Mike,
My unit is a Friedrich (correct spelling) Model YL24L35, 220 volt, 24000 BTU, with an EER of 10.0.
It is mounted in an opening in one end wall of the shop, centered in the width of the wall, with the bottom of the unit about 5 feet above the floor. The unit could have been window mounted.
After about three years of use, I think I could have used a 12,000 BTU unit............
There is no underground heat sink; summer temps