A/C draw

same here. it's extremely efficient and hardly noticeable in mpg's.

 

i'm in socal and i have been averaging 41 with the AC always on at the lowest setting. i am not sure what i am doing wrong, but another member convinced me its the Bridgestone Turanzas i am currently sitting on. any suggestions? i was really hoping to get more than my GenII (about 42 averaged over seven years) but so far i am getting less...

 

Check Air pressure in your tires? Air conditioning fan speed set as low as you can live with.

 

I've been using the AC with fan on low for the last month in my PIP in EV mode. I haven't noticed any difference in EV mileage. Wouldn't have believed it.

 

are they lrr? tyres can be a hit to mpg's.

 

Are you driving up and down those fabulous socal hills? That might explain it.

 

JANSone, depending on what you mean by "lowest setting", that may be your problem; what's the temperature set at? Do you mean the lowest fan speed, the lowest (coldest) temperature, or something else?

The most efficient way to run the A/C in the Prius is to let Auto do its thing. If you want to have the fan running slowly, adjust the temperature until the fan is running at the speed you want, while remaining in auto.

The reason is this; the compressor is what's using most of the power in the system. The fan uses maybe a hundred watts or slightly more when at top speed, and a fairly negligible amount at lower speeds; however, the compressor can use several thousand watts (I'm pretty sure I've seen 4 or 5 kW, maybe more). From what I've seen, it appears that the temperature setting is what controls the compressor; so if you have the temperature set to 68 and the cabin is 78, then the compressor is running really hard to get the temperature to 68. However, since the fan is running slowly, only a little bit of air is actually doing the cooling for you. It's quite a bit more efficient to run lots of hot air through the evaporator coils and cool a lot of air by just a little bit, rather than to cool a little bit of air by many degrees.

That said, the A/C alone probably isn't responsible for your fuel economy. Some of it may be the traffic and routes that you take. Some of it may be your driving style (try looking further ahead; if you see a red light or stopped traffic, start coasting now, and don't wait until the guy in front of you brakes). And yes, some of it could be your tires (you can always try inflating above the pressure on the driver's door jamb, but stay below the rating printed on the tire's sidewall for safety - this trades some comfort and noise for fuel economy, should you so desire).

 

thanks for all the help. i do keep my AC at "LO" and the fan is usually at the lowest setting, so i will try raising my temperature a bit to see if that helps. i also have Bridgestone Turanzas which i think came from the factory and have read horror stories about on PC. i also have to factor in my 17" pkg 5 wheels that weigh a couple dozen lbs a piece, and the fact most of my driving is with my wife, two kids, stroller, etc. thanks for all the tips, i will update after my next fillup and see if any of this helps...

 

I set my Air cond. kind of like this, if 95 degrees out side I try setting the temp at 90 degrees if that is still to hot then I try 85 if still to hot I try 80. The closer you can stay to the outside temperature the better. This way the compressor runs as little as possible. With my wife she has to have it 75 dergrees, freeze me right out. Thank goodness she usually does not ride with me so I can set the temp at about 5-10 degrees cooler than outside temp.

 

So as long as the AC is on, the air coming out will be cool? Won't the air coming out be 85 or 80 degrees if u set it to that?

 

You know, I do not really know. I think it trys to maintain your cabin temp. with a combination of fan speed and comperssor running. Hopefully someone smart in air conditioning will chime in and help us out!

 

No. The temp setting is simply telling the compressor to run or not run based on the temp of the coils. Its really no different than the old systems with the red and blue slider, they just gave it a digital control and added numbers. If you're using auto mode, it's similarly controlling the blower speed based on the temp in the cabin.

FWIW, the average A/C system can deliver air that's ~40' cooler than the intake air if the compressor runs at max. The bigger the compressor and coils, the more heat it can remove from the air.

 

Thanks!

 

after reading this post a half dozen times, i think i understand...

i need to set the AC to auto, and then set the temp basically as high as i can tolerate it, that way the components of the cooling system will not be working as hard as when i set it to "LO"?

if not i need to go back and read it again haha thanks for all the tips though, its really frustrating to me that i am not getting 45 like i did in my GenII

 

Correct! Then the car will adjust the fan speed as needed and the compressor will run as needed.

 

it worked. it was 90 when i went to lunch, and i kept the AC on auto at 85 and the air coming out was nice and cool. thanks for everything, i will update on the mileage after i take a 100 mile drive tonight...