Sunday, October 23, 2011

Solar Energy Beats Gasoline By A “Clean Country Mile” It takes a lot of energy to make gas... Part three.

Continuing on with my financial analysis of the energy cost to power gasoline and electric cars.

As you know by now, I power my BMW Electric Mini-E by solar energy. I drive on sunshine. 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.

Each KW of a solar PV system cost approximately $3700 when part of an average sized residential system. The space required for that one KW is about 60 sq feet, about half the size of a small bedroom.

In California and other sunshine states, that one KW will generate approximately 1550KWHs of electricity annually. The solar PV warranty is 25 years, 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 (think of a pane of glass and how long that last) so we are going to call those data points a push.

The cost of driving an electric car powered by sunshine 7,750 miles per year.

Electric cars are evolving quickly, 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.

5 miles per kwh multiplied by 38750 KWHs equal 193,750 miles driven for the energy cost of $3700. This works out to to 7,750 miles per year, and a cost of $148 per year, per kw of generation. It also provides absolute certainty of energy cost, as the sun never increases it’s price.

The cost of driving 7,750 mile per year powered by gasoline.

Over 25 years the gas at today’s mpg efficiency, a car travelling 7750 miles per year will consume 8800 gallons of fuel. Using the US fleet average of 22mpg, driving 7750 miles a year, a gasoline car will consume 352 gallons of gas or $1442 for the first year at $4.00 per gallon. And no you’re not reading this wrong, a solar pv system cost is the same or less than buying gasoline for three years ($3700 total cost for solar vs. $1422 annual cost for gasoline.).The next 22 years of driving the EV are on the "house of the rising sun" :)

Let’s be generous and assume that the gasoline car fleet averages 40 mpg during the next 25 years beginning at 22mpg of today and ending at 60mpg in 25 years, That would be an average of 194 gallons annually and 4850 gallons of fuel for the nest 25 years. With a modest multiplier of 3% annually for the increase in gas prices you’re looking at $35,000 in fuel cost for the next 25 years. If gas prices and cars maintain their current 22mpg fleet average, that number would be approaching $80,000. If crazy stuff happens in the oil supplying regions and  global consumption increases dramatically, your guess is as good as mine. This is the uncertainty of energy cost.

To summarize,

At a fleet average of 40mpg, a gasoline car will use 4850 gallons of gasoline which will cost $35,000 to drive  7750 miles per year for the next 25 years

An Electric car driving on Solar will require 60 sq. ft. of space, $3,700 in cost to drive  7,750 miles per year for the next 25 years.

"The answer my friend, is blowin in the wind." The answer is the ""sunshine on my shoulders."  It cost 1/10th (and is dropping in price) as compared to gasoline.



Mini-E #183, 34,000 sunshine powered miles.

Song title credits:
The Animals
Bob Dylan
John Denver


  1. First there were a few dozen, then a few hundred (Mini-E & Tesla) then a few thousand, then 10’s of thousands, (Leaf and Volt), very soon hundreds of thousands and soon millions of EV drivers.

    Each and everyone an ambassador of sorts leading this country to a brighter future.
    Keep on Keeping on and thanks for the comments!

  2. If you install a solar panel in your house, you are tapping into this massive source of free energy, and slashing your fuel bills. There are also great environmental benefits to solar energy, as it produces no pollution.

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