I have about 1500sf in my garage shop. I have a 2ton heat pump/ac unit forced air.. But I have LPG gas back up for it. I always turn down the thermostat to 55deg when I close shop. When I come in, I turn it up to 68. The gas backup system fires up and brings temp to 68. Then the heat pump keeps it there. Gas will only fire if the thermostat is changed by more than 2 deg or if the outside temps are below 32deg. Works Great for Me..:thumbsup::thumbsup: