Wednesday, March 28, 2012

First bill

I received my first PG&E bill since installing the solar this week. Unfortunately, PG&E assumes when you go to solar, you don't want to do any analysis, so they send you a simplified bill. The bill didn't have the details I was looking for in order to see what my savings are. I called up the solar customer service at PG&E (the normal customer service is no longer able to help me) and found that the information I wanted was on page 4 of the bill, and they normal only send pages 1 and 2. They were able to flag my account to receive the detail bill from now on though.

Now that I have the full bill, I am able to see that I used 1389 KWh of power from PG&E for the 27 days that the bill covered. My solar system generated just over 547 KWh of power for the same period, putting total usage at 1936 KWh. Unfortunately, on March 1, PG&E changed rates further complicating the cost analysis, but with some help from Excel, I was able to do some calculations.

First, the big positive is that I stayed in the Tier 3 pricing, using less than 200% of baseline. This kept me from paying for the highest cost power. Without the solar, I would have been well into Tier 4 pricing. Each KWh in Tier 4 is 4 cents more than in Tier 3 (and Tier 3 is more than double Tier 2 pricing, adding 15 cents per KWh to the price). In order to calculate my savings, I added the solar generation to the appropriate tiers. My Tier 4 usage alone would have cost ~$128, but solar was able to completely eliminate that. I was able to reduce Tier 3 usage by another ~$45, putting the total savings for the month at $173.

These numbers are approximate, since I am unable to figure out how much of the power I used from solar was used during the partial peak prices (1-7pm weekdays) vs off-peak (all other times). PG&E allocates baselines based on % of power used at each of the rate periods (I used about 10% of my power during the partial peak period, so my baseline quantity for partial peak pricing was 2.86 KWh a day, rather than the 7 KWh a day it would have been had they done it based on % of the day spent in each rate category). Therefore, I made the assumption that all of the solar would have been used during the more expensive Partial Peak time-frame, rather than the cheaper off peak. This means my saving estimate is probably a little high, but the best I could do.

I did run the numbers, and found that the way PG&E does the allocation of the baseline actually works out in my favor this month, since I would not have used enough power to hit the full Tier 2 limits had the allocation been done on a percentage of time basis, so I would have had more Tier 3 usage in off-peak. The savings was right around $5.

Bottom line, the solar system saved me from paying PG&E around $173 this month, and cost my $0, since my first year of solar power is free. If I was paying for the solar power, it would have cost around $120, putting my net savings this month at $53.

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