Your a/c vs fuel efficiency?

AC uses a lot of power. This is normal. You need to pick the best compromise that fits you.
The ac has to go at full output to cool the car down on short trips if you let it and that uses lots of power.
The heat stored in the car can take close to a half hour to stabilize.

Same concept with refrigerators. I just go a new one and they said don't put food in it for 24 hours so it has time to cool.

You are getting a bigger hit than most people do at 90 degrees maybe. But all you can do is use less ac if you want more mpg.

1 Park in the shade.
2 Get window tinting if you can.
3 Use sun shields when you park and leave windows open when possible when parked.
4 Aim cold air vents directly at you so you can be resonably comfortable while not even trying to get the car dash etc cooled off.
5 Take longer trips so the car can stabilize and ac load goes down to normal.
6 Run fan on lowest speed you can handle.
7 Open all windows when starting out for a few minutes to get car down to ambient temp before turning on the ac. and closing windows.
8 Keep in mind your actual mpg heads down to 0 when you are stopped. So your mpg hit will likely be less when you can drive faster. For my 2005 Prius I generally find I can keep the mpg loss to 2 mpg or less if I drive 60 mph. Drive at 30 mph and it will be 4 mpg etc. (This is on trips when car has time to cool)
On short trips with a hot car that was parked in the sun I can often lose 10 mpg.
9 Get a white car next time, if yours is some other color.
10 Remember the better your AC the worse the mpg hit, unless you cut the output. My last car had almost no ac hit in my commuting, because the car had to run AC full blast all the time and on my short commute it just never was able to cool the car down. With Prius AC I can burn about as much gas as I want to be as cool as I want to be.
11 One extra thing I did was add sound insulation to the doors. I did it more for AC heat insulation than for sound deadening, and it does help noticably. Helps with keeping warm in winter too. So this year I can use less AC power and still be comfortable.

 

<div class='quotetop'>QUOTE(Leslie @ May 26 2006, 08:12 PM) [snapback]261241[/snapback]</div>

Following is a good article by Denso...
http://www.epa.gov/cppd/Presentations/Mats...%20inverter.pdf
On page-7, it says the 2004 Prius AC is 19% less impact for mpg than the previous model.

Ken@Japan

 

<div class='quotetop'>QUOTE(tomdeimos @ May 26 2006, 04:58 AM) [snapback]261257[/snapback]</div>

Most of the solar radiation enters the car through the windows. The body of the car is insulated. I don't believe the exterior color of the car makes a significant difference. A black car will have a hotter exterior skin temperature, but the amount of that heat transmitted through the body to the interior will not be great.

 

another benefit of living here. summers are relatively mild. also not driving during the hot part of the day will help. prime examples (some of the result will be mitigated by break-in and changes in technique)

2004 one of hottest summers on record. 54 mpg work hours 6 am - 2:30 pm. A/C most days. driving home during hot part of the day. speeds only 35 mph

2005 normal summer 58.5 mpg. work hours 10 am to 7 pm missing the hot part of the day rolling down windows on ride home sufficient for most days.

this summer, will be working 6 am to 5 pm so will be leaving at THE hottest part of the day. (sun sets after 10 pm here in summer) so will be hard to not use air. but will try to as much as possible. either way, averaging 56 mpg is what i expect to do.

 

Almost all my best reported MPGs were with the A/C on. How sticky the tires are has always made more difference.

I'm trying my best to extend the fan life by only using heat or cooling when I'm uncomfortable, but that probably ends for the season this weekend when every moment I'll be in the car, it will be too hot to go without.

Maybe by November, I could go without some cooling...

 

I know this kind of sounds harsh. Try 78- 80 degrees with auto ac on. I know for me I don’t even use the ac utile it’s over 80 with the humidity around here u cant go much over 80 without suffering. However, the ac takes care of the humidity so 80 isn’t to bad. :mellow:

My biggest complaint is that when people ride with me as soon as they see sunlight they want the ac on max cool all the time :angry: :angry:

 

<div class='quotetop'>QUOTE(daniel @ May 26 2006, 09:00 AM) [snapback]261264[/snapback]</div>

I disagree strongly with this statement. I had a black car previous to the Prius and I will never own another one even though I like the color. My Prius is not white, and also has more window area but is much cooler when I get into it than my old car was when I park in the sun on a hot day.

I do agree while driving most heat comes in the glass area, but parked and using a sun shade, a big part of the heat is through the body of the car. I have melted plastic in my trunk in the black car, and just testing cars trunks in the parking lot a work I found thw white ones were noticably many degrees cooler.

Keep in mind here we are talking about short trips. On a long trip the AC load decreases to a reasonable level, and fan speed goes down to a low speed, but on my commute it doesn't get much below full output unless I limit it. I have often lost way more than 10 mpg due to AC during commutes, but on trips I rarely lose more than 2 mpg. from AC use.

