Paul, David, all, thanks for
Paul, David, all, thanks for commenting and making the story more in depth.
I feel I should explain my $0.30 to $0.40 cents a gallon equivalent comment for clarity.
My overall system size is 7.5kw and that system powers both our home and car. It is a balanced energy use and energy generation solution, We generate 11,700KWH a year and we use 11,700KWH per year, about 3700kwh for the Mini-E and 8000kwh for the home.
Each KW of a solar PV system cost today approximately $3700 when part of an average sized residential system. I think the main difference in Paul and my calculations are that my system installed in two parts, 5 years ago, and 2.5 years ago was cheaper per KWH.
Electric cars such as the Mini-E are returning between 3.5 and 4.25 miles per kwh. The upcoming BMW i3 will be pushing the 5 miles per Kwh threshold. For this analysis, as it looks at the next 25 years of driving, we will assume a 5 miles per Kwh efficiency.
One KW of solar PV will generate approximately 1550KWHs of electricity annually thus generating 38,750Kwhs over the 25 years. It should be noted that there is a slight degradation of annual generation over that time, and that one inverter replacement will most likely be needed as well. However the system will last a far greater lifetime than the 25 years of warranty so we are going to call those data points a push.
5 miles per kwh multiplied by 38750 KWHs equal 193,750 miles driven for the energy cost of $3700. It also provides certainty of energy cost, as the sun never increases it’s price. That’s 1.9 cents per mile. Using the fleet average of 21 mpg, that’s the equivalent of $0.40 cents per gallon of gas.
But it gets even better. We are on a TOU rate schedule and get paid $0.30 cents per Kwh that we generate in excess during the peak hours of the day. We pay $0.14 to use the super off peak energy to charge the car at night. We calculate this to be an additional 30% savings. (weekends don’t count, summer is better than winter) thus lowering our cost to $0.25 -$0.30 cents per gallon equivalent.
Cheers
Peder