Lower maintenance and repair needs plus lower energy costs can make a very convincing case for electric car ownership.

The same isn’t always true for those who own vehicles the old-fashioned way, going with what’s new and fresh every three years or so, before trading it in for the next. Then, electric vehicles have an issue that can turn the math on its side: appalling resale value.

The average new electric vehicle loses 56.6 percent of its original value in three years, according to the car-deal search engine iSeeCars. The average among all kinds of vehicles is 38.2 percent of depreciation over three years.

The depreciation is from its sticker price, so it doesn’t include things like a potential EV tax credit of up to $7,500—which not every buyer may be able to claim.

In a recent analysis, iSeeCars found that the Fiat 500e had the steepest value plunge among EVs. Its average three-year-old used price was just $10,358—a depreciation of nearly 70 percent from its original price. The BMW i3 after three years cost just $19,784, which was a 63-percent cut from its original price. The Nissan Leaf (despite hints of an uptick last year) and Volkswagen e-Golf also posted steep value losses of nearly 60 percent over three years.

2018 BMW i3s

2018 BMW i3s

The Ford Fusion Energi was also called out by iSeeCars a plunge in value that was nearly as steep as that of those EVs. The Fusion Energi is worth just $15,983 after three years.

The new trends come from an analysis of more than 4.8 million car sales, comparing average price weighted by sales volume for vehicles sold between January and May 2019 with those of the same model sold between January and May 2019, adjusting for inflation via the U.S. Bureau of Labor Statistics.

2019 Tesla Model S

2019 Tesla Model S

Tesla is an exception to the rule, though—and proof that EVs don’t have to be resale-value money pits. After three years, the average Tesla Model S remains worth a strong $57,517, according to iSeeCars, which is just a 17.1-percent reduction from its price when new.

For nearly all the other non-Tesla models, these losses help enforce the value of leasing (under what are in many case highly subsidized offers), while purchasing may only make sense when planning to keep an EV over a longer timeline.

All of the electric models that lost the largest chunk of their original value are short-range models. One of the keys to success (and a signal of success) for the new long-range fully electric vehicles is that they escape the pull of strong depreciation. With the first Chevrolet Bolt EVs due to near that three-year mark early next year—and the new ones in their tax-credit phaseout—we’ll start getting some answers on whether that's the case in a matter of months.