Life is full of little ironies.

And life in the 50 states that make up the United States of America is full of inconsistencies, including those among electric-car incentives from state to state.

West Virginia, for instance, turns out to have offered offer a remarkably high income-tax credit of up to $7,500 for citizens (who can take advantage of it) who buy a battery-electric vehicle.

DON'T MISS: In Just One Year, Electric Cars Have Gotten Cleaner: How'd They Do That?

UPDATE: West Virginia's tax credit for Alternative-Fuel Vehicles remained in effect for several years, but in 2013, the state's legislature redefined which types of vehicles were eligible for the credit.

Electric cars purchased after April 14, 2013, no longer qualify for the credit, which is now restricted solely to vehicles fueled by natural gas and liquified petroleum gas.

We thank all the readers who not only pointed out our mistake but also sent references and further background. Green Car Reports apologizes for our error.

ADDITIONAL UPDATE: Reader Robert Bruninga also points out that West Virginia has a $2,000 state tax credit for installation of home photovoltaic solar panels.

The irony comes because West Virginia has the filthiest power grid among all 50 states--or, more accurately, the grid with the highest carbon dioxide emissions per kilowatt-hour.

According to the U.S. Energy Information Administration, the carbon intensity of a kilowatt-hour of electricity produced in West Virginia in 2011 (the most recent data provided) was 80.8 kilograms of CO2 per million BTUs.

That's the highest of any state in the nation.

Electric-car wells-to-wheels emission equivalencies in MPG, Sep 2014 [Union of Concerned Scientists]

Electric-car wells-to-wheels emission equivalencies in MPG, Sep 2014 [Union of Concerned Scientists]

It's higher than the national average of 55.3 kg/million BTUs, and 63 percent higher than the 49.5 reading in California (which accounts for up to half of all plug-in electric vehicle sales in the U.S. these days).

That doesn't mean that driving an electric car in West Virginia is worse than a gasoline car; even on the dirtiest grids, the carbon footprint of an electric car is equivalent to a gasoline vehicle of at least 30 miles per gallon or more.

But it does mean that in West Virginia, a 50-mpg Toyota Prius may have a slightly lower carbon footprint than an electric car--which is not the case in the vast majority of states. West Virginia loses simply because its grid is so coal-heavy.

As for the California comparison, it's worth noting that the Golden State's grid has gotten progressively cleaner since 2011, with an aggressive state program toward a goal of boosting use of renewable energy by 50 percent from current levels by 2030.

ALSO SEE: EPA's Coal-Plant Emissions Rules: This Will Be The Big Fight

That's one advantage of cars fueled by grid electricity, of course: As the grid gets cleaner, so does each mile driven in a plug-in car. Gasoline and diesel cars, by contrast, can't cut their carbon per mile unless they use lower-carbon fuels--which are rare at best today.

The West Virginia incentives for purchase of a plug-in vehicle, according to the informative Plug-In America page that tracks all state incentives, had been is:

Income tax credit of 35% of vehicle purchase costs or 50% of conversion cost, up to $7,500 for vehicles less than 26,000 lbs and up to $25,000 for vehicles greater than 26,000 lbs. Expires Dec 31, 2021.

Infrastructure tax credits of 50% of installation cost, up to $10,000 for residential, up to $250,000 for commercial, and up to $312,500 for publicly accessible charging.

EDITOR'S NOTE: Plug-In America has since updated its article to reflect the eligibility changes to West Virginia's Alternative-Fuel Vehicles tax credit.

Coal Mine

Coal Mine

That's among the very highest state incentive programs in the nation, even exceeding Georgia's now-ended $5,000 tax credit for purchase of an all-electric car.

We learned about this little irony from an article on ChargedEVs covering a new report from Carnegie Mellon University that says, essentially, that the carbon footprint of an electric car depends on the grid it's charged from. No surprise there.

EDITOR'S NOTE: ChargedEVs has since updated its article to reflect the eligibility changes to West Virginia's Alternative-Fuel Vehicles tax credit.

Coal, by Flicker user oatsy40 (Used Under CC License)

Coal, by Flicker user oatsy40 (Used Under CC License)

The article notes that under specific circumstances, nighttime charging may have a slightly higher carbon footprint because in some states, the base-load power generation has a higher proportion of coal in the mix than at any other times with higher loads.

But as Charged EVs put it, the report also notes that, "Differences in state subsidies do not align well with regional difference in carbon efficiency."

Indeed.

Not to worry, though: Conversations with electric-car makers indicate that West Virginia is, shall we say, not high on their list of target markets--for any number of reasons.

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