Friday, February 16, 2018

Suburban 5-4-and-a-Door Solar: How Much Does Power Really Cost?

As we enter month seven of our solar panel installation, we've been doing some intensive numerical analysis to find out exactly how much we are saving. One of the problems that we encountered was determining exactly how much we were really paying for power.

Georgia Power publishes their official rates in cents per kWh based on the month of the year and the amount of power used. Theoretically, the numbers in the table below should add up to the "Service" line on the bill, but we discovered that they don't.

Month
less than 650kW
650 to 1000kW
more than 1000kW
October - May
5.6582
4.8533
4.7641
June - September
5.6582
9.3983
9.7273

After a few calls with Georgia Power, we discovered that there is an additional "fuel charge" included in the Service line. The fuel charge can change at any time, but is currently a $10 base charge plus 2.696 cents per kWh. Why these numbers are not included anywhere on any document that is published by Georgia Power is hard to understand.

In addition to service rates, there are per kWh charges for Nuclear Regulatory Fee, Environmental Fees, and Franchise Fees. The rates for these are also not published, so we did some linear analysis to figure out how to calculate them for arbitrary kWh. The equations below are almost certainly not correct, but they give numbers that are close for kWh values we've seen so far.

Nuclear Fee (dollars) = 0.009461*kWh-1.703
Environmental Fee (dollars) = 0.01243*kWh-2.269
Franchise Fee (dollars) = 0.00444*kWh-0.5845

And, of course, there is the 7% sales tax. All of this adds up to a cost of power between 10 and 16 cents per kWh. The graph below is what we have actually paid for power per kWh over the last few years.


Compare that to the 3.5 cents / kWh that Georgia Power pays to homeowners for generated power and the popularity of local storage options like the Tesla battery are easy to understand. Why sell power to the utility at 3.5 cents only to buy it back later at 16 cents? It also explains why net metering (which is available in some states and requires the utility to only charge for the net power used) is very popular with customers and not so popular with utilities.

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