I was amazed to find in my September 2012 SCE bill their Power Content Label for 2011, a report on their energy sources required by California law. When I tried to look up more information on the California website, all I found was the old 2010 power content labels for California utilities. So SCE consumers got it hot off the press. I feel honored, and will analyze it here for its Greenhouse Gas (GHG) emissions. After further reflection, since they undoubtedly had to pay for the power close to the time it was provided, why did it take them until September to add up the numbers? On the other hand, how many consumers were anxious to analyze it as I am going to do below? They also included the 2011 California power mix, which I will also analyze below.
For CO2 emissions we take average values at 33% efficiency of power plants, giving for coal 2080 pounds of CO2 for 1000 kWh, and for natural gas, about half of that or 1170 pounds of CO2 for 1000 kWh. Since even the lifetime emissions of renewables, large hydro, and nuclear are very small by comparison, we approximate them at zero and call them GHG free.
For the 2011 California power mix, we have zero GHG for renewables at 14%, for large hydro at 13%, and for nuclear at 16%. This gives a total of 43% of California power is generated GHG free. The GHG comes from coal at 8% or 2080 pounds of CO2 x 0.08 = 166 pounds per 1000 kWh, and from natural gas at 37% or 1170 pounds of CO2 x .37 = 433 pounds of CO2 per 1000 kWh. The sum of these is 599 pounds of CO2 per 1000 kWh, which is about half that of natural gas alone for the total.
Something is missing, however, and that is 12% of “unspecified sources of power”. If the unspecified source is coal, it adds 2080 x .12 = 250 pounds of CO2 per 1000 kWh, or 42% of the total. If the unspecified source is natural gas, it adds 1170 x .12 = 140 pounds of CO2 per 1000 kWh. Since the unknown sources can be such a large amount of the total, up to 42%, it is a major failure of the state requirement as it currently exists. Clearly the providers of the unspecified sources know who they are paying for the power per kWh, and with modern computers could keep track of how much they pay each year to each source. Even if only a statewide average is available, it would help clarify the accounting. With some probabilities of sources and utilities, a fair estimate of the sources to each utility could also be obtained.
Now we turn to the power mix to SC Edison. They used GHG free 19% from renewables, 7% from large hydro, and 24% from nuclear, giving a total of 50% of their power being GHG free. Coal at 8% contributes 2080 x .08 = 166 pounds CO2, and natural gas at 27%contributes 1170 x .27 = 316 pounds of CO2, for a total of 482 pounds of CO2 per kWh. The unspecified sources at 15% would add 312 pounds of CO2 for coal, and 176 pounds of CO2 if natural gas. The coal would add 65% to the total, again a dramatic argument for defining the sources of the unspecified power sellers.
