Put it in my rv and it went down to 16 degrees overnight at the racetrack this thing ran perfect all night it seemed to be able to do the job till around 4 am then it fought to stay in the 50s in there but it kept me from freezing and after I started the engine to bring the temperature up again it was fine needed 2 for my camper but if it was 25 and above it would be fine and it's actually a shuttle bus convertion 24 ft so it wasn't going to overpower mother nature that night but it was cozy in the 30s and above with just this little 1500w heater . Note run it ahead of time to burn the new off it smells like a meth lab till it's had a couple hours to cure out the elements