Over the last two days it has gotten cold here,for us ( lows in the low 20's Highs in the low 40's), and it is the first time I have used the Hurricane heating system. I have turned it on two mornings while it was still in the 20's and gone out to work in it a couple of hours later. By then it was in the 30's outside and maybe 60ish inside. As the day warmed up so did the inside temperatures to about the low to middle 70's. It seems that it will heat the inside to about 30 degrees warmer than the outside temperatures.
To be fair I did discover that one fan was broken, (crayon got past the drawer and broke/jammed the fan), and I did not do anything to add insulation around the windows,windshield, bathroom skylight, or fantastic fans. I also only let it run 6 to 8 hours each day and if I left it on longer it may have retained more heat.
I was just interested in what to expect from this system. I am not planning to go out in sub zero temps, but it would be nice to stay toasty in cold temps if ever needed.