Well it is 105*F in Austin right now. But, thinking into the future 7 months from now: would it be more efficient to use the seat heater, and dial back on the heating via the HVAC system so the ICE does not need to fire as often?
Its probably not since the heater may use more power than the fan motor. My seat warmers are butt burners. I dont use the seat heater. I would trade it in a second for an air conditioned seat like my wifes Avalon. Which is hot or cold depending on the setting.
During warmup, probably. Once warmed up, the heat is free as long as the engine doesn't cool down too much.
The electric seat does not cause the ICE to spin up when stopped. Running the CC will. Once the ICE is at operating temp it really doesn't make a difference. If it is cold enough for the ICE to run to keep itself & you warm then I'd turn off (or down) the CC & use the seat. I've had way too much experience these last few winters in this department.
I think the point of seat heaters (which I've had in cars since 1978, with the exception of my 2005 Prius) is to keep you warm until the cabin warms up sufficiently for you to be comfortable. A warm driver is more relaxed and less likely to make mistakes. Once the cabin is warmed up, they aren't needed. In my two Saabs, the seat heaters were on timers and turned on and off automatically.
I doubt that the power used by seat heaters is even measurable as reduced FE in real world driving. While it is a challenge to remember the chill of a cold November in late June, the comfort of heated seats on those cold winter days is priceless.
Coming from someone who experiences real winter (temperatures quite a bit lower than freezing) routinely, the suggestion is take advantage of the seat heaters and keep the engine (coolant-supplied) heater set to low. Remember, the blower must always be running to keep the windows clear anyway.
