I've used a 45,000 BTU Reznor in my garage/shop for over 20 years. I leave the pilot light on year round with the thermostat set down to 55. In the winter if I want to work in the shop, I can raise the temperature to 70* in just a few minutes. The room is 24x28x12. There are no windows, two walk-in doors, 2 10x9 garage doors. The walls have 2x6 studs and are sheet rocked over fiberglass batt insulation. The ceiling is blown with 12" of fiberglass insulation. It is not perfectly air tight around the garage doors, but heat loss is not too bad. I can not compare this heater with any other, but it has worked well for me.