I carry a small ceramic heater, this is the third one I have had, I used one on my boat, it worked fine, I bought a fancier one for the van that oscillated it died after the first year, I have another one steel bodied, about 6x8 inches, two settings 750W and 1500W thermostat controlled, branded Holmes, I have used it in the high 20,s F or around -3 Celsius it was fine van was toasty on low setting.