IT IS 34 DEGREES WITH A WIND CHILL OF 28. I PUT IT IN MY UNUSED BACK BEEDROOM, THE COLDEST ROOM IN MY APARTMENT. THE ROOM SIZE IS 12 X 8 WITH 7' CEILING . AT THE TIME IT WAS 62 DEGREES IN BEEDROOM AND IN 45 MINUTES IT BROUGHT IT UP TO 65, JUST THE TEMP I WANT TO KEEP THAT ROOM AT. AND I HAD IT SET ON LOW (325 WATTS). AND IT IS THE ONLY HEAT SOURCE IN THE ROOM. GREAT LITTLE HEATER AND ONLY USING 325 WATTS.