At what speeds, and over how long a distance, did you get 230 Wh/km?
Because I live up in Port Perry I am typically on country roads with 80kph speed limits, so I drive 80-95, very efficient speeds. If I'm heading into Toronto I have been sticking to 100 on the 401 just to see how efficient I can be (normally I'd drive 110)
I keep the cabin at 18.5C, not hot. I find that very comfortable.
I will experiment as the temperature warms up to see how this changes. If we get a 4-5 degree day and I need to travel into Toronto I'll measure it again.
As for a full charge in Niagara to reach Cranberry PA, yes, I agree (with mrElbe), and that's why I'm thinking of departing in the morning, it's about 2.5 hours to Niagara, then I can do something fun with the kids while I charge up and have lunch too. Or even better I stop in Buffalo and charge there. No bridge crossing risk after that. Should be easy to get to Cranberry after that.
That's the thinking so far ... less than 24 hours after I posted my initial question. I am evolving things as I research. I really appreciate everyone's feedback and I hope this is useful to others too. Many of us must be thinking of this kind of trip at some point, and who knows when Buffalo gets built.