<snip> I'd like to calculate a trip to our favourite ski hill with the Monkey Bars & a roof box, however it's summer time so I don't know what my Wh/km in winter would be with the roof box. <snip>
Or do I have to wait until winter and mount the roof box and go for a test ride in winter conditions to find out the actual Wh/km and enter that in Reference Consumption? A little more instruction on using the Reference Consumption combined with Outside Temps, Road Conditions, Wind Speed, etc. would be appreciated.
Great question, @bpjod and I would tend to agree with @WannabeOwner that it should be roughly the same % decrease as Summer. Maybe a bit more as you'll be using the Heater instead of the Air Conditioner.
I think it would be quite comical if you took your Bikes or a Kayak to the ski slope in the dead of Winter. Likewise, take up your skis to the slope in Summer. I imagine people would give you some interesting looks.