TA, I don't know about butane, HDR and others would know that. As a minimalist, I just use the Coleman single burner stove with the green canisters. Last about a week in general. For good or for bad, the canisters live under the bed, lol. I figure the little green bottles are as safe as you can ever be with combustibles, no long lines running around the van from an outside 20 gallon bottle.
When it comes to heating, I've only ever used the stove for a bit in the morning just to take the chill off. Don't know about Happy Camp, but where I live it's supposed to get down to 10F this week and snow.
EDIT: silly me, I never thought to warm some water while heating up the van in order to take a sponge bath afterwards, duh ...