We had our carpets cleaned the other day, and when the cleaner guy found out what I did, the very first thing he said was, "I was going to get an electric car." Then he looked at me almost apologetically. "But I heard they're actually worse for the environment."

It's not the first time I've heard it. The media loves these stories. They're counterintuitive, surprising, and best of all, show that those silly greens, with their idealistic yadda yadda, don't know how to do math.

They're also wrong, as a new report from the Union of Concerned Scientists conclusively demonstrates. The two-year study digs into the life-cycle greenhouse gas emissions of battery electric vehicles and gasoline cars, from materials to manufacturing to operation to disposal.

The four cars used in the comparison were a midsize and a full-size gasoline car, a midsize battery electric vehicle (based on the Nissan Leaf), and a full-size BEV (based on the Tesla S).

Long story short: Electric cars really are cleaner.

Electric cars do have a slightly higher carbon footprint in the manufacturing stage, and each BEV also requires manufacturing a battery. But it turns out the vast bulk of auto-related carbon emissions come not from manufacturing but from operation — driving — and the savings BEVs represent on that score make up the difference by many multiples. (Disposal emissions are similar for both types of cars, and a small percentage of the total.)

Here are three quick conclusions from the study.

1) BEV manufacturing emissions are coming down and can be brought down faster

Those emissions are already falling, just from the efficiency of scale. UCS recommends three strategies to accelerate the decline:

Advances in manufacturing efficiency and in the recycling or reuse of lithium-ion batteries

The use of alternative battery chemistries that require less energy-intensive materials

The use of renewable energy to power manufacturers’ and suppliers’ facilities

2) BEV operating emissions are coming down and can be brought down faster

UCS did a similar study in 2012 that found the same advantage, but the advantage has only widened as the US grid gets cleaner. As coal plants continue to shut down, replaced by natural gas, wind, solar, and energy efficiency, the average emissions of a US kilowatt-hour declines. That means BEV fuel gets cleaner.

If the US grid achieves 80 percent penetration of renewable energy, the total emissions of a BEV would fall by another 60 percent.

3) BEVs are already cleaner than gasoline cars in every region of the country

This map shows the miles per gallon that a gasoline car would have to get to match the environmental performance of a BEV in each region of the country.

The lowest bar a gasoline car would have to clear — i.e., the dirtiest grid — is 35 mpg, there in the center of the country. That means if you want a gas car cleaner than an electric car, you have to live there, and you have to own one of two cars: the Scion iA or the Honda Fit, both of which will probably only be cleaner for another few years.

Electricity is the future

The larger meaning this study is that electricity is the future. It is getting rapidly cleaner, while the search for alternative liquid fuels remains halting and slow (or, in the case of VW and "clean diesel," in reverse).

Rapid electrification of the passenger vehicle fleet would not only substantially reduce the carbon emissions of the transportation sector, it would also serve as a huge new pool of electricity demand and storage, facilitating the growth of variable renewable energy like wind and solar.

The same can be said, on a somewhat smaller scale, of other sectors that now make heavy use of liquid fuels: heating and cooling, heavy transportation, high-temperature industrial applications. Electrification faces challenges in all those areas, but if the target is zero carbon or close to it, I'd bet on batteries over biofuels.

UCS also has a nifty interactive tool where you can put in your zip code and find out how cars, including hybrids, compare in your area. (It's a pretty easy choice out here in Seattle.)

Finally, if you're sick of all these words, here's a video summarizing the study: