By now, it is common knowledge electric vehicles (EVs) are better for the environment than gas cars, because they are more efficient and don't directly emit harmful gases that warm the planet. However, I am occasionally asked a slightly different question which is harder to answer. Say you have a perfectly good gas-powered car that may last several more years. Is it still environmentally friendly to replace it with an EV?
The complicating factor here is that all cars require a lot of energy to build. All the parts have to be made, transported around the world to assembly factories, built, then finally transported to the dealer or customer. Before a car has been driven a single mile, it already has had a substantial environmental impact. And EVs have an even greater environmental impact prior to that first mile because batteries require minerals that take lots of energy to get out of the ground and into usable form.
Indeed, there is generally an assumption in the right-to-repair and sustainability world that using products as long as possible is better for the environment than buying new ones for this exact reason. In most cases, such as with phones and laptops, that assumption is correct, because most of the emissions from such devices occur before customers ever receive them. While roughly 10 percent of the life cycle emissions of gas cars comes from manufacturing, 85 percent of the life cycle emissions of, for example, the iPhone 12 come from manufacturing. Nearly all of the emissions produced by gas cars happen on the road. This, combined with how much less EVs emit from day-to-day use relative to their gas counterparts, drastically alters the conventional wisdom.
A quick caveat before we dive into the details: the figures used here will be generalities and averages because they vary by region depending on how much electricity comes from renewable energy sources like wind and solar versus sources that emit greenhouse gasses. That being said, the electricity grid is getting cleaner all the time, so the numbers are likely to improve in the favor of EVs in the future.
Also, none of this is to say EVs are good for the environment. People who are able to bike, walk, or take public transportation for the majority of their trips are going to generally have lower emissions than an EV owner. Even a Tesla Model 3, the most efficient EV on the market today, emits approximately 36 tons of CO2 over 200,000 miles of use, according to a Wall Street Journal analysis in conjunction with University of Toronto researchers. But that's about half of what, say, a Toyota Rav4 would emit over the same life span. In fact, it would only take about 20,000 miles—less than two years of driving for the average U.S. resident—for the higher manufacturing emissions of the Model 3 to be offset by the more efficient driving. A 2020 analysis by BloombergNEF found similar results. And as you can see from the included graph on BloombergNEF's study, even removing the manufacturing emissions from the gas car's calculations—because, in the scenario in question, you already own it—doesn't significantly alter the math. It only pushes the break-even point back a bit.
There are two main variables in deciding whether replacing your used gas car with an EV is better for the environment than not. The first is how many miles you plan to keep driving your gas car for. The more miles you plan to log on it, the more likely it is that buying a new EV is the better option for the environment. The second is how the electricity in your area is produced. The Union of Concerned Scientists has a helpful tool that equates the emissions for charging an EV in your zip code with a miles-per-gallon equivalent from a gas car. For example, charging a 2019 Tesla Model 3 Mid-Range in my zip code "produces about as much global warming pollution as a gasoline vehicle getting 117 miles per gallon."
As a very, very rough rule of thumb and erring on the conservative side, it is probably only better for the environment to keep your used gas car if you think it has less than 50,000 or so miles left in it. If you plan to put more than that on the gas car currently sitting in your driveway, it is almost certainly better for the environment to replace it with an EV.