Is it greener to replace your gas car now?
Conventional wisdom says the greenest car is the one already in your driveway. After all, a lot of energy went into the manufacturing and if you’re not driving it, someone else will. Might as well hang onto it.
Right?
Wrong, according to a new study. As it turns out, even if you bought a new gas car today and scrapped it tomorrow, replacing it with an electric vehicle would, in most cases, put less carbon into the atmosphere than continuing to drive the gas car. Even if you sell the gas car instead of scrapping it, the EV usually still comes out ahead.
The research, published in August in the journal Science, comes from Elliott Campbell, an environmental studies professor at UC Santa Cruz, and Roland Geyer of UC Santa Barbara. They modeled more than 400 gas, hybrid, and electric models across different power grids, driving habits, and battery sizes. Then they compared a gas car driven for its roughly 16-year life with one retired early for an EV.
In 92% of scenarios, the swap cut total emissions. Retiring a typical gas car in its first year lowered emissions as much as 58% over 16 years, and the EV typically earned back its manufacturing emissions in about three years.
The researchers even stacked the deck in the gas car's favor by ignoring the pollution already created when it was built. The gas car entered the comparison with a clean slate and was judged only on the fuel it would burn from then on. The EV, by contrast, was charged in full for the carbon it took to build, including its battery, before it drove a single mile. Even with that handicap, the EV came out ahead 92% of the time.
Why efficiency wins
It comes down to efficiency. A gasoline engine turns only about 20% of its energy into motion. Let that sink in: Roughly 80% of the energy in every gallon is lost, most of it as engine heat.
An EV on the other hand puts roughly 90% of its electricity to work. Because fuel, not manufacturing, accounts for most of a car's lifetime emissions, that gap more than makes up for the extra carbon it takes to build a battery. What’s more: The advantage only grows over time as the grid adds more wind and solar.
When to keep your car
There are exceptions. Plug-in hybrids are efficient enough that trading one in early can actually raise emissions. So can replacing a top-tier hybrid on a grid with a heavy fossil fuel mix, because the per-mile savings shrink enough that the payback can stretch past the car's useful life.
Cars driven fewer than about 4,400 miles a year aren't worth replacing on climate grounds. Cost matters, too: the researchers don't actually recommend junking a car you just bought.
What it means in Colorado
Colorado's grid still leans partly on coal and natural gas, but the study found that replacing the most common gas models early cuts emissions even on the dirtiest U.S. grids.
If you’re looking to get rid of your gas car, help is available. Vehicle Exchange Colorado gives income-qualified residents $9,000 toward a new EV or $6,000 toward a used one when they retire an older or high-emitting vehicle. The state's EV tax credit also adds up to $3,250 on qualifying new models priced under $35,000.
