I can't be the only one... right?

Uh, no. In that temperature, I'd definitely be using ac. Lots.

 

Well, my wife doesn't suffer in the heat. She's ready to use A/C on LO because she doesn't like lots of fan blowing. Auto's propensity to blow the fan hard means it never gets used.

However, unless ambient with the breeze of motion is hot we'll have windows open at lower speeds and the A/C off.

She also won't suffer in the cold. The heat will be on HI to heat up the car as quickly as possible and then she'll lower the temperature. Unless she gets a hot flash in which case the heat will go down for a few minutes.

If we're together I'll gradually be lowering the temperature during the trip.

I'll suffer in the 70s or crack the windows at <=55mph but once it gets to the 80s and I can't crack the window to get a cool breeze through the car I'll use Auto at 72.

I'll suffer in the cold. As long as the windows don't fog up, I'm fine, so the heat gets toggled a lot.

 

I got my Prius right at the very end of May. St.Louis gets hot and muggy and if the weather is pleasant I'll be on my motorcycle anyway. If I got air, and it is hot it's running. I leave mine on auto, never had that fancy option before. I only have 2,000 miles on the clock, so far I have stayed above 45 but not cracked 50 mpg. I don't go too overboard for mpg's but I'm gliding more and have made some adjustment to my driving style, I'd be happy with a solid 50

 

I don't see any effect of AC on MPG, but I set the AC a couple of degrees below outside temp and recirculate. That gets me most of the comfort from dehumidification without the refrigeration. That's in 80-90F weather around here, not sure what I would do in hotter conditions. I was in the hospital during the only spell of 100F weather we had in this area this summer.

Not quantitative because it's difficult to run back-to-back tests over good long distances without conditions changing (wind, exactly how I drive).

But I suspect (a) harder use of AC may have a bigger impact on MPG and (b) driving style may also have something to do with it.

Incredible that people survived without AC in cars until the '70's. Hardy folk.

 

8 months ago you would have been in winter so your MPG would have been less than in Summer. So please update us on your winter mpg as continue with your current practices. It would be interesting to compare it to last year's efforts.

 

In my experience that is why you are not heavily affected by AC use. Setting the temp for 72deg or max cold is what hurts MPG because the car takes a very long time to cool down to those temperatures and thus runs the compressor too hard. When I run the AC at 5am and temps are in the 70s the compressor doesn't come on at high speed and the mpg drop is very minimal. If I do the same test on the way home when temps are in the 90s or 100s the drop is 10mpg and didn't come back even after approx. 10minutes of driving. Someday I will test it for longer than 10mins and see how the drop relates to outside temps vs. inside temps.

Watch

 

Six years of driving a Prius hasn't changed a whole lot about either my desire for high mileage or comfort in my car. In the days before A/C, the only choice was to put the windows down. There was a noticeable loss in MPGs doing it in the 70s, just as there is today. When I'm driving around town and the interior of the car isn't too hot, I'll put the windows down. This isn't just to maximize MPGs, but because I like it. When I'm on the highway, regardless of the temps outside, the windows are closed and I have AUTO on, with A/C during the summer months. I set the temp at 74 and drive.

Early on in my Prius days, I eschewed the AUTO setting and sometimes even the A/C, hoping to get higher MPGs. I know I did get better gas mileage, but I was uncomfortable at times -- especially when wearing a suit and tie in the summer! I'm much more interested in driving for comfort now, though I'm always trying to get a more economical ride. Lifetime mileage is still above 50, with late Spring and early Fall giving me the best mileage. Winter is an absolute killer on mileage, and Summer always causes a dip (due to AUTO A/C at 74). But I'm pretty happy with the car!

 

My pleasure. it really doesn't change the need to take care of the HV battery and your sanity by staying cool but I wanted to present facts so we can make the best decisions or at least know why our mpg may be lower than expected.

 

I run the A/C all the time in our summer heat. So far in my first week with a 2010 II, I've gotten averages between 50 and 60 MPG. It's all about knowing the car - inflate tires to 42/40, use Pulse/Glide when possible, avoid hard accelerations and decelerations, draft in traffic when you see opportunities, and always pay attention to traffic 1-2 blocks ahead if you can so you can get a smooth regenerative brake charge.

If you don't crank the A/C and heater, driving smart should completely offset their effect on MPG.

 

I got my new Prius in May. I traded my old Prius on a brand new Prius. I do not yet have 4k miles on it. It seems to be getting better mileage now than in the beginning. I guess it makes sense that it would improve as the engine begins to break-in.

 

Please correct me if I am wrong but by the looks of the dash in your video, your test was not conducted on a gen III Prius. The gen III Prius does not run the a/c compressor directly off the ICE as previous gen Prius did. The immediate change in MPG seems to be from a/c compressor turning on. Since the compressor on the gen III prius runs directly from an electric motor, I would assume that the MPG change would not be so immediate since there is no mechanical connection to the ICE. The A/C unit in the gen III would be more efficiant than previous gen Prius.

 

There is no free lunch. Running any electronics on the Gen III Prius consumes energy. The only way to generate energy is with the ICE running, and regenerative braking to a lesser extent. So if you want better milage, turn off all your electrical accessories/necessities.

 

The change occurs on the GenIII as well but it appears to be a couple mpg less of a hit initially. I was able to watch the nearly instantaneous mpg drop in my 2012 as well.

 

The gen II uses an electric compressor as well. The change you're thinking of is the water pump - run off accessory belt to ICE on gen II, all-electric on gen III.

 

just want to add as well that I use the AC whenever it's hot outside. I bought the car back in late June and until last week have had the A/C on constantly due to heat. we've had a little break in temperatures lately (this morning it was below 60F when I left for work).

Usually leave the A/C on and auto set at 79F, a little lower if it's above 100F outside. Lots of hills here so A/C is the least of my problems - happy to be averaging more than 44MPG.

 

a/c also runs in winter. Otherwise, in most situations, you wouldnt have the ability to defrost or defog your window in the winter.

 

I bought my V last November. So, I got a chance to experince a full PNW winter with it. Even with the cool and very wet winter we get, I never needed to use the A/C to dehumidify the car. Just heat alone was sufficient here in the NW. I guess it depends on where you live.

With regards to A/C hit on mpg on the GenIII, I noticed the hit is half or less than the video showed. We drove our V (essentially a 300 lbs heavier GenIII) from the PNW to Yellowstone NP and back. We used A/C for all but the driving within the park and still managed 48 mpg (even with the overall elevation gains). In my opinion, driving speed is a bigger variable than A/C use.