My experience showed me although yes, the instant consumption Is speed related, it’s not only it. It’s also the road elevation, the wind speed, the road surface, the temperature outside. And yes, I agree that 20 kW is high for 60 mph, but it was only used as an exemple.
My experience in tough winters taught me that for a given trip of a given length, if I keep the instant consumption under a certain level, I’ll make it without needing to charge before I arrive to the destination. And I love the way the GOM on the Bolt EV works : giving the estimated range based on the last trip. This is awesome, because if I know I went 75 mph last trip and the next trip I will rarely go over 65 mph, I can very well "guess" what the real range should be for the next trip, because the GOM gives not only the range, but a minimum and a maximum ! Awesome stuff that none of the competitors have. In my Volt, it was a mess, because the GOM was based on the history of the runs and it was never easy to predict the moment when you should use the battery so that you arrive home with 0% SOC (on long trips and when you want to use the battery in city and not on the highway, if you get home with battery available, it means that you used too much gas). I use a lot MyChevrolet app, which for whatever reasons works flawlessly for me. Seeing the % of battery in real time helps a lot to learn how your Bolt EV works and, more important, to know what are its capabilities.