How to Reduce MPG loss Because of A/C Use

When I have a big hill to go down, one that will put the battery gauge up to green and more, I put the A/C to max and really chill things down, thanks to gravity power. Then at the bottom I set it lower again.

 

Good idea!

 

I think Nh7o was describing a condition I also encounter: my home is at 6300 ft elevation, and I often take routes that drop me 1000+ feet in the first five miles. If I coast down the hill the speed is OK, but the traction battery fills to max and then the ICE comes on to waste electric energy. Since that energy is not going to kinetic or chemical energy regardless, I use it for cooling instead.

 

I guess I already use some of the efficient methods discussed in this thread. When my interior is hot, I ride with the windows down to exhaust the hot air and start the cool down of the interior surfaces. Then about 5 minutes into my drive I will turn on the A/C and roll up the windows.

This all goes to the wayside if my wife is with me though. About 30 seconds of cool down and then the A/C is on, windows closed, so that her hair doesn't get fussy!

 

I've had my Prius a couple of months and recently had the 5k service. I saw a big drop in mileage driving to/from Dallas from my home in Houston with bikes on the rear. What had me worried was when I filled up recently and restarted the mileage - 40 or so miles into the new tank I'm getting less than 35 mpg despite my best efforts to go easy. Glad to hear its just the 95 degree temps eating my gas and not something the dealer did. We averaged 47 on the highway across West Texas, NM, AZ and a good bit of desert California and back. Really disappointed til I read this thread to find its just a/c use. I guess it'll get better come October...
I know a lot of you are gonna get another taste of Houston summer in your neck of the woods. Be glad that your mileage is nearly free and you are just paying to run the a/c. I remember my first car only got 4 mpg and had no air conditioner.

 

35 mpg's is not right. Something really wrong there. Unless its all in town stop & go. I use the ac constantly never off and traveling 60 miles an hour get 47 always. Be aware when dealer serviced they deflate the tires to door plate level usually 35 lbs. That will kill mileage. Inflate your tires to 42F-40R. Also make sure you use regular gas also 87 octane only.

 

Those with a Gen II or III Prius need to see the effect of AC on Gen I to know how good they have it. The Gen I had a belt driven AC, requiring the engine run for max AC performance and the compressor had to run at engine speed, not optimum speed. The difference on the Gen I could easily be ~8 MPG. The difference on the Gen II/III would be closer to ~2 MPG for "rational" AC use.

The missing part of the optimization discussion is what to do for thermostatically illiterate AC operators. (e.g. Those that believe AC only has two modes OFF and SPEW ICE......where "on" can only be max fan, lowest temp, and any other setting that uses more gas.) It that case, make the fan run at full speed while sneaking the temp up from 65 to 75.

 

I've gotten in the habit of setting the cabin temp at 75-80F on hot days after I have ventilated the car, but I manually run the fan at a higher power than auto would, and I avoid recirc mode so that more air passes over the traction battery (or so I hope.) I wonder how my AC consumption is compared to a default setting of auto.

Anecdotal MPG readings in my CTh are about 58 mpg from 30 mile trips starting from 90F in the shade, driving at 7pm on country roads at 55 mph.

 

For that route, yes. Overall the last ~ 1500 miles are just under 52 mpg calculated. Not up to my G2 Prius' standards; but as you know better than me, a price is paid for a better suspension and beefier tyres.

 

Yes indeed!! I have only ran the a/c a couple times in my 02. And have found that on open highway i lose about 5-8mpg. In town ice runs non stop and mpg is pretty much non existant.

Wife has already been warned, if you are gonna ride in the prius, dont expect the a/c to be on.

So she chopped her hair and donated it to "locks of love"

 

Don't think I didn't consider it

For now I'll stick with my stock 17 inch wheels, and buy LRR when replacement is needed. If in the future I need winter and non-winter wheel sets, I'll look for 16 inch wheels I can put 205 mm LRR tyres on for the dry season, and stick with 17 inch, 215 mm for better traction in the winter.

 

I can only report my own experiences. I run with AC on 100% of time ... set @ 75 ... here in SW Fla it has averaged 90-92 for past many months and it not unusual to be in the Pri during late morning to early afternoon .... note my miliage below .... I am NOT a hypermiler ... I'm an old GTO guy so I run with any traffic .... sometimes, lead ... :>))

Regards,
radmangto

 

AC use in S. Florida has to contend with humidity, not just heat.