What is electric car sales' biggest challenge? Car dealers.

Car dealers maximize their profits by selling the highest number of cars at the highest possible prices in the least possible time.

Plug-in electric cars are unfamiliar to most buyers, and require more explanation – sometimes a great deal more – along with specific types of support during and after the sale.

That makes them less appealing for dealers to sell, especially the higher-volume dealers.

Now a third party, specifically the Natural Resource Defense Council's Luke Tonachel, has highlighted the challenge to electric-car adoption posed by the dealership bottleneck.

In a recent article in trade journal Ward's Automotive, he highlighted the dissatisfaction rate with the dealership process among consumers seeking to buy an electric car, which was a remarkably high 83 percent.

For buyers overall, that rate stood at just 25 percent.

The data he cited came from ongoing research at the University of California--Davis, which has long studied adoption of plug-in vehicles, including the motivations, practical challenges, and the step-by-step process.

Tonachel recounted instances where salespeople actively steered informed shoppers away from the plug-in vehicle they had specified they wanted to buy.

“Sales people wanted to sell something else," Tonachel explained, "and would say, ‘Maybe you should look over here.’"

Many dealerships that had been certified to sell and service their brand's plug-in vehicles either didn't have them on the floor, didn't have test cars available, or only grudgingly agreed to provide test drives in the electric vehicle.

Similar results have emerged from secret shoppers sent on behalf of Consumer Reports to ask about and shop for electric vehicles at dealerships.

Tonachel spoke at a conference on fuel economy held by the University of Michigan's Transportation Research Institute.

The event's host, Bruce Belzowski, urged dealerships to prioritize having electric cars on the lot, and available for test drives.

Other advice he may have given: Ensure that at least one salesperson who actually understands the vehicles is present at all times.

Keep the cars recharged, so that no salesperson has to say, "Oh, you've only got 18 miles left, so keep your test drive short so you don't die at the side of the road."

Belzowski noted a similarity between diesel and electric vehicles at dealers: In both cases, sales outlets often had only a single model on the lot.

That presents the buyer with a take-it-or-leave-it choice of color, model, and options.

And that's not how you sell a lot of cars, as any experienced auto salesperson will attest.