Hello, I use a elec 1500w space heater under the seat of my '48 Cub. The tractor is in pole barn,covered with 2 heavy canvas tarps,with 4 inch thick slabs of sponge on top of fuel tank,and heavy carpet over them. In past, 20f or lower required space htr. I could put heater on timer. But that is only part of answer to lower elec bill. The mag heater would put the heat on the tractor,not warm the air. Might be safer,and more efficient than space heater, I dont know. My Dad used to leave His Cub outside all year,covered with tarps. If it wouldnt start with a little starting fluid,He put a small metal bucket filled partially with charcoal and lit it off,and put it under engine,staying right by it. I could do that,as I know it works,just trying to find something that works without me being right there,that I can use timer on. Some people who bought the Kats 300W Mag heater said plastic cover had meltdown. The temp on that unit stated 350-400F. The zerostart by phillips-temro has temp limit to 250F. I dont know if that would be sufficient to start tractor or not. Has anyone used the zerostart? Thank you for posting results!