(USA TODAY) -- Plug-in electric cars may be cutting-edge technology, but an analysissuggests that most will depreciate more dramatically over five yearsthan their conventional counterparts.

Some of the biggest valuegaps involve 2014 models powered only by batteries, entirely without gasengines, according to the analysis performed by Kelley Blue Book at therequest of USA TODAY. Examples:

•Chevrolet Spark EV. Thelittle electric is projected to be worth 28% of its $28,305 list pricein five years, while a comparable conventional version of the same carwill retain 40% of its value.

Ford Focus Electric. Thecompact will be worth 20% of its initial $35,995 list price, while awell-outfitted conventional Focus Titanium with an automatictransmission will still command 36%.

Nissan Leaf. Even thebest-selling pure electric car is projected at having a residual valueof 15% for the 2013 model. A similar Nissan Sentra SL compact wouldretain 36%.

"Pure electrics have been slow to catch on in theresale market," says Eric Ibara, director of residual consulting forKelley Blue Book. Customers "have been willing to buy a new one, not aused electric vehicle."

Indeed, three electric cars - Leaf, Fiat500e and Smart Fortwo electric - topped the list of models projected byKBB to have the highest depreciation among all cars and trucks for the2014 model year.

Tackling concerns about depreciation, TeslaMotors CEO Elon Musk announced in May that he would personally back theresale value of its Model S all-electric sedan for buyers who useTesla's finance program. Tesla said that under the deal, resale valuewill be higher than BMW, Mercedes-Benz, Lexus or Jaguar.

As bad asthat sounds, there are some mitigating factors. In particular, manybuyers are given sales incentives packages and don't pay anywhere nearthe list price. Some of the biggest discounts come on leases. And manyelectric cars qualify for a federal tax credit of up to $7,500, plusstate or local incentives. Big discounts on news cars hurt residualvalues.

Plug-in hybrid cars, those with backup gas engines, fairbetter, KBB reports. For instance, Porsche's new Panamera E-Hybrid has apredicted resale value of 37%, compared with 41% for the conventionalmodel. Toyota's Plug-In Prius has a resale of 35%, only 2 percentagepoints less than for the conventional version.

Nissan officialsnote the electric car, or EV, revolution is still in its infancy. Themarket for used electric cars is yet to develop.

"We expect to seea similar adoption curve for used EVs as we have for new EVs, and weare just now reaching the point where there are used EVs on the market,"says Erik Gottfried, director of marketing for Nissan Leaf. "EVs areone of the most active and fast-moving segments of the automotivemarket."

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