Does no climate control give you better mileage

[tomdeimos]

<div class='quotetop'>QUOTE(sethkaufman @ Jan 22 2007, 12:48 AM) [snapback]378880[/snapback]</div>

Hello Prius people. While I have read in the past and it would make sense that turning off the heater and aircon would improve the mileage, I have not seen this. I have been experimenting and see no improvement. I have also read that if you do "vent only" this would also improve the mileage. How in the hell do you do "vent only"? The climate control is based only on the temperature you choose? Is there a button I am missing to bring the outside air in without heating or cooling it. Is "vent only" matching the outside temp w/ my climate control temp?

Thoughts?
[/b]

Very obvious. If I use the heater fully or the ac it often costs me over 10 mpg. You should easily see this too. But there's a couple of exceptions.

1 Turning off AC in summer will save you mpg, except if you are in a climate so hot you either over heat the battery or else you get so hot you open the windows. If windows are open drag increases and if you like to drive up near 100 mph you might lose what you gain.

2 In winter the heater costs you the same way except that if you use no heat and it is very cold the battery will be too cold to operate so you lose there maybe more than you gain. Also if you again like to drive up near 100 mph you may generate excess heat that can run the heater and still keep the catalytic converter hot. Then the heat is essentially free and makes no mpg difference.

For normal conditions and especially shorter trips like under 1/2 hour, heat and AC make a huge difference.
Normally it will be at least 2 mpg and could easily be over 10 mpg. In some traffic jam conditions the cost can be more like 40 mpg.

[sethkaufman]

Hello Prius people. While I have read in the past and it would make sense that turning off the heater and aircon would improve the mileage, I have not seen this. I have been experimenting and see no improvement. I have also read that if you do "vent only" this would also improve the mileage. How in the hell do you do "vent only"? The climate control is based only on the temperature you choose? Is there a button I am missing to bring the outside air in without heating or cooling it. Is "vent only" matching the outside temp w/ my climate control temp?

Thoughts?

[sethkaufman]

<div class='quotetop'>QUOTE(sethkaufman @ Jan 22 2007, 12:48 AM) [snapback]378880[/snapback]</div>

Hello Prius people. While I have read in the past and it would make sense that turning off the heater and aircon would improve the mileage, I have not seen this. I have been experimenting and see no improvement. I have also read that if you do "vent only" this would also improve the mileage. How in the hell do you do "vent only"? The climate control is based only on the temperature you choose? Is there a button I am missing to bring the outside air in without heating or cooling it. Is "vent only" matching the outside temp w/ my climate control temp?

Thoughts?
[/b]

Thanks for the info. I have only been driving in winter. (I have owned the car for only 2 months) and have not been cranking the heater much.

[JimN]

For Gen2 I don't think the AC has much effect on mpg as it is driven by the generator. In the winter, heat (or lack of) makes a BIG difference especially on short trips and the 1st 5 minutes. Some of us block the grill to keep the engine warmer. The colder the engine, the more it runs.

It finally got and stayed cold here. I dropped an average (per MFD) 1.5mpg on two short trips with 200+ miles on the tank. Two 35 mile commuting trips brought it up to -1mpg. I am still showing 50+mpg because of the blocked upper grill. Otherwise I'd be in the high 40's.

At outside temps over 50F I don't think it all makes much of a difference.

[John in LB]

<div class='quotetop'>QUOTE(JimN @ Jan 22 2007, 05:55 PM) [snapback]379258[/snapback]</div>

For Gen2 I don't think the AC has much effect on mpg as it is driven by the generator. In the winter, heat (or lack of) makes a BIG difference especially on short trips and the 1st 5 minutes. Some of us block the grill to keep the engine warmer. The colder the engine, the more it runs.

It finally got and stayed cold here. I dropped an average (per MFD) 1.5mpg on two short trips with 200+ miles on the tank. Two 35 mile commuting trips brought it up to -1mpg. I am still showing 50+mpg because of the blocked upper grill. Otherwise I'd be in the high 40's.

At outside temps over 50F I don't think it all makes much of a difference.
[/b]

I don't have any measurements, but even the Gen 2 AC unit is using power. It actually should be using more power than a regular belt-driven compression system given the conversion from IC to electrical and then back to mechanical work.

Of course, you are taking advantage of the batteries to avoid running the IC, but ultimately the IC has to recharge the electrical system.

I believe the only reason Toyota put in an electrical AC compressor was to avoid forcing the IC engine to come on whenever the compressor was called for. It was not an energy efficiency improvement in its own right.

[JimboK]

My engine temperature, monitored via my ScanGauge, rises noticeably faster on these cold mornings when I leave the heat off. When the ICE is warm, its temperatures quickly drop when I run the heat while sitting still. I've seen it drop 10 degrees or more sitting at a stoplight.

I haven't done an MPG comparison -- with heat versus without -- but it seems clear to me that running the heat at certain times costs fuel economy; the ICE runs more when it's cool. So unless I absolutely need heat for comfort (I bundle up warmly) or to clear fogged windows, I run it only when the ICE is warm and has to run anyway (i.e., accelerating or cruising at 42+ MPH).

[mikepaul]

My Best Ever MPG (Over 10 Miles division) of 58MPG for 64 miles was with the A/C on. Way back with OEM tires, though.

I tend to warm the air in the car then turn the A/C off in winter. Long-term heating does occasionally reach a 10-MPG drop...

[Beryl Octet]

<div class='quotetop'>QUOTE(sethkaufman @ Jan 22 2007, 12:48 AM) [snapback]378880[/snapback]</div>

How in the hell do you do "vent only"? Thoughts?
[/b]

Turn on the AC/Auto, set the temp, bring up the climate display, look for the AC button to toggle AC on or off. When it's off, you are vent-only, at least as far as AC in hot weather. I don't know of a way short of turning the system off to avoid at least some heating in cold weather.

As to thoughts, I thought cabin heat and cooling was also heating and cooling the battery, so that it was better to just get in and drive and not worry about it too much. I do find that on some sunny days with cold temps, 65 is still too hot.