Over the last few years, several large rental firms have helped the electric car cause by adding plug-in vehicles to their rental fleets.

In theory, it's the ideal people to get people into electric cars in general--some seat time is usually enough to convince people that EVs are the way to go.

The good news is that people are certainly renting those cars. The bad news is that they aren't doing so for very long, and it's due to a familiar electric car sticking point: range anxiety.

According to Bloomberg, customers trying out Nissan Leaf electric cars as part of Enterprise's rental fleet are swapping them for more conventional cars after 1.6 days on average--compared to the six or seven day period for cars on average. The number one cause is customers worrying whether they'll make it to a charging station before the battery runs out.

"People are very keen to try it, but they will switch out of the contract part way through" said Lee Broughton, head of sustainability at Enterprise, to Bloomberg.

With customers not hanging on to electric cars as long as expected, the company's fleet of 300 electric cars nationwide is 40 percent lower than its original target of 500--demand just doesn't justify supply right now.

It's the same story at Hertz, which is also seeing lower-than-expected demand, even though it had some early success with the formula.

It isn't all bad news, though. Despite low usage, the major rental companies still have plans for increasing their electric car ranges--just better targeted for demand.

Secondly, the subtext to these short-term rentals is that customers really are curious about electric vehicle technology and seem happy to rent the cars, even if they don't keep them for long. The interest is clearly there, though the paucity of electric cars on fleets mean choice is limited to just a handful of different vehicles.

Finally, there's always the top of the rental market: exotic vehicles. Both Hertz and Enterprise offer the Tesla Model S on their rental fleets--provided you have around $300-$500 per day to spend. Each company offers the sedan as part of their high-end luxury options. The car's long range and its billing as a unique experience mean it sidesteps some of the more conventional cars' shortfalls.

Have you rented an electric car? Share your experience with us below.

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