Anyone know the effect of using a/c on gas mileage?

No free lunch but I use AC all the time in this hot weather and averaging 52 mpg. I'm not a hyper miler, drive normally, 5 mph over speed limit.

It's a smart AC system and the effects of AC are minimal in my experience.

 

The AC compressor is electric, so there's no drag on the ICE. It does however use a LOT of juice and can drain your main battery pretty quick when you're stopped. So it can indirectly effect mileage, which is why ECO mode limits the AC function.

 

Anytime you ask the car to do more work, it'll lower the MPG. However, how much lower will depend on outside temperature, cabin temperature, and the temperature set point. I normally set my temperature to 77 and leave it in "Auto" mode. Since the a/c is powered by the traction battery, you may not see the MPG drop right away. But eventually, the ICE will have to work harder to recharge the battery.

From what I read, the a/c used in the Prius is very energy efficient and has intelligence built in. It isn't like a normal a/c where it's either on or off. The power it consumes will vary based on demand. As the cabin temperature cools down and approach the set point, the a/c will start to reduce power it draws from the battery.

 

June,

For hybrids, think of things this way: all energy comes from gasoline. Even though the a/c compressor is electric, the electricity for it came from the ICE running the generator to put electricity into the battery for the compressor to utilize. Energy that otherwise could have been used by the electric motor to propel the car.

OTOH, plug-in's with larger batteries can make some trips with the a/c on completely in EV mode. If one has a large enough battery reserve, one can make it through the whole day of driving with the a/c on without a gas mileage penalty (infinite mpg).

 

I wanted a Prius for years because of the efficiency of a Hybrid.
BUT....
Some things I just go with. And on Hot Days? I just use the AC and damn the cost!

I could obsess about the minimal MPG loss, but IMO not worth it. On a hot day, I find the comfort of driving with the AC on, is beneficial. I think it makes me obviously more comfortable, therefore able to focus better. It can be a safety issue.

Yes, using your AC lowers your gas mileage. There is no way to bypass the debt. But I'd rather not pay the debt in sweat.

I do however apply thought. If it has cooled down outside and I can be comfortable without the AC? Then I don't absent mindlessly or automatically just turn it on.

 

I just came back from a 10 mile trip using all local roads 35 mile speed limit. Outside temp was 84, I set my a/c to 78 using Auto mode. My MPG was 65 mpg.

I heard that if you put the Prius in ECO mode, the a/c will use less power.

 

Unless you disable this in the vehicle setup, ECO mode lowers the cabin blower speed and decreases the time the compressor runs (hence a higher temp at the coil). It also makes "recirc" the default selection if outside temp is above the low 70's. Normal mode raises the temp threshold for default recirc selection by a few degrees.

I have seen evidence that the ECO mode adjustments lessen the drain on the main batt, but unless you're sitting still a lot it won't impact very much. Cruising down the road it won't matter at all.
I often just reach over and turn off the AC when sitting still, leaving the blower running to pull as much out of the coil as possible. The air output remains coolish for a minute or two, and I turn it back on when I get moving again. This saves a lot of battery energy.

Any manual adjustment of the blower speed cancels the ECO mode control of the A/C.

 

That's what I use to think. Regen energy, either through light braking or coasting, originally came from the ICE running to get the car up to speed or to the top of the hill, etc. Unless you have a plug-in, all energy comes from gasoline.

 

Maaaaybe good for 1 mpg loss in my experience.

 

For any car, A/C is more fuel efficient at highway speeds than rolling down the windows.

Your A/C is also cooling down the batterys, they share the passenger compartment with you, and batteries hate heat.
Keep them cool, they will last longer. And that will be cheaper than the cost of A/C.

Summer Battery Care Tips | Interstate Batteries System of America Inc.

 

Thanks. Good info.

 

Generally I open the windows and turn the AC off when I first start up the car and am going slowly, then turn it on when I get up to speed. But I didn't know that the ECO mode helps so I need to try that.

 

80 Degrees F this AM 46 MPG
95 Degrees F this PM 42 MPG

 

I get better gas mileage in the summer with AC, then I do in the winter with
the heater.

 

It depends. If your car came with the advanced tech package that included a perpetual motion machine, AC is free.

 

Hmm...it probably isn't the heater's fault...the Prius just doesn't like being cold!