Cabin Heating?

Yes, and this has been pretty thoroughly documented and discussed at least as far as the 2017-2022 models go.

 

idk for sure, but can only assume the engine will come on automatically unless you can figure at what temp the heat pump is no longer effective and turn the heat off before that.
on the plus side, i've read the heat pumps are very effective down to about 14f.
a bigger problem has been clearing the windscreen

 

I had a Nissan Leaf with a heat pump. At about 0 °F it would transition to resistive heating (Leafs don't have an engine to heat things).

With the Avalon I'm putting on a 1,500W circulating block heater. I've used these before and they're wonderful. They'll heat the engine up to 180 °F, so I'll be getting heat from the get go without idling. The same would be true of a PHEV, although I see the drawback of having to plug in two different parts of the car overnight with one turning on towards the morning.

 

I still don't understand how they didn't design in a relay & output terminals such that power from the charger input could be diverted to a block heater after charging was completed. Seems like a big miss.

 

OEM block heaters that they put on at dealerships are wimpy and are meant to be left plugged in all night. I don't think any manufacturer ever thinks about how a nice toasty engine that's been on a 1,500W (or better in Europe) outlet for a couple hours would be really nice for those of us that live in the bitter cold. But then again, most people just idle their cars via remote start to get a nice toasty ride in the dead of winter.

The Leaf had a function that allowed the cabin to be preconditioned (winter or summer), even off of a standard 120V outlet that was pretty slick. I was upset when the phone app stopped working when AT&T shut down their 2G network, but it still could be programmed into the dash.

Personally I think new cars are cool in a lot of ways, but they don't seem to offer many things that are practical to me. In fact, I'd say that modern vehicles are less practical than older cars in many ways.