Toyota prius

We are considering purchasing a Prius, but before we do, I have two questions about the car. As background,We live in Houston, TX where A/C is a necessity and is used constantly. Also, most of our driving is on surface streets at speeds of less than 40 mph. My questions are:(1)In the Prius, is the A/C unit driven by the gasoline or electric motor? If it is the gasoline motor, how fuel efficient and environmentally friendly is the Prius under such Conditions? (2)How long does a Prius battery typically last before having to be replaced? Thank you, Don

I am not sure exactly how the A/C is powered, but it has not been a problem. Your driving conditions sound like a good candidate for a hybrid.

No one really has a good idea of the battery life so far and that is good because it means the batteries are showing good life in the existing cars.  

 How ever I will suggest that few people off any hybrid car are getting the EPA estimated mileage or better.  The problem has been bad enough that the EPA (or whoever does the testing) has a new test which should give more realistic results for next year.  Note: none hybrids also have been falling short of their estimated numbers but not as far.

In the hybrids, the A/C compressor usually runs from the high voltage battery.

The AC is electrically driven and works very well. As for mileage, it is actually better in city driving than at high speed. I get 52 mpg all around, but in city driving, I get 57. Mine is an '07.

The EPA does the testing and issues the mileage ratings. They have revised the ratings downward on ALL cars.

The battery is warranteed for 8 years or 100,000 miles. The same battery is covered for 10 years in California. There are taxis in large cities that are over 240,000 miles on the original battery.

For a wealth of Prius info, there is a dedicated forum at

Hybrid cars are very efficient for stop and go, city driving. If you are averaging less than 40 miles/hr, Prius will give you decent gas mileage in the range of about 50 mpg. Using the AC will reduce your average gas mileage on hot days. If you are able to manage by setting the AC temperature two degrees below outside temperature, you will get the most mileage. However, when it is very hot outside, it is not always practical to do so.

The Prius battery has a 8 year/100,000 miles warranty, though it is expected to last over 150,000 miles.

You’re a great candidate for the Prius. Since the engine has to shut off, I don’t see how the AC can be solely operated by the engine.

Thanks to everyone who responded. You’ve help resolve the concerns I had about operating a Prius in city traffic in Houston.


On the NHW11 2001-2003 “Classic” Prius sedan, the AC compressor is directly powered by a belt off of the gasoline engine. For the AC compressor to run, the gasoline engine will also run. (So, in the heat of summer, the engine may come on more often than otherwise just to power the AC compressor.) However, unless you have the front windshield defroster/defogger position selected or the MAX AC button pressed, the AC compressor does not run full-time/constantly (the ICE always on). The AC compressor may be used if you have the AC button on, but not always. If at a stoplight, for example, and the cabin is already at/near the desired cool temperature, the ICE will still shut down, and the fans will continue to blow the remaining cold air into the cabin. When the air being blown into the cabin or the cabin itself gets too warm, the ICE may turn on (even while the car is stopped/idle) just to power the AC compressor. The AC compressor/ICE will cycle on/off as needed to maintain the coolness of the cabin.

On the NHW20 2004-current Prius hatchback, the AC compressor is electrically driven by power from the hybrid traction battery. So, the gasoline engine is not required to power the AC compressor. However, should the charge of the hybrid traction battery become too low (say from a long time stopped while the AC is on), the gasoline engine will be restarted just to recharge the battery. But the ICE use is independent of the AC.

You may be interested in checking into some local groups:

The hybrid battery is fully warrantied in the US (NOT pro-rated) for 8 years/100,000 miles. (I don’t think that TX is a CA-emissions state. The NHW20’s hybrid battery is further covered out to 10 years/150,000 miles under the CA emissions warranty in those states that have adopted the CA emission standards.) Hybrid battery replacements are very rare, so NOBODY can tell you how long they should last.

Quoting from a June 22, 2004 Toyota press release:

How long does the Prius battery last and what is the replacement cost?

The Prius battery (and the battery-power management system) has been designed to maximize battery life. In part this is done by keeping the battery at an optimum charge level - never fully draining it and never fully recharging it. As a result, the Prius battery leads a pretty easy life. We have lab data showing the equivalent of 180,000 miles with no deterioration and expect it to last the life of the vehicle. …

There are also several hybrid taxis that have gone over 200,000 miles now, along with several individual owners reporting similar high mileage and no hybrid battery problems.

Oh, and I’ll note that the EPA doesn’t do the testing (only does a random sampling each year to check compliance), but outlines the test procedures and mathematical computations - each manufacturer does the testing and provides the test reports to the EPA. ALL cars are having their reported fuel economy revised downward for 2008 (web site has adjustements up now for older model years for comparisons), to better reflect Americans’ changing driving habits. Too bad the new numbers aren’t used for CAFE fines…