This story originally appeared on Grist and is part of the Climate Desk collaboration.

Electric vehicles (EVs) have a clear environmental advantage over their gas-guzzling counterparts, but when it comes to longevity, the two are in a dead heat. Two hundred thousand miles is considered a good, long run for a car built today, regardless of whether it’s powered by a lithium battery or an internal combustion engine. But if a flurry of recent reports are to be believed, EVs may soon surge ahead in this long-distance competition—not by mere thousands of miles, but by 800,000.

Recently, multiple EV battery makers have announced the imminent arrival of “million-mile” batteries, power packs that supposedly have enough juice to be driven to the moon and back twice. In May, a top executive at General Motors said the company was “almost there” on development of a million-mile battery; in June, Chinese battery maker Contemporary Amperex Technology Co. Ltd. (CATL) told Bloomberg it was ready to produce batteries that last 1.24 million miles. For months, rumors have swirled that Tesla will soon roll out a million-mile battery on its own. Its 2019 Impact Report, released in early June, certainly reinforced that impression when it emphasized the environmental advantages of a “future Tesla vehicle with a million mile battery.”

But what does the million-mile battery revolution actually mean? According to experts in battery storage technology and the EV market, claims of new batteries that will last a million miles don’t tell us much on their own. How these batteries can be used is going to depend, first and foremost, on how they perform and degrade over their so-called “million-mile” lifespan. Several experts pointed out that true million-mile batteries are likely to outlast whatever cars they’re built for, meaning their arrival could dramatically impact both second-use markets and battery recycling.

“What they’re talking about with million-mile batteries is not so much that an average consumer would put a million miles on the clock,” said Simon Lambert, a co-lead investigator at the Recycling of Lithium-Ion Batteries project (ReLiB) at the UK’s Faraday Institution, “but that you’d potentially be able to use the battery multiple times, either in vehicular energy storage or grid-connected stuff.”

Most EV batteries on the road today—nearly all of which are lithium-ion batteries employing one of several different chemistries—are warrantied to last 8 to 10 years or 100,000 miles. Some automakers guarantee that the battery will retain at least 70 percent of its original capacity over that period, meaning the car’s range—the distance it can drive before needing to be charged—won’t degrade by more than 30 percent.

In practice, early data suggests today’s EV batteries often last considerably longer with less degradation, said James Frith, an energy storage analyst for BloombergNEF, an clean energy research firm. Tesla’s recent impact report, Frith notes, claims that Model S and X batteries lose less than 20 percent of their original charge capacity after being driven 200,000 miles. A Nissan executive, meanwhile, recently estimated that a Nissan Leaf battery will last about 22 years based on battery degradation data the company is collecting on EVs sold in Europe, according to Automotive News.

“We’re only just getting to the point where we’ve had EVs on the road for 10 years, and we can really see how well those claims of battery life last,” Frith said. “But in general, we see EVs do tend to perform quite well.”

In many cases, EV batteries are already outlasting the cars they are being put in. Hans Eric Melin, the founder of Circular Energy Storage, a market research firm focused on second-use and recycling of lithium-ion batteries, says that it’s “very unusual” for a car to be pulled off the road today because its battery has degraded fully. While this is sometimes the case for heavily-driven electric taxis or Ubers, more often, the battery experienced some sort of electrical malfunction, other components of the EV became worn out, or the car was totaled in a crash.