Not electric blanket.... electric mattress pad.
I have a Ford Transit van which I have converted to a "stealth camper". It's not for recreational traveling per se, but more to keep me out of hotels when on road trips for other reasons. (I stay in hotels at work, I am NOT going in one on my own nickel). I have basics.... small fridge, induction cook plate, porta potty, sink with 5G of cold water. No shower, no water heater, no furnace. (No propane)
The mattress pad I have is about 80W. It has a thermostat which cycles on/off. (Wattage is constant when on) I turn it on medium while driving which gets the bed nice and toasty. When I go to bed I turn it to low, and that, with a good sleeping bag, keeps me more than comfortable.
I have a 300Ah house bank and a 3000W pure sine inverter. On a cold (30's) night the pad pulls about 50Ah over an 8 hour period. Plenty of juice.