Prius in 100 Degree Heat

Oh Great,

And I have to travel to Atlanta next week. Damn.

 

Move????

Icarus

 

We have driven our 2004 Prius for over four years in the deserts of Arizona and our gas mileage is always about 50 MPG. We use our A/C for about 9 of the 12 months every year. The temperature today is 110 degrees F.

 

must be the dry heat. Over here in the central valley of CA, a.k.a Satan's Butthole because it's hot as hell and in the middle of nowhere, I haven't noticed a drop in mpg. We hit 100 Memorial Day week and last week was pretty much the same.

 

It might knock the average down by 1 or 2 mpg, but remember: your HV battery likes the same kind of temperature that you do, so use that A/C to keep your battery nice and comfy. :madgrin:

 

Joshua,

There is a balance. Back in early May I spoke some rash words about not seeing a FE impact from using the AC. Now that we've started to have our "real" summer weather, I can honestly say that there is a hit that you take for using the AC, however that doesn't mean that you have to choose between discomfort and your FE.

The best thing that I've found for staying comfortable is to prevent the inside of the car from warming up as much as you can. I saw very quickly that I was doing much better on FE on weekdays when I left home before the car warmed up, driving to work where I park under cover. Even when I go out at lunch I was using the AC at a much lower setting than I would normally do on a Saturday or Sunday where the car sat outside in the sun until say noon.

I bought the sun-shade for the front window (yes, it's awkward, but it does help.) I'm saving to get window tint as I've been told that there is also a noticible reduction in heating the inside of the car (and I don't like tinted windows.) I'm even working to get the garage cleaned out so that I can try and get the car in there.

I know it sounds overly simplistic, but the best way I've found to beat the heat is to prevent the car from getting really hot to begin with. You live with this heat so you know that "cool" is relative; it's alot easier to cool off a car that's hot because it's in been parked in the shade vs. cooling one that's been sitting in the sun.

I also know that there's someone on here experimenting with the effects of the dashboard covers.

Best of luck!

 

Last summer when our Prius was new, we were getting around 45-47 mpg, and it was pretty darn hot - we had a record number of 110 degree and above days in a row.

Now I've got 18K miles on her, and she's still getting in the mid 50's - the tank right now is reading 56.8 mpg, and the temps have been in the 100s, yesterday was 112.

I do expect that I'll be down to 54-55 in July and August, as the humidity goes up and it feels yuckier without the a/c. Even now, when I drive in the early morning I can just roll down the windows.

 

None of you live as deep south as I do and I didn't cop that big a hit in Adelaide's record heat wave. Try to drive early in the morning and at night with the windows down as much as you can

 

The good news is that the forecast calls for lower temps this week...back in the 80's!

I'm in Atlanta also but I just got my Prius last week so I haven't had the chance to make comparisons yet. I tried to drive a bit without the AC, but I bailed out of that experiment long before I could see any reults. I've become obsessed already with trying to squeeze more mpgs, but that's where I drew the line.

I'm also a big fan of driving with my window down and I know that won't help the mpg quest, but I've resisted that so far because I want to keep that new car smell trapped in there as long as possible.

 

Under 40 - 50mph windows down is better than AC on.

 

Just got gas yesterday and checked the mileage.... 54.53. Not bad considering our heat and humidity here.

 

I'm also looking forward to getting back in the 80's. October is a great time of year!

 

Here is a similar discussion. I mention in that thread, among other things, the effect of a hot hybrid battery, which this good advice will help prevent:

I didn't mention sunshades, cracking the windows, and window tinting, but they certainly help.

 

Everytime someone from the SouthEast US complains about the MPG impact of AC, a dozen or so people from the desert SouthWest point out that the AC has very little effect on their MPG.

What's missing in these two perspectives is that there is a big difference in relative humidity between the SouthWest and the SouthEast.

In the deserts of Arizona, I would expect that when it's 100+ degrees out, the relative humidity is somewhere around 40%. However, in the SouthEast, when it's 100+ degrees out, the humidity is somewhere around 98%.

At 100+ degrees, there's a huge difference in the moisture content of the air between 40% and 98% relative humidity. The moisture in the air acts like a buffer and it requires a lot more energy to cool humid air 20 degrees than it does to cool arid air.

 

ound: Amen Brother! It was hotter than a popcorn fart in the desert! ound:​

Wildkow

 

I live in the South Carolina low country with my AC set at 73. (my wife loves cold AC--has a bit of polar bear blood, I think). My mileage stays the same 53+/- mpg in our mild winters and hot, humid summers.

 

All I know is that when it hit the upper 90's in Pennsylvania last week, my AC, which is set at 74, would run all out for 15-20 minutes of my 30 minute commute before it would throttle back to a low speed. During that 15-20 minutes, my consumption screen graph bars would be no higher than about 45 and would often be lower than that. The week before, when it was a mere 80 degrees or so, the AC would throttle back in less than 5 minutes and consumption graph bars (after the first one) would be over 50 and as high as 65.

I suppose that if my commute was more like 60 minutes, it wouldn't have as big an effect, but with a 30 minute commute, it drops me from about 52 to around 45. It drops even lower on the weekends, when I don't drive more than 10-15 minutes at a time. That might drop my mileage as low as 40-42.

When running full out, the AC can discharge my battery and force the engine to come on while sitting through one cycle of a traffic light. It is not a small load.

 

Heat affects short trips because it takes a few minutes for the cabin air to cool down the battery system; when the battery system is too hot it throttles itself, and that reduces MPGs. On every long trip I make in Texas summers the fuel economy is fine, 50+ MPG at 65 MPH with the A/C blasting away at 73'F.

 

I guess I have the worst of both humidity and heat. I don't see a difference in mileage during the summer. Last tank was 54.53 MPG.