The EPUs don't work so well for high heat, although they do well in cold since when cold you'll just be using the bunk heater. IMO, EPUs are junk...not if, but when those batteries get drained you're truck will be idling for hours, causing emissions issues in those junk Freightliners. Another con to those junk EPUs...when they do start giving problems you'll darn near have to empty out the sleeper to get it worked on as they're installed in the bottom of one of your cabinets....just genius.