I actually talked to Bob at Pro Products about this a long time ago. He gave me a few things to try. First, try bypassing the T-stat and just run the RHP straight off the wall and see if it goes higher. If so, then you have a t-stat issue. If that doesn't fix it, then try a different outlet. Bob mentioned something about some older houses/buildings have "funky" wiring that might not allow full voltage to reach the RHP thus basically throttling it. Also you can try putting something to soak up heat to amplify the heating like a flat piece of slate or flagstone or the hide. RHPs don't really warm the air per say. They warm objects under them which in turn gives off heat which does warm the air. If all else fails, you might need to step up to the next size of RHP.