Summer is here 35 mpg :(

Tint will help -- direct sunshine into the car is an extra load your AC has to deal with, and the sunshine on your skin makes you want to drop the thermostat. I am tolerably comfortable at 80F (26C) unless the drive is over an hour.

The more effort you put into keeping the car cooler while parked will pay off handsomely:

• Walk for shade
• Use a sun-shield
• Crack open the windows. You can buy rain-guards if needed in BC

If the cabin is substantially hotter than ambient when you get into the car, first drive for 5 minutes with all the windows down, then close up and use AC.

Given a chance, the Prius (including the vagon) loves hot weather. I am getting 60 mpg these days in mixed rural/highway driving.

 

Try ECO mode, but I doubt that the A/C is the cause of your low mileage.

 

SageBrush has the right ideas on conserving gas during AC months. My 2012 Prius V (5) is very cool inside when the temperature setting is at 80. I thought that would be too warm, but it is very cool when set at 80.

Jack

 

The A/C does not have any direct impact on mileage. It does slow the rate at which your battery charges, and in stop-n-go traffic your battery will run lower. But unless the ICE is turning on regularly just to charge the battery, the A/C isn't hurting your mileage. You can also just reach over and punch the A/C button at stoplights and leave it off for a minute with the blower running. It's true that the ICE might run a bit more when the battery is less than 50%, but its an indirect effect of using A/C. ECO mode will reduce that effect. Adjusting your driving practice so that you're getting more regenerative charge will eliminate the issue and also increase the gas mileage too.

But your 35MPG "problem" is more likely due to terrain and driving habits than to the use of the A/C. Heavy use of the A/C *might* cost you 1-2 MPG at most.

 

AC uses energy. That energy is drawn from combustion of petrol. The power draw IIRC can be as low as 150 watts or so, or as high as 3 kW. The traction battery in the middle of the power flow lets you time shift the fuel combustion use a little, but the power drain is what it is.

City driving takes some 4 - 7 kW, so AC can add as little as 7.15/7 to as much as 7/4 to energy consumption. As you can see, the amount of AC used can affect fuel economy greatly.

E.g., this national lab Prius study found that fuel economy dropped from 53 mpg on the SC03 test cycle to 37 mpg when AC was added.

 

I'm using a/c full time now with the heat and humidity. I'm finding I get the best mileage if I can start with as full battery charge as possible, but sometimes that's not possible. Being a realtor and carting people around the community I work in drains the battery quickly to the point I'm at two bars, so the ICE will run to keep it charged. Then heading home, the ICE is pulling double duty to charge the battery and provide enough juice to keep the a/c blowing. If I have a slow day and have a full battery, mpg's is significantly higher from the start. I hate to see when I'm doing 50-55 mph, I'm only getting 35 mpg, but on a full battery I should be at 50+ mpg.

 

Cannot understand avg 35mpg? I am in temps bumping 100F, under ac load and stop and go...but still avg 46+mpg. I do hypermile every chance I get, but drive normally otherwise. Rolling terrain. Did you check your tires lately? Mine are 1# over recommended. Low air in tires will certainly eat up mpg's quick.

 

Ditto. Odds are good that the OP's issue is caused by a combination of factors, with the use of A/C being near the middle or bottom of the list.

 

If you ever want to see AC really become an energy pig, turn it on in a high humidity environment. E.g, I think the power draw approaches 5 kW for defrost in the winter.

 

Overuse of AC is absolutely a MPG killer! If you can, turn it off! I never use AC, I just crack a window!
8gal = 400 miles in summer!

 

If you are cooling down your car multiple times a day that will assuredly explain the drop in fuel economy. As I said earlier, look for shade, use aluminium sunblocks, and try to keep the windows cracked open for ventilation while the car sits.

 

On the last Marathon with a VW Passat TDI where Wayne Gerdes and Bob Winger achieved about 78 mpg said they just cracked open the windows only about 1/2 inch to 1 inch for ventilation - they only turned on the AC (cranked up to the max) when going downhill or just opened up the windows after the vehicle had stopped. Most hypermilers will *pulse* their AC on at max and then shut it off until it gets really hot. ECO mode on the Prius attempts to automatically limit the Air Conditioner's load - so if you have the Air conditioner on all the time ECO mode will help limit its effect on fuel efficiency.

It's getting quite warm here in the DC metro area and my mileage is starting to improve with the drier weather.

 

While not using a/c during the summer is great for hypermilers, sitting in a hot car, sweating, especially on the way to work, is not for me. Neither is driving especially slow, which quite frankly is obnoxious to other drivers on the same road. I can't imagine making an 8,000 mile road trip with no a/c during the summer. Temps for my morning commute is already in the 80's and we have our typically high humidity, so the a/c is working overtime to keep things cool. Fortunately, I have garage to park in and mornings are not as bad as the afternoon commute after sitting in the parking lot all day - no trees. My recent window tint job has helped.

 

In summer, I blast the AC, the music, and drive aggressively (but safely ), with my HIDs on daytime. I also only drive 9 miles to work, so my engine is rarely warmed up. My car is black with tints and solar roof; it does get hot. As a result, I also average 35mpg. But that's a lot better than most any ICE-only car driven exactly the same way, that's for sure! And if we ever have gas lines, i can still kill the AC and hypermile with the best of them. But as long as there is plenty of gas and i'm in the the most fuel efficient car, AC will be keeping me nice and cool...while I speed around town! With zero guilt.

Before my first prius (I'm on #3), i had a Saab 900 which I drove the same way. 18mpg. So I'm doubling my MPG even if i am nowhere near the EPA rating, and I am 100% satisfied with that. My Saab had terrible AC on top of it all, and was stone age compared to the tech in my 2013 prius. Huge improvement all around.

 

Peakciv, I hear you about driving more for pleasure versus peak mileage. But I feel guilty if I do it!

 

mid to high 90's here, don't drive the car special in any way, still averaging low 40s