Although Tesla is facing increasing challenges from traditional manufacturers, its sales show no sign of weakening. One of the established automakers’ biggest challenges may be infrastructure.

That’s according to JD Power’s inaugural EV Experience Ownership Study, which seeks to measure owner satisfaction with EVs.

By and large, the numbers are good for EVs. Out of 1,000 points, based on factors like battery range, availability of public charging stations, battery range, cost of ownership, driving enjoyment, ease of charging at home, and vehicle quality and reliability, the average satisfaction result among premium EVs is 782, with Tesla’s Model S and Model 3 leading the pack, and the Model Y and Model X following. Meanwhile mass market EV satisfaction is at 730 points, with the Kia Nero EV, Chevrolet Bolt and Hyundai Kona EV taking the three top spots.

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That means that owners are, overall, pretty happy with their electric cars. And that’s good news for manufacturers, because 77% of drivers whose satisfaction ranks between 600 and 750 say they will definitely buy another EV.

The bad news for automakers, though, is that only 25% of those same people are likely to buy from the same brand. Drivers of the e-Golf, for example, whose average satisfaction ranks at 696, may not want to go back to Volkswagen for their next EV.

Indeed, the e-Golf’s 125-mile range doesn’t position it well for high satisfaction. JD Power found that range, as well as accuracy of range estimates, is the single most important factor in driver satisfaction.

With most of the modern crop of EVs coming with 200 to 300 miles of range, though, the charging network become the real differentiator. Satisfaction among owners of premium EVs with widely available public charging points is 235 points higher than those without.

Location is still a strong determining factor in access to public charging. Drivers on the West Coast are pretty well served, whereas those in the Midwest not so much. But brand still matters.

Tesla drivers are, on average, 305 points happier with their charging network than drivers of other brands. Electrify America, the charging network company set up by Volkswagen after the Dieselgate scandal, currently has 538 charging stations in North America, with 144 coming soon, according its website. Tesla, meanwhile, has 2,000.

Although Electrify America’s network was large enough to get a Porsche Taycan across the U.S. in record time in December, that’s kind of beside the point if the one charger within range of you is out of your way.