If his door is open as he said, it does not seal 100%, and as he said
its running continuosly, being an old unit pulling 400-500 watts it
could easily cost him 50$ a month since it is not operating correctly. A
new 19.5 cu ft Sears, the most efficient made 3 years ago costs me apx
3.5-4$ a month verified by me with a Kill-A-Watt. Average efficiency
increases on new units over 15+ yr old units is 66%, often you save much
more from old units not running at their peak, as in leaking doors or
not being cleaned