A home solar system produces electricity during the day. Most electric car owners plug in their EVs at night. If you plug in at night, you’re not using solar electricity to power your EV. The electricity flowing into your EV’s batteries is being produced by whatever the night-time grid mix is where you live.
So, basically, in most solar-charged driving cases, at best, you’re using so-called solar-offset electricity, meaning your home solar system generates extra electricity during the day, for which you get credit, and you tap into that credit at night when you plug in a car.
Don’t get me wrong: Tapping the solar-offset electricity “bank” to power an EV is a great thing, especially economically.
While waiting, seemingly endlessly, for production EVs to arrive in Colorado, we’ve generated about 4,200 kWh of banked solar-offset electricity, or the equivalent of more than $2,000 worth of “gasoline” (25 mpg, $3.50 per gallon, 3.5 miles/kWh).
Yes, the 4,200 extra kWh we’ve pumped into our neighborhood grid, and the possibly 10,000 extra kWh we will have pushed into that same grid by the time production EVs arrive – finally! – in Colorado, have definitely cleaned up the grid locally, during the day, that is.
Our solar-generated kWh mean that a neighbor’s air conditioner, dryer, electric range, etc. is often partially solar-powered — although I bet none of my neighbors know this, or even give any thought to it, actually.
But even though the thousands of solar-offset kWh we’ve banked will save us a lot of money and even though they are helping to clean up the local grid during the day, they won’t be powering our EV.
If we plug in at night – and there’s really no other way for us to access our banked solar-offset kWh – here in Xcel Energy territory on Colorado’s Front Range, our EV’s batteries will be filled with electricity generated primarily by a mix of coal and natural gas. That’s not a good feeling for me.
Plugging in at night If we plug in at night – and there’s really no other way for us to access our banked solar-offset kWh – here in Xcel Energy territory on Colorado’s Front Range, our EV’s batteries will be filled with electricity generated by a mix of coal and natural gas.
That’s not a good feeling for me. I don’t like the fact that coal will be the primary “direct” fuel for our future EV.
And, even though every single mile we eventually drive in our new EV will be, at the very least, a solar-offset mile, even though our 5.59 kW home solar system has pumped out thousands of extra kWh in its first 11 months, even though that same system will cover 100 percent of our electricity use with one EV, and, with the thousands of kWh we’ve banked, will actually be enough to power 100 percent of our home electric use plus two EVs for several years when you take into account all of our solar-offset electricity, in the end, we still will have not managed to escape the trap of Dirty Coal.
Thousands of kWh of sun electricity Is what we’re doing better than plugging in without having added thousands of extra kWh of daytime sun electricity to our local grid?
Frankly, though, just how much good it’s actually doing, I can’t really say – because I’m too mathematically challenged to figure out, and then crunch, the many different numbers in play in a solar-offset-charged scenario such as our own.
But even if I could figure it all out for our specific solar-offset-charged situation, we’d still be left with the (not-so?) dirty secret of all grid-tied solar households: Whether you’re talking about solar-charging a car or solar-powering a refrigerator, if you’re doing so at night, through solar-offset, unless you’re lucky and live in an area with high-levels of hydro and/or wind power, you’re likely to be still very much reliant on, yes, Dirty Coal — and you will be until our society finally invests in, and plugs into, the holy grail of clean, renewable energy: Energy storage.
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