editors-blog-entry3Look out: The solar purists are on the prowl, and they very definitely don’t like the idea of viewing gasoline costs as being offset by a home PV solar system.

In other words, they don’t very much like what we’re doing here at SolarChargedDriving.Com where we’re using a simple formula to calculate gasoline savings produced by our 5.59 kW home solar system.

The formula:

  • 1 kWh = 4 miles in an electric vehicle
  • Gasoline cost = $3 per gallon
  • Miles per gallon rate = 20 m.p.g.

Extra kWh available for future use
So far, our 5.59 kW solar system has generated 2,626 kWh more than we’ve used. Thanks to our utility’s indefinite kWh rollover option, we’ve “banked” these kWh – which we continue to add to almost every day, even in the thick of winter.

This means they’re available forever for future use. And we’ll definitely be using these banked kWh as future EV miles – once we get an EV.

rip-take1Our first EV will replace one of our aging gasoline cars – a 1992 Acura Integra that I bought new nearly two decades ago, or a 1994 Toyota Camry with 270,000 miles on it.

That means no more gasoline money being spent to fuel one of our two household cars.

Using the equation above, 1 kWh = 4 EV miles, $3 per gallon/20 m.p.g., and 2,626 banked Sun Miles, we’re at $1,576 worth of gasoline savings so far – with much more savings to come.

Granted, the equation is a rough one, and the total savings can vary based on changing the inputs.

This is part of what apparently sent one reader of a column I re-published on RenewableEnergyWorld.Com about the gasoline savings our home solar system was generating into a tizzy.

Comparing apples to oranges?
Among other things, the reader took me to task:

  • for “being misleading”;
  • for “comparing apples to oranges”;
  • for “hiding the real cost of (our) solar array in the EV”;
  • for the fact that the m.p.g. rate of the gasoline car can be changed, or, as she put it, “your old gasser determines the payback time of your array. That doesn’t make sense.”
  • And, finally, for — get this! — giving “greenies a bad name,” apparently because I’m allegedly trying to snow people under with the claim that a home solar PV system coupled with an EV can produce thousands of dollars of savings by replacing the gasoline + internal combustion engine combo;

We went back and forth a few times in the comment strings, with neither one of us convincing the other.

My final set of comments to ‘annevanderborn’, challenged her to give me an answer on what she would do with the couple of thousand kWh we’ve banked.

I wrote:

“We have 2,500 kWh banked with our utility. How would you use those hours, and why:

a) cash them in for $175? (yes, this is the pathetic payment Xcel Energy would give us for 2,500 extra kWh!)
b) use them to power an electric device in the house, say an electric heater, which basically means each kWh = 11 cents (that’s the rate we pay our utility), for $275 worth of electricity?
c) save them to power an electric vehicle which, in our case, will replace one of our two gasoline cars, each of which get about 25 mpg. The equation: 2,500 kWh (4 miles/1 kWh) = 10,000 miles in an EV; gasoline offset costs = $1,200 at $3/gallon?”

stop-using-gas2Solar as fuel for an EV
‘Annevanderborn’ never responded, though I’m wondering what she would do if she had those extra kWh banked and why.

Seems to me the smart thing to do is to save the extra kWh to fuel an EV.


Because you save the most money doing this — by far.

This is true even if you increase the m.p.g. rate to 40, 50, 60, 70 m.p.g. In fact, you’d have to up the m.p.g. rate all the way to 100 m.p.g. before you approached the value of the electricity produced by our home solar system if it were used to power a toaster, a refrigerator, etc. at 11 cents per kWh.

Solar + EV value
That value is a direct result of the type of electric item, in this case, an EV, that one is plugging in and which is using the electricity generated by a home solar system.

An EV is not a gas car. I get that.

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But those thousands of dollars we would have forked over for gasoline, well, we won’t be handing them over to Big Oil as a direct result of the fact that: a) we will soon have replaced our gasoline car with an EV; b) and the fact that we have a home solar system that’s generating the fuel for that EV.

Oh, and we won’t be paying anything to our electric utility for the kWh we’ll soon be pouring into our new EV’s batteries either.

If our home solar system is not responsible for producing these savings, what is?

What’s your take – and what would you do with 2,626 banked kWh, and why?

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