About 15 million people buy a new vehicle in the U.S. each year, on average--but almost 40 million buy used cars in that same year.

Modern electric cars have been sold in the U.S. since December 2010. Not surprisingly, they're started to show up on used-car lots.

Should you buy one? The answer, of course, depends on your individual needs. But a used electric car can be a very good deal in many circumstances.

You need to evaluate your personal needs, how you plan to use the car, and how much uncertainty you're willing to accept.

2011 Nissan Leaf 4-door HB SL Dashboard

We've chosen to focus on the Nissan Leaf because not only is it the highest-production electric car in the world, it's now the best-selling plug-in car in the U.S. as well.

The Leaf beat the Chevrolet Volt range-extended electric car a few months ago. (We'll focus on used Volts in a separate article.)

[EDITOR'S NOTE: We thank the many readers who suggested updates and additions to this article. We suggest all readers browse through the comments for the wealth of practical information from current Leaf owners. We've updated this article with added sections on Quick Charging and Insurance, as well as tweaking some other sections.]

Here are the major issues, concerns, and questions that we're routinely asked about used electric cars.

While much of this article applies to specific details of the Leaf, it's worth reading for anyone considering the purchase of any used plug-in car.

ALSO SEE: The United States Of Used Cars

PRICE

The price for a used Nissan Leaf will vary depending on whether it's being sold privately or by a dealer, as well as its age, mileage, and battery condition.

In general, prices for cars bought from individuals will be lower than those from dealerships, for whom used-car sales are often more profitable than those of new cars.

We've heard reports of the oldest Leafs (from the 2011 and 2012 model years) now offered at prices of $9,000 to $11,000, but those are still rare.

2011 Nissan Leaf 4-door HB SL Grille

You can sort through used Leaf listings on The Car Connection and other sites to get a sense for what's available near you.

Remember that a new 2015 Nissan Leaf starts at $28,960, but that's for the base Leaf S model. High-end models can carry sticker prices of up to $35,000 or so.

Nissan has also added the Leaf to its Certified Used program, which will add a measure of reassurance for those who prefer to buy used cars checked by the dealer to ensure they meet strict guidelines from the carmaker.

DEPRECIATION

One of the immediate questions asked about used electric cars is usually, "Why did they lose their value so quickly?"

Indeed, compared to similarly-sized gasoline cars, used Leafs are generally offered at a lower percentage of their original sticker price--meaning their depreciation has been high.

This is due to at least two factors. First is unfamiliarity: With less than five years of history, buyers just don't know how used Leafs will fare when they're 10 or 12 years old.

2011 Nissan Leaf

Second, though, is a financial quirk. Remember that buying a plug-in electric car can qualify you for a Federal income-tax credit of $2,500 to $7,500.

The first owner of just about every used Leaf on the market, in other words, paid an effective price $7,500 lower than the sticker price--whether that owner was a private buyer or a leasing company.

When you re-run the numbers using that effective price, the depreciation doesn't look nearly as bad.

And, remember, there's pretty much a minimum value in your area for any decent running used car of any age. With higher depreciation incurred by the first owner, the second buyer could well lose less than for a comparable gasoline car.

2011 Nissan Leaf - battery pack

BATTERY LIFE

That will likely depend, however, on one of the biggest unknowns: How long will the battery of a Nissan Leaf last?

Anyone who uses a cellphone or a laptop computer knows that batteries degrade over time.

Let's be very clear: Your phone battery can be trashed in a year or two--and that is NOT the case with an electric car.

DON'T MISS: Nissan Leaf Battery Capacity Loss: Covered By Warranty, Now

All electric-car batteries are warranted against total failure for either 8 years/100,000 miles or 10 years/150,000 miles, depending on what state you live in.

And Nissan improved its warranty coverage for Leafs in spring 2013, making the new terms retroactive to 2011 and 2012 models as well.

The changes came in response to concerns over fast battery degradation in a very small number of Leafs in extremely hot areas--Phoenix, specifically.

The revised warranty also protects U.S. Leaf owners against battery-capacity loss during the car's first five years or 60,000 miles.

2011 Nissan Leaf 4-door HB SL Audio System

If the battery capacity gauge falls below nine bars (from 12) during that period, Nissan will repair or replace the battery under warranty with a new or remanufactured unit, "to restore capacity at or above a minimum of nine bars."

Nine bars equates to about 70 percent of remaining capacity--meaning that the effective range of a 2011 Nissan Leaf, originally rated at 73 miles, could be down to something like 50 miles.

Note, however, that very, very few Leafs have fallen to nine bars thus far.

MORE: Nissan Leaf New Battery Cost: $5,500 For Replacement With Heat-Resistant Chemistry

In fact, our colleague Nikki Gordon-Bloomfield's 2011 Leaf only lost its first bar (of 12) after 53,000 miles and more than three years.

