power company from getting shocked if they shut down their side and want to be sure no solar systems are now powering those lines.

So the way it works here is the power company keeps track of the excess energy you produce during the day. This is done in the simplest terms by letting your meter run backwards. Then at night, lets say, when you're not generating any power your meter runs forward again and you recover that excess energy you created earlier. It's really a great setup since you don't have to worry about costly batteries that need replacing.

Additionally, and to some what complicate what I just said, we have a couple of options here and I went with a time of day (TOD) metering. Peak is 1pm-7pm, partial peak is 7-9pm and 9am-12pm, off peak is 9pm - 9am. This is Monday through Friday. The weekends don't have peaks and all holidays are also like weekends. For peak the energy rates start at about 30 cents per killawatt. Partial peak is about 14.5 cents, and off peak is 8.5 cents. What this means is while I'm at work and not using much energy not only am I making excess energy, but it's not really counted on the kW basis. It's tracked as credits in the form of currency. Later at night when I get home and start using the power again I'm buying it back at a cheaper rate than I sold it for. This helps out the power company to supply their power needs during the "peak" for all users and allows me to only require a system that generates about 75% of my energy use.

It gets more confusing yet...Each Peak, Partial Peak, and Off Peak have their own seperate tiers. Tiers, for those who don't aleady have to deal with this, is an alloted amount of energy you can use at a set price. Once you use more than this the price of the power increases. I believe for my power company their are 5 tiers. So even with the right sized system you might end up going up in tiers during off peak (night time and weekends) simply because you don't generate much here. However, you've also been getting paid quite a bit during peak to cover multiple tier pricing during off peak.

So that's how it all works for me with my power company. Hope this clears things up, I know it confuses me more. :)


Art Wilbur said...

Wow, that is so amazing. I am in awe of what you do and am so jealous!

I'm catching up on the last few posts, but incase they don't cover it, how much time/effort/money did you put into your power setup? I live in FL and would love to do something similar, but fear that I will never have the cash flow to be able to accomplish it.

Brian said...

Thanks Art!

I had the solar installed, so it wasn't any time or effort on my part. It took them a few days to get everything installed. My power company won't let me install the system and be grid tied, otherwise I'm sure there is quite a bit of money to be saved there. The system installed was just over $30k.