 

have to side with Mike on this one. i lived in the south enough to know that driving without A/C simply aint an option no matter what color the car. just the tradeoffs you have living just about anywhere. you will get it back this winter when im doing 45 mpg and you are still at 50

 

Maine isn't exactly noted for requiring a/c, but I minimize the use by allowing the cabin to maintain a higher overall temperature than I would otherwise like, and maximize our comfort by directing the cooling air streams directly onto us. Very rare that we ever have anyone in the rear but if we did we'd have to do it differently. We also use the suction cup window shades to reduce direct sun shining onto us. One can see through them, so they aren't a driving hazard.

 

I've been tracking mileage vs temperature and you can see from the graph on the lower part of this page that A/C does start to affect mileage as the temp goes up - Paul' Prius

I've done some testing of car external temperature vs color - Ext Color vs Temp

I did some tests of window shade screens and window cracks to show the effect on interior temperature when parked - Variable Interior Temp

Now that my wife also has a Prius that is a lighter color I'm going to test the interior temperature vs. exterior color. I suspect the greenhouse effect through the windows overpowers exterior car color, but we'll wait for the data.

 

<div class='quotetop'>QUOTE(IAO @ May 26 2006, 12:30 PM) [snapback]261374[/snapback]</div>

It's hot here in MO already, 92 today. Today, I set the auto A/C temp to 78, cooled the car just fine, fan speed low, and didn't notice any noticeable hit on my in-town, stop and go shopping.

I always drive for the first 5-10 minutes with all the windows open to lower the internal temperature of the car.

I did notice the battery drain down to two bars today for the first time. Freaked my wife out but I told her to be calm, Pri knows what she's doing (it's a girl). Battery level came back up after driving her for 10 minutes or so.

 

VW ran some tests a few years back in Arizona on two identical cars, one black, one white. After 8 hrs in the sun, the interior of the black car was 50 degrees hotter than the white car.

 

<div class='quotetop'>QUOTE(Leslie @ May 26 2006, 07:12 AM) [snapback]261241[/snapback]</div>

Yesterday I used the AC for the first time. It was 83 degreesF and very humid. First I opened the windows and drove for 1 mile, next I shut the windows turned on the AC with the temp set to 76, I made sure the air was set to recirculate the air in the cabin rather than cool air from outside. As soon as I was comfortable I turned off the AC (about 3 miles after turning it on). I then increased the fan to just under medium, kept the air recirculating in the cabin, and drove home fairly comfortable with the air directed up (heat rises, cold air sinks) for the next 28 miles. I also get sore throats from fan air directed at my face so I rarely do that. My MPG hit for the trip was negligible.

 

IAO must be made of tougher (not to mention cooler) stuff than I am. With the sun shining through the glass, I would just melt if I kept the thermostat on 80. I consider myself a martyr tolerating a setting of 72 on sunny days. :lol:

 

Hello from Japan,

We, in Japan, have following solar powered ventilation system while parking.
http://www.netprice.co.jp/netprice/library/goods/119651/
http://www.e-zaurus.jp/pitem/65204570
Is there one in the States?

Ken@Japan

 

I'm seeing a 10 - 15% hit on FE (from 68 - 73, to 55 - 62) in my high desert (hot, sunny, very low humidity) climate when the temps are in the low 90's.

Tint has helped a LOT, in making an 80 F setting on the thermostat quite reasonable. New Mexico allows 30% max tint, one of the most lenient in the country.

I'll do just about anything for shade
Windows open a crack when car is parked.
I keep the cloth cover extended in the hatch area, mostly to provide shade for the battery.
Front window shade, even if I stop for a few minutes.
Windows down, AC off for the first couple of minutes after parking.
Then AC 80F, fan high.
I'm trying to get into the habit of leaving the house with a cup of ice water. Cooling just me is smarter than cooling the entire car.
I've also occasionally watered the car at home to allow evaporative cooling five minutes before driving off.

Daniel: I lived in sunny very hot and humid Israel when car AC was unheard of. It was uncommon to see anything but white cars. Now that AC is in cars, darker color cars abound.

 

<div class='quotetop'>QUOTE(ken1784 @ May 27 2006, 10:11 AM) [snapback]261750[/snapback]</div>

Ken, I bought something similar here once for my last car. It did not work well because the solar cells were designed to go inside the window and the tint was enough on the side windows to make it get very little power.
I still have it and plan to add a remote solar battery for it someday.

For the prius I think it might be good to just crack the windows, and put a solar battery on the roof to directly feed the battery blower. Anybody tried that yet?



One thing I added to the Prius is two sun shields. I have the roll up one from here that I use when I park at work but I also got a less effective one that is on the edge of the window and just stretches across so is always ready to use and takes a half a second to open or close. I use this one when I am parking for a minute to go into a store.