Our advice: First, insist on seeing a current battery-capacity test from a Nissan dealer for any Leaf you are seriously considering.

Second, you may want to set a minimum level, perhaps cars with only 11 or 12 bars--though it's likely that Leafs with 9 or 10 bars will be considerably cheaper.

Lithium-ion battery pack of 2011 Nissan Leaf, showing cells assembled into modules

It all depends on how many daily miles you'll really put on the car, and whether you have access to battery charging at work.

If worst comes to worst, a replacement battery pack for a Nissan Leaf will run you $5,500. And that new pack will have an updated cell chemistry that is far more heat-resistant, Nissan promises.

2011 Nissan Leaf

Within a few years, we'll likely see more daring buyers bargaining hard for the very few Leafs no longer eligible for the capacity warranty and whose batteries may have fallen to 50 or 60 percent of capacity.

Less knowledgeable sellers or dealers may simply want to get rid of that car for a few thousand dollars.

That may mean that those daring buyers could have a new pack installed, and end up with a Leaf with the range of a brand-new model for $10,000.

2015 Nissan Leaf

MAINTENANCE

And here's why that might be a good deal: Battery-electric cars need very little maintenance.

With no belts or timing chains, no transmission, no oil changes, no spark plugs, and no muffler, the regular maintenance on a Leaf largely consists of:

wiper blades

cabin air filter

tires

motor coolant check

So check the tires and wiper blades on your used Leaf, ask the seller when the cabin air filter was last changed, and other than that, make sure all the electric accessories work.

Test the electric parking brake (on 2011 and 2012 Leafs only), the electric windows and mirrors, and make sure the air conditioning works.

That's pretty much all you need to worry about.

2015 Nissan Leaf

MODEL-YEAR DIFFERENCES

The 2011 and 2012 Leafs were made in Japan, and have a few detail differences from U.S.-market 2013 through 2015 Leafs built in Smyrna, Tennessee.

The first two years of Leaf have the onboard charger mounted between the two rear wheels, which intrudes on the cargo bay.

Later cars moved it up under the hood, so they have flat cargo floors--a useful modification for those who use their load bay regularly.

The early cars also had a 3.3-kilowatt onboard charger, slower than the 6.6-kW charger fitted to most (but not all) 2013-2015 Leafs.

2015 Nissan Leaf 4-door HB S Dashboard

Later Leafs have a more efficient cabin heater that uses less battery energy.

They also have a foot-operated "pendant" parking brake under the left side of the dashboard, replacing the switch for the electric parking brake on Japan-built models.

And the U.S. Leafs also gave up certain aluminum body panels that lightened the first Leafs.

Finally, a package of improvements to the motor, power electronics, and other powertrain components made 2013-2015 Leafs slightly more efficient.

With the battery fully charged, their range rose from the earlier 75 miles to 84 miles.

QUICK CHARGING

It's important to note that not every Leaf was sold with a CHAdeMO quick-charging port.

That's the separate connector, also under the charge-port door in the nose, that allows an 80-percent recharge in around 30 minutes--versus several hours using a more common 240-Volt Level 2 charging station.

While DC fast-charging stations are not evenly distributed throughout the country, certain regions have enough of them that the Leaf's practical daily range can be significantly extending with a half-hour stop.

There were almost no CHAdeMO chargers when the Leaf first launched, but now there are several hundred--so find out how common they are where you live.

If there are enough that your area is covered, or there's one on a route you commonly travel (or would like to), then you're well advised to ensure that you buy a used Leaf with a quick-charging port.

INSURANCE

While the very first electric-car owners sometimes found their insurance companies charging more than for other vehicles, insurance rates for the Leaf have settled down and are now comparable to those for other compact hatchbacks.

In fact, the Leaf is often slightly cheaper to insure than gasoline vehicles of the same size, because Leafs are expected to accumulate fewer miles due to their shorter effective range.

As always, shop around for the best rate. But you needn't worry that insuring a Leaf will be different from insuring any other car.

SHOULD I DO IT?

Just as the first buyers four years ago were pioneers, those who buy used electric cars are venturing into unknown territory.

Still, buying a used car always brings with it some uncertainty.

First 2011 Nissan Leaf delivered to buyer, San Francisco, Dec 2010, photo by Eugene Lee

For a used Nissan Leaf, the major item of concern--assuming it hasn't been wrecked--will be the battery life, along with whether all the accessories still work.

Market prices today reflect that uncertainty, and arguably this is a good time to buy a used Leaf precisely for that reason.

Since we know how much Nissan charges for a brand-new battery pack, you can calculate your worst-case scenario, and bargain accordingly.

There is one final warning, however.

Electric-car owners routinely report that drivers in their household fight over who gets to use the electric car each day--and who's relegated to having to use that noisy, vibrating gasoline car.

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