Over the years, we've noted the paucity of solid data on the intersection of home solar energy and driving plug-in electric cars.

A California-only study from 2012 still gets quoted occasionally, and we continue to seek more recent and more comprehensive data.

Out of a mix of curiosity and desperation, we turned to our (far from scientific) weekly Twitter polls to get some (possibly very unrepresentative) responses.

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We asked our Twitter followers who own or lease electric cars what kind of electricity they used to charge the vehicle at home.

The first choice of the four possibilities—standard electricity coming across the grid—was the one we suspected would draw the largest single number of responses.

And that's exactly what happened.

Of our poll participants, 44 percent said they just plugged their cars into the standard grid, with whatever mix of low- or high-carbon electricity it might contain.

Since roughly half the plug-in cars in the U.S. exist in California, that state's fairly clean grid means lots of U.S. electric cars are being charged on low-carbon electricity.

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But the next most popular response, at 37 percent, was charging the electric car on grid-linked home solar power.

In other words, solar panels on the roof that power some or all of a home's energy needs and feed excess energy back into the utility grid, known as "reverse metering."

Photovoltaic solar panel installation on house, Fremont, California [image: Shiva Singh]

Photovoltaic solar panel installation on house, Fremont, California [image: Shiva Singh]

The only other choice with a notable response was the 17 percent of participants who said they paid their electric utility to supply them with renewably generated electricity. (In theory, anyhow: electrons are fungible.)

A mere 2 percent of respondents, or no more than 10 people, said they charged their plug-in cars using off-grid solar or wind energy.

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As always, please note that our Twitter polls are far from scientifically valid, due to small sample size and self-selection by those who choose to participate.

Now, would someone please find us better and more scientifically valid data on electric-car owners and home-solar users? Please?