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I just filled up the FEH at an E0 fuel station about 40 miles from home. Being in the low 90's today, and I had a passenger - I turned the a/c on. Usually on the trip back home from this station, my dash display usually reads 38-42 MPG by the time I get home. Today with the a/c on, it read 32 when I got home. Does the a/c really take a 6-10 MPG penalty?

Based on experience with other vehicles, that certainly looks about right to me.

My old vehicle got exactly the same mileage, whether or not the a/c was on. This is a big change for me.

My Volvo on the highway is between two and three miles per gallon,or 7% to 9%. The Prius is probably near the same percentages. E-10, AC, and running at the speed limit 25.5 mpg's. E0, no AC and cruise set at a maximum of 65 mph, 29.25 to 29.5 mpg.

In general, other factors being equal, AC would tend to increase consumption by roughly the same amount per hour or per mile for a high-mpg vehicle as for a low-mpg one. Therefore, the difference is much more obvious in the high-mpg one. In the examples above, dropping from 29.5 to 25.5 is about the same added consumption per mile as dropping from 38 to 32 mpg.

That's about the same hit my Elantra took. The Prius, however, is a different beast. If I leave it on "Auto" and set it for something like 78-80F (which is still blowing cold on 90F days), it doesn't really seem to have any mileage hit. My wife, however, prefers to set the fan speed at hurricane gale force AND low temp. THAT has the same hit as what you're seeing ;).

Are these 40 highway miles, therefore non-EV? My experience has been that there is minimal difference in highway MPG using the A/C. But now once I hit the ramp, I would switch to the recirculate A/C, so that I can EV again, because there is no EV when using the Max A/C due to the compressor being ICE based, not electric (like the newer FEHs).

I have found that A/C is a large hit to MPGs when driving under 40 mph, but not really noticeable at higher speeds, so your experience is curious :confused:

It is a highway, but not like an interstate highway. Its a 4 lane road with a median strip, 55 MPH speed limit, and it crosses a couple of mountains. Portions of the road are limited access with exit/entrance ramps, but not all of it. I had the cruise set on 55 MPH, and the a/c set on 75F. Ambient air temp was 90F. Normally when I make this trip, the dash average reads in the upper 30's/low 40's when I get home. This was the first time I made the trip with the a/c on.

In my old pickup truck I even did an experiment one summer to find my MPG penalty. I drove for one week with the a/c on MAX the whole time, if I needed it or not, and the next week I drove with the windows up, a/c off, and vent fan on high. Both tanks yielded the exact same mileage, so over the years I've been conditioned to turn on the a/c whenever I want it.

Is CC a good idea in mountains ?

With a female passenger in the vehicle, yes it is. ;) I don't want to hear complaints that we're being passed by old ladies going up the mountain. Still, I usually show averages on the dash display of about 10 MPG higher than the EPA combined rating by the time I get to the bottom of the mountain. I set the cruise, and go up, then shift to "L" at the top for some aggressive regen on the way down w/o exceeding the speed limit by more than about 5 MPH. The FEH cruise control does rev it high going up the mountain, but it maintains 55 exactly on the way up without falling behind.

I have found that A/C is a large hit to MPGs when driving under 40 mph, but not really noticeable at higher speeds ...
That's logical. To travel a given distance at higher speed, not only is less energy required to power the compressor (because the time is shorter), but also more energy is required to overcome aero drag, so the percentage of total fuel consumption that's used for the compressor will be much lower. However, the additional fuel per unit time to power the compressor wouldn't differ very much.
At very low traffic-jam speeds, operating the compressor will consume more energy than moving the car does.

I don't like to hear female complaints when I'm on a road-trip, either.
That's why she rides in the trunk.

And cruise control in the mountains ? Really ? That's the lazy 20th-Century American's way.

I just filled up the FEH at an E0 fuel station about 40 miles from home. Being in the low 90's today, and I had a passenger - I turned the a/c on. Usually on the trip back home from this station, my dash display usually reads 38-42 MPG by the time I get home. Today with the a/c on, it read 32 when I got home. Does the a/c really take a 6-10 MPG penalty?

My experience has shown at highway speeds it's around a 5% hit on fuel economy to run the A/C. I don't think fan speed matters much but temperature setting will have an impact.

/I suppose both my vehicles would be considered "overpowered",.......a more fuel efficient machine might see a bigger % MPG  penalty for A/C  use. (?)

I don't like to hear female complaints when I'm on a road-trip, either.
That's why she rides in the trunk.

And cruise control in the mountains ? Really ? That's the lazy 20th-Century American's way.

LOL, I am a lazy 20th Century American. I spent $400 a couple years ago tracking down a NOS cruise control unit for my 1981 Buick. For me, if a vehicle has a broken cruise, its almost undriveable.

On long trips I've noticed no loss. my best non-hypermiling tank on my STi (26 MPG) was with AC on the whole time. The same for my Civic Si (years ago) and Fit. The jury is out on the CRZ. I bought it in June and we had a fairly mild summer.

The high outdoor air temp and humidity "bonus" seems to offset the compressor drag by a wide margin.

Also, people misunderstanding how to use their manual climate control settings accounts for a lot of waste I'm sure. a LOT.

Rich wrote:
I just filled up the FEH at an E0 fuel station about 40 miles from home. Being in the low 90's today, and I had a passenger - I turned the a/c on. Usually on the trip back home from this station, my dash display usually reads 38-42 MPG by the time I get home. Today with the a/c on, it read 32 when I got home. Does the a/c really take a 6-10 MPG penalty?
Based on experience with other vehicles, that certainly looks about right to me.
I would have to disagree to a point by 'Right Lane Cruiser' - not that he is wrong but a FEH has a separate a/c unit to cool the HV battery. It uses the same compressor that you used to cool the inside of the car, but it has separate refrigerant lines to a second evaporator in the rear to keep the temp of the HV battery cool. The next is from gpsman1 on GreenHybrid under ScanGauge Data Depository (http://www.greenhybrid.com/discuss/f26/scangauge-data-depository-16100/#post151159):

Originally Posted by gpsman1 in a GreenHybrid post:
The HV Battery will turn on the Air Conditioner if the battery box is warmer than 85'F, but will still allow EV. The HV Battery will run the Air Conditioner full time and dis-allow EV if the battery box is hotter than 100'F.So generally when it is hot the a/c compressor that is taking the extra energy is already running - why not tap into it for the passenger comfort- so therefore 'Right Lane Cruiser' is right pitting it up against a non Hybrid. I don't know which year it was that they went to an electric a/c that you or it could run without starting the ICE.
Now they have even dropped the aux a/c for the HV battery. If you have a ScanGauge II then you can monitor when it calls for the a/c to turn on. The code for that is -

A/C Clutch Commanded On
TXD 07E0221104
RXF 046225110604
RXD 3701
MTH 000100010000
Name A/C

Hi, Phillip -- I was comparing to a broad range of hybrid experience behind the wheel in the Prius, FFH, FEH, HCH (I and II), and the first gen Insight (with plenty of non-hybrid experience as well of course). Some of the above hybrids have electrically operated AC units, but others do not.

I don't know anything about Hybrids, but I've noticed my '97 Escort wagon takes about a 10-15% hit in fuel economy from a/c use. When I'm driving in the mountains of eastern TN. and western NC on I-40 I like to hit the crest of the mountain shift to neutral and let it freewheel down the mountain. I've often seen mileage readings of 300+ mpg on my Scan Gauge on the decents. I know if I left it in gear DFCO would allow for a reading of 9999, but he engine braking takes away a lot from the momentum and speed I can get from coasting. The best mileage I ever got in the '97 wagon was 49.85 MPG on a cool summer morning when a/c wasn't needed and I was driving with driver's side window down and also had the passenger side window down part of the time, I also had the c/c set at 55 MPH, but part of the miles were through the Smokey Mountains. I didn't coast in neutral, just let the c/c do it's job. This was only on a 140 mile fill up to fill up, because the temperature was getting warmer and I wanted to turn on the a/c so I refilled the tank so I could see what it did without the a/c. I knew it was going to be good by gauging from how much the fuel gauge needle had moved. Both times the tank was filled to the cap.

Hi, Phillip -- I was comparing to a broad range of hybrid experience behind the wheel in the Prius, FFH, FEH, HCH (I and II) . . . ..

I guess your response to my remark was taken out of context since I was addressing the original question at the start of the thread from 08EscapeHybrid and since it was posted in the FEH forum and not 'General' - So I was addressing it to a FEH driver - Sorry about that.

I made the same run last night, and I guess all is well. Ambient temps were in the 70's, and when I got home the dash read 44 MPG. The previous tank, which I was afraid had gotten off to a rocky start, ended up being one of my best tanks ever. (Best tank was a battery recal, and this was very close to the 2nd best tank.)

I guess your response to my remark was taken out of context since I was addressing the original question at the start of the thread from 08EscapeHybrid and since it was posted in the FEH forum and not 'General' - So I was addressing it to a FEH driver - Sorry about that.
Yes, you are correct, I originally posted in the FEH forum because I was looking for specifics on a/c use with the FEH, but all input received is greatly appreciated. There was absolutely no a/c mileage penalty on my old DD, so I never gave it a second thought - if I was hot, I turned it on.

My very first DD was a 1965 389 CI 360 HP tri-power GTO without power steering or brakes - I didn't care about fuel economy just being the fastest in town :flag:!!