HVAC Auto Setting

what happens if you turn up the temp?

 

what happens if you press the a/c button after hitting auto?

 

The A/C light is on but that doesn't mean the compressor is running. the only time it will run is if there's a call for defrost or its too warm inside. In short - it makes no difference whatsoever.

That said, if you hit the A/C button and turn it off, the system remembers that till you hit auto again.
Also note that setting the temp to 78 will burn quite a bit more gas to keep the coolant warm enough. Set it lower if you want to save some gas. You're burning FAR more energy keeping it hot than you ever will leaving the A/C engaged.

 

The AC still cools the air even with the heat on, it just passes the dry, cooled (and conditioned) air through the heater after the condenser.
This of course means the cabin will take longer to warm up as you are now blowing cold air through the heater as opposed to ambient.
AC on still has the advantage of drying the air, keeping condensation down.
I don't know for sure about the Prius, but with most cars, if ambient is 4 deg C or less then the AC doesn't operate anyhow, to prevent the condenser icing up.

 

I think that partly explains why my winter mpg is worse since moving to Vancouver 2 years ago from Edmonton. I leave my climate control on auto all the time. I just set the temperature and let it do its thing. In Edmonton during the winter even on those -30 days I never did worse than 42 mpg.
In vancouver where it rarely ever drops below freezing but rains a lot in the winter I average around 36mpg. I'm thinking the ac is working harder in Vancouver year round to keep the humidity under control, compared to the dry climate in Edmonton.

 

The A/C isn't costing you a penny in MPG. The compressor barely runs at all in that situation, and only at its lowest speed for a minute or so at a time. All it has to do is lower the temp of the coils just enough to create condensation. Even in 100' heat, running full blast, the A/C *might* cost you around 2MPG.

People need to get old ways of thinking out of their heads. This is not the A/C system of years past. Its a multi-speed electric compressor that's designed and computer controlled to very tight specs with the purpose of minimizing current drain. Use of the ECO system mode even further reduces the drain. But at its lowest speed, that compressor can run a VERY long time without draining the traction battery. The impact on MPG is negligible, if its measurable at all.

 

This is on a 2010 Prius hatchback, so not sure how relevant, but anyway:

If AC button is not pushed (light on button off) and I push Auto button, AC continues to be off. The ONLY* time I've observed AC come on, when not requested, is if I set mode to Heat/Defog. Then it will run AC intermittently, under some conditions. It doesn't light the light on the AC button, but my ScanGauge shows AC wattage dancing between various values, zero to maybe 200. If ambient temp is low, near freezing, AC still stays off, even in Heat/Defog mode. If ambient temperatures are higher, AC may come on. I'm not sure what the parameters are, might be it's sensing humidity, but I'm really not sure.

* Barring pushing Front Defog button, which always switches on AC, and lights the light on the AC button as well.

 

I agree tideland, the hills in my commute among other factors(traffic) likely are the main cause of my mpg drop.
I didn't know that about the AC rdgrimes, although i kinda figured the AC system in the Prius was especially efficient just as the rest of the car is designed to be.
I guess i was going off the way AC was used in the old family cars growing up. My parents would use it very sparingly just to take the edge off the heat, and they would rather open the windows or sweat it out than run AC figuring it wasted lots of gas. They still do it today in their 3 year old non hybrid car, which i'm sure is more efficient than cars 10-15 years ago. I guess old habits die hard as they say.

I've even had people riding in my car during the summer a couple of times see the AC light illuminated and turn it off for me(they felt it was too cold and thought i had absentmindedly left the ac on full blast). Then I tried to explain to them i would just turn up the temperature on the climate control system and the ac would only run as needed as it was automatically controlled.
I think its a misunderstanding/mistrust some people still have of automatic climate control systems in general. Just set the temperature and leave it alone!

 

That's a scary picture.

 

Judging by that Picture I'm 99% certain you live somewhere between Edmonton and Winnipeg.

 

Must be an Ice road trucker on his way to work

 

Digital displays just don't impart the proper impact. A needle gauge would be better, kinda bending at the lower stop, in the icy blue zone.