[tom66]

The bigger drain for you will be using the heater over the speed of the car.

This is misleading and/or wrong! The heater draws around 2kW once the car is at temperature (assuming e.g. 3-4C outside and 20C inside the car). Whereas plowing along at 70 mph uses between 16-25kW. Speed has a significant impact on the range of any EV.

One of the reasons EV range is worse in the cold is a combination of battery performance being worse (the GTE is no exception, and it does not heat the battery pack like some other EVs) and the cabin heater. But the effect of the cabin heater is much less significant at speed. It's much more of an issue for a driver that does a city commute consisting of a lot of stop and go driving, with time waiting at lights - in an ICE car that heat is 'free' from even a stopped, warm engine, but an EV has to use the battery to provide that at all times.