MPG in Hybrid Mode

Does it run heat using the heat pump or using only engine heat, that is under the condition when AC is set to OFF and AUTO remains ON?

 

AUTO or manual is not what I was concerned. My assumption was that by "AC" Toyota meant the use of the electric heat pump or air conditioner similar to the "AC" on the fob for remote climate control. So, by turning AC OFF, I was thinking the car will not use the heat pump nor air conditioner, either AUTO or manual. But of course that means, if the heat is needed for the set temp and the car is running on EV mode, it will have to turn on the ICE. This should be easy to test. I will give a try on my way home today.

 

OK, that means "A/C" on the display has a different meaning from "A/C" on the fob. I just searched but I couldn't find clear distinction of those two usages anywhere in the manual.

 

OK, I tried AUTO ON, A/C OFF, set temp HI on my way home. Yes, as @Tideland Prius said, it did turn on the heat, but ICE did not come on. Thus it does use the heat pump even with A/C off. I also set the temp to LO. Cool air was blowing from the vent, but I think that was just ambient fresh air. Outside temp was 65F.

 

As I commented in the later on this thread, keeping A/C OFF does not turn off the heat pump. The heat pump will come on if the heat is needed for the set temperature. As @Tideland Prius explained, "A/C" on the screen means electric compressor for the air conditioner (cooling or dehumidifying) unlike the "A/C" on the fob which include the heat pump for heating purpose.

 

That would be my guess, but you also have to have the fan on at some level. If the fan is all the way down showing no bar, then entire climate control is off, I think. Of course, I would not know when the heat pump comes on. There is no indicator that turns on with the heat pump AFAIK. BTW, if you have done HV drive prior to switching to the EV mode, and the climate control needs heat, it does make use of engine heat despite the fact you are now on EV mode. I can feel the difference in temperature of air coming out of the vent with ICE previously on prior to EV mode vs no ICE.

 

I think I have felt warm air coming out of the vent when I had a fan off. This often happens in my car when I am driving on a cold morning with HV for a while with heat on, then turn the entire climate control off (thus fan is off) and switch to EV. Even without forced air circulation, the direction of flow is such that warm heated air from ICE comes through the HVAC system, so it seems.

And yes you are correct PRIME is the only model with a heat pump.

 

Was outside temp colder than cabin temp? I wonder in the absence of ICE firing up if there is no other heat source to be diverted to HVAC system.

 

Think perconditioning! I don't know how it works either, but I has noticed that I can't get perconditioning to work from the fob under various conditions with our plus.
I found two links that help explain how it works, not that I get even most of it yet.
Inner secrets of the Toyota-Denso heat pump revealed
How does the heat pump work in a Toyota Prius Prime plug-in hybrid?

 

That, I don't know the answer. As I commented, there is no indicator that comes on when the heat pump is on. Knowing how the PRIME is designed, I would think whatever the most efficient way to deliver the desired heat is used. That means, as long as ICE is on and there is available wasted heat to be used, the heat pump should stay off. But I am only guessing here.