Windows down or A/C on?

I don't notice much difference with ac on lower settings. Higher settings will decrease your mpg

SM-N900P ?

 

I open the windows to get the heat out & then run with the AC. Do not worry about the MPG. Staying cool is worth it.

 

In city driving if you prefer the windows down, leave them down, on the highway, windows up.

 

On a HOT day, let your windows down to let the HOT air out of your car; when you first get in. You can drive with your windows down will also help. This will help your A/C to COOL down faster, after you put your windows up.

I turn my A/C on outside air with windows down; then later I put A/C on inside air, with windows up.

 

On a hot summer afternoon before I start my commute home, I open up the car door(s) and even the back hatch to let the hot air escape for a minute or two and let the cabin vent out a bit before entering the car. Parking in the shade can help keep the car cool in the summer too. During the first few minutes of my commute home from work - I'm only driving about 7-15 mph out of the garage and about 15-25 mph in the city so having the windows down instead of having the air conditioner on works fine to get the cabin cool down for the first 6 minutes of driving from a cold start. My commute home out of the city is basically going uphill(+300 feet elevation over 16 miles) - with the first 15 to 30 minutes often in bumper-to-bumper traffic with a few aggressive drivers weaving in and out of multiple lane fighting to get one car length ahead of everyone else. During the first 15-30 minutes of my commute finding opportunities to hypermile is more challenging and driving safety is more important than fuel efficiency. As I get out of the city area and if I'm able to drive over 35 mph and I can physically handle it - I'll roll up the windows to get better fuel efficiency. However, if the driving temperature get really hot and/or I'm physically tired - I'll roll up the windows and turn on the climate control just to make driving less physically draining and to increase my driving acuity. Driving safety always comes first. Climate controls cost on fuel efficiency is about 2 to 4 mpg depending on how hard the climate control has to work which depends on how hot it is outside and how much work is required to cool down the cabin. If you use the cabin filter it will always cool air from the outside which over time is more energy intensive than using recirculating previousl cooled air from the cabin. Setting the climate control cooling temperature higher (e.g. 80) and at a lower fan speed also keeps the energy cost of the climate control system down.

Aerodynamic drags starts to eat away at the Prius c slightly earlier (than a Prius hatchback) despite the fact that a Prius c has a smaller frontal aerodynamic drag area because the Prius c notch back creates more rear end turbulence at higher speeds. So higher speeds hurt the Prius c fuel efficiency more than the Prius hatchback. However, because the Prius c is weights less and has less front aerodynamic surface - the Prius c has a higher potential for better fuel efficiency ( about 7% ) than the Prius hatchback at lower speeds (e.g. 20 mph) - with the AC on or off.

At very hot driving temperature, over 100 degrees Fahrenheit, I recommend that a Prius windows be rolled up and the air conditioner turned on to keep the cabin temperature below 86 degrees Fahrenheit Why? The Prius high voltage(HV) battery pack is air cooled and the Prius HV battery cooling system's air intake system gets its air from air port inside the cabin - hence, cool cabin air helps keep the HV battery cool and thus can help extend the lifespan of the Prius HV battery pack.

 

Great detailed write-up!!

 

Just to expand on this, a happy Prius HV battery is in a cabin where normal humans feel good generally in the mid-high 70's F. So if you have the windows down and are sweating buckets to save a couple pennies in fuel, it is not worth it. Run the AC, cool yourself off and cool down the battery. Also, you should run the AC periodically so that no mould or other nasty things grow in the vents. That does happen in un-used HVAC systems.

 

High Roller, your location is a factor, let responders know your region, to better picture your situation.

Where we are, we don't use the A/C much. Even quite hot days if it's short trips around town, just roll the windows down. For an extended highway drive, then yes, A/C.

 

When your A/C is on and running at fan speed 1 or 2 (how many bars are showing), you shouldn't notice any difference in mileage. I tested this a few times and couldn't see a difference as I cruised on the highway with my cruise control on.

You will, however, notice a big difference when the A/C is running hard, such as when cooling the car at the beginning of your trip. Here's what my gauge looks like when I run the A/C and let it cool my car down. I call it, the ladder effect =P

 

Whatever you do, just watch out for the back windows. My kids had them down at ~35mph. I thought the wind could yank trunk off the car. Front or all 4 windows down seem to be OK.

 

Just crack the rear passenger window and you can roll down one or both of the front windows and not get the buffeting.

 

I absolutely love my Prius C and I get 50 to 55 mpg in town which is mostly where I drive. My mileage goes to hell with the air on. It drops down to 30 to 35 mpg. Its a 2013 with only 2k miles. So basically my Prius C gets the same mpg as my Corolla in the summer. Any one else having that kind of terrible mileage.

 

Its not the A/C getting you poor MPG, its your driving style. I have my A/C on 24/7, and always get 50 to 55 MPG, if not higher.

 

How do you that?

With no A/C I easily get in the upper 60 MPG, but with A/C it's down to mid 40 MPG: Eco mode button use with A/C on.

 

Stay out of the power zone, easy on the gas and break early. Freeway drive around 55 to 60 MPH. Also I have only used Premium fuel, so this may help but not proven and often disputed on here..

 

It absolutely isn't my driving style. I drive exactly the same whether air is on of off. With air on mileage just sucks.

 

Have you tried in ECO mode? The A/C shouldn't affect the mileage that much.

 

i noticed the temperature setting on the air makes a BEEG difference. 74 or 72 degrees uses way less gas ( oops,,, battery) than 68 degrees. the fan speed itself is trivial. the A/C compressor runs off the HVAC battery pack while just the blower fan seems only to tun off the regular 12 volt. and it will "Auto" adjust anyway even though the Auto light is off once you redirect the vent to letz say vent and lower vent by pushing the direction button once.
~~and for me ECO mode is useless,,,, just another cute button to spill coffe on next to the EV button