what percentage does running the a/c decrease mileage and why?

B) The test was conducted with the A/C was set at max with full blower.

When I drove out to California from Nebraska and back it was in August. I set the a/c at 74 degrees and on auto. Drove the speed limit 75 mph and only used a little over 68 gallons of gas on a 3150 mile trip. Which means I averaged 46.3 miles to the gallon and oh yea, the outside temperature was a mere 100 degrees.

You just got to love this car.

 

I couldn't even find where they said it was set on max blower and max cooling. But even with this the % loss will still vary with vehicle speed. There is no one number for everything. And a big % number under max output just means we have good high capacity air conditioners in our cars and says nothing about the true cost in real usage.

I've tested my car quite a bit and I think the number they come up with sounds quite reasonable for some conditions. My worst case is driving home from work where the whole trip is not long enough for the car to cool down the dashboard. My mpg loss in this case could be 20% or worse but depends on traffic speed. If I can maintain 55 mph or better it isn't that bad but could be 10%.

If I go on a trip at 65 mph for reasonable time so the car can cool the cost seems to be more like 3% in mpg.
This with 100 deg F temperatures in sun.

I have also tried testing with AC off and window up vs down, but that effect made no measurable difference I could detect.

So on my commute home I try to leave AC off when I can stand it and open windows. On trips I use AC regularly, but set as warm as I can be comfortable. This helps keep my mpg up. When it is really hot and humid I just give up on good mpg and use AC, or if I have passengers.

Generally I can count on at least 2 more mpg if I can leave AC turned off.

 

(Sorry for a littile OT here.)
<div class='quotetop'>QUOTE(darelldd @ May 14 2006, 04:56 PM) [snapback]255107[/snapback]</div>

My poing is that everything you mentioned above is included in the gasoline cost.
You wrote "the energy for my AC is basically free at this point.", but I believe you'll see shoter driving distance when you use AC.

Anyway, would you please let us know how much did your PV system cost, how much did you pay for the installation, how much do you pay for regular maintenance, how many Wh does the PV system generate, how many years does the PV system last?

Ken@Japan

 

<div class='quotetop'>QUOTE(ken1784 @ May 14 2006, 10:48 PM) [snapback]255552[/snapback]</div>

Ah, that makes sense. I can also make a list of all the expensive stuff that is NOT included in the pump price of gasoline... but was actually trying to find a smooth way OUT of dragging this thread OT.

Yes, my range will be shorter, of course. I think I covered that. I lose about 2-5% of my range with AC on. But NONE of that range comes from gasoline, and none of the power for my AC comes from gasoline.

I paid about $11k for my 2.5kW system (including installation). There is ZERO maintenance (as with almost all PV installations). It is expected to last 30+ years - though I'll likely upgrade the inverter before then, and the panels do fade slowly over time. In 30 years, I'll have offset the equivalent of about half a million gasoline miles if I can manage to keep driving an EV that whole time. If gas stays at ~$3 (ha! Ya think?), that's about, oh..$55,000 worth of gasoline, and 400,000 pounds of C02 if I'm replacing an average US gasoline vehicle.

And again - my point (now lost, and even pathetic when I first brought it up - but hey, it brings me back on topic) is that my AC usage does NOT change my gas mileage in the EV. For reference is this is the line I was was commenting on:

My ONLY point was that NOT every car provides power for the AC via gasoline!

 

<div class='quotetop'>QUOTE(tomdeimos @ May 15 2006, 06:04 AM) [snapback]255378[/snapback]</div>

The test sequences are described in ETA-HTP03.

I think they opened all windows & doors so that those car with smaller cabin would not have an advantage over those with bigger cabin. The A/C load is still based on the test chamber volume and not cabin volume.

Anyway, the test is just for fair comparison between vehicles and not your typical driving conditions. YMMV.

 

<div class='quotetop'>QUOTE(KTPhil @ May 14 2006, 02:04 PM) [snapback]255248[/snapback]</div>

Me too, I drive 300-600 miles a day. While I am cruising at freeway speeds (generally 65mph) I notice about 4mpg loss recorded on the computer. Not sure what they were using to get a 20% loss.

 

Thank you for the great information about your PV system.
<div class='quotetop'>QUOTE(darelldd @ May 15 2006, 04:10 PM) [snapback]255565[/snapback]</div>

I now understand you were saying your EV consumes some electricity, but no gasoline.

Ken@Japan

 

<div class='quotetop'>QUOTE(ken1784 @ May 15 2006, 02:49 AM) [snapback]255577[/snapback]</div>

 

I don't have a Prius yet because my 1998 VW Jetta is running well and averaging 52 mpg. However, by the time I need a new car the USA may well outlaw stinky polluting diesels, leaving me to consider a Prius as a replacement option. One of the ways that VW manages to squeeze over 50 miles from a gallon of fuel is that the motor doesn't use any fuel at all when the engine speed is above 1200 rpm, and the driver's foot is off the accelerator pedal. When the engine speed drops below 1200 rpm fuel is introduced to maintain an idle & prevent stalling. So coasting up to a traffic light in neutral uses more fuel than downshifting through the gears because downshifting is one of the two condtions where the moving vehicle uses no fuel. The other is going downhill (in gear). Gravity keeps the motor turning above 1200 rpm while the driver's foot is off the accelerator pedal, so the engine burns no fuel going down hill. Gravity also turns the AC compressor down hill. So when driving in the mountains, I switch the AC off going down hill and on going uphill and the car cools off for free. Unfortuately, this technique doesn't work on well flat terrain.

 

Hi all, I've noticed the mileage in my prius going down as the weather gets warmer in Milwaukee.

I use it (still need a name) for work, so I'm in and out of it all day long. I don't crank the ac, but I do have it on. Sounds like I'm better off lowering the windows, or at least spending a couple of bucks for a sun shade.

 

<div class='quotetop'>QUOTE(beermandave @ Jun 7 2006, 06:16 PM) [snapback]267545[/snapback]</div>

I live 26 miles south of you. In January I was getting around 46mpg. Now, in June I am getting 53.9mpg. I use AC when it's hot outside. But you shouldn't be noticing a drop when the weather gets warmer. Just the opposite. Something doesn't add up.

 

Well, I usually do not use A/C since my office is around 60 deg so my commute home I try to absorb all the heat to warm back up. However, when I have guests like today I use A/C. My MPG went from 67.3 to 66.2 just going 18 miles with the A/C on in 102 deg temp on flat roads (tank is at 318 miles so it does not shift much). hahaha I had to chide myself about getting angry with the drop in my possible all time high score on the buiilt-in Consumption computer game.

I am not sure why either. Could it be the road heats up the tires, making them more full? In the morning my psi is around 41. When I go home in 102 heat they are around 45 psi. oh also they switch to summer gas (no ethonal).