Warwick, R.I. I've been using a 1500 watt heater and it's worked well so far (it's been down to 25F) but it's going down to 14F tonight and I already found a few more drafts...
I'm getting a 6000 BTU propane heater which can be a wall or floor mount, indoor rated, vent free w/ auto CO shutoff this week. I will also bring in a 1/2" fresh air vent
line from outside w/ a diffuser at the end so it wont get drafty (like you do w/ a wood
stove), to help feed it and keep the CO negligible.
I had one of those heaters before, but a 30K BTU in my basement and did the same thing w/ an outside air
line suppling it and never had a CO problem even w/ an air tight house.