thanks for the help gentelmen, I'm still undecieded on this. we have friends who use these type of heaters to heat there whole house, but they use propane, which is very high. Said friends save 250 per month. another friend just bought two of them, and the jury is still out on if its helping them or not. my wife and i heat with natural gas, and figuring out our cost per day, between gas and electric, i just wonder if it would help or not. Our current figures say, if we could use the gas as a back up and use the other heater as the main source of heat we would save 1.00 per day. not much if the manufactures numbers are true. At 397.00 and 450 for either unit, thats alot of money. Both manufactures say their unit will heat the whole house, just seems unreal to me.