For a two bedroom in 30-40 degree weather the smaller 10000 BTU should be okay, if its colder you might need the bigger 30000 BTU standup (tall) heater. These are the ones that have wicks and use k-1 white kero. I heated with them for years...clean the wicks every so often and let them burn off once in a while too. Change them every year if you use them a lot.