The roll-out of the Chevy Volt and Nissan Leaf electric cars in recent months has ignited a debate over this new technology.

Skeptics are posing questions about possible ghosts in the machine, wondering how long the batteries will perform at top level, worried about the length of the battery life, and want to know what it will cost to replace a battery if required.

If those questions sound familiar, it's because skeptics were asking the same kinds of questions about hybrid-car technology almost 11 years ago, when the Toyota Prius was making its debut in the U.S. market.

Fast forward to today. Based on data from over 36,000 Toyota Prius hybrids in its annual survey, Consumer Reports has found that the Prius consistently gets top marks when it comes to reliability, and also boasts low ownership costs.

But now that the Prius has been around for more than a decade in the U.S., and available on the used-car market, some of those doubters might still wonder what the answers were to their old questions about long-term battery performance, durability and replacement. The same could be said of buyers who are considering buying a used Prius with a lot of miles on it.

The engineers at Consumer Reports recently decided to answer those questions by taking a 2002 Prius with 208,000 miles on it, and putting it through its paces. The magazine's testers hooked the car up to its testing instruments to see if battery performance and fuel efficiency had degraded, and if so, by how much. As part of the evaluation, the engineers also checked into battery replacement costs.

The upshot? They found that there was very little difference in battery performance, fuel economy and acceleration in the used '02 model when compared to a nearly identical 2001 Prius they tested 10 years ago when it was new.

The tests recently conducted on the old '02 model are the same ones they performed on the new '01 model 10 years ago. They drove on their own track, ran it through a city traffic course, and took it out on the freeway.

The detailed results: The '02 Prius with 208,000 miles on it got 40.4 mpg overall, compared to 40.6 mpg for the '01 Prius when it was brand new. Highway fuel economy for the old, used Prius was 48.3 mpg, compared to 48.6 mpg on the new Prius back in '01. And in the city, the numbers were 32.1 mpg compared to 30.5 mpg, respectively. (See chart below.)

Ten Years Old and Still Spry

When it comes to acceleration power, the difference was also negligible – the old used model went from 0 to 30 mph in 4.4 seconds, compared to 4.3 seconds for the new model 10 years ago. And, when the 0-to-60 time was measured, the numbers were 13.1 seconds and 12.7 seconds, respectively.

"Because it was a new technology back in 2000, I think the questions and concerns that people had at the time were understandable, especially when it came to how long the battery would last, and how long the battery would perform at top capacity," says Jake Fisher, a senior automotive engineer at Consumer Reports.

When most people think about batteries, they think about other batteries that don't last very long. Car batteries don't last more than a few years, and anyone who owns a laptop knows how quickly battery life can degrade over time.

"People back then were afraid that, over time, the miles per gallon would drop, it wouldn't run right, or that it wouldn't accelerate as quickly as it did when it was new," said Fisher.

Fisher says he recalls rumors about what it might cost to replace the Prius battery if that was required, with estimates as high as $10,000. But, right now, if the battery on that '02 Prius did need to be replaced, it would cost between $2,200 and $2,600 at a Toyota dealership.

"Except, it's doubtful that anyone would buy a brand-new hybrid battery for an eight-year-old vehicle," observes Fisher. "They would be most likely to go to a salvage yard, and find one on a low-mileage Prius, just like you would if you were looking to replace an engine or a transmission on any older car."

Consumer Reports found many such Prius batteries available at salvage yards in the $500 range.

Prius Taxis Perform

Bradly Berman, founder and editor of HybridCars.com and PluginCars.com, says that he is not surprised by Consumer Reports' test results. "For years, I've been seeing reports from Prius-driving taxi drivers, who have clocked 200,000 miles or more, and they've reported virtually no degradation of the battery or vehicle performance," says Berman. "There have been similar reports on HybridCars.com and other sites from individual long-distance hybrid drivers.

"This is not to say that absolutely no owners of first-generation hybrids have had to replace battery packs," adds Berman. "There have been a few, but my guess is that it's a single percentage point or two. By and large, these hybrid battery packs are way over-engineered. The carmakers were worried about battery longevity, and its potential impact on consumer acceptance, so they went overboard to make sure that the batteries would last longer than any other component of a conventional car."

Fisher and Berman agree that this kind of data should assuage any fears that consumers might have about hybrid technology and its long-range viability.

This chart shows the results of the testing that Consumer Reports engineers recently conducted on a used 2002 Prius, with 208,000 miles, compared to the results of the same tests conducted on a 2001 Prius a decade ago, when it was new.

Toyota Prius Comparison
2001 Prius - 2,000 Miles 2002 Prius - 208,000 Miles
Overall Fuel Economy 40.6 MPG 40.4 MPG
Highway Fuel Economy 48.6 MPG 32.1 MPG
City Fuel Economy 30.5 MPG 46.3 MPG
Trip Fuel Economy 48.5 MPG 46.3 MPG
0-30 MPH Acceleration 4.3 sec 4.4 sec
0-60 MPH Acceleration 12.7 sec 13.1 sec
1/4 Mile Time 19.3 sec 19.4 sec
1/4 Mile Speed 74.6 MPH 73.6 MPH
45-65 MPH Passing 7.0 sec 7.3 sec