a friend of mine gave me is old garage electric heater and it is in good shape and all , but its a bit big for my need... i would need about 5 or 6 kw but this one is 7,5 kw and wondering if its too big??? or as the old saying goes bigger is better ......is it worth the extra operating cost for less operating time??? please spare me the propane and ng is better lecture that was already ruled out long ago, it is free and work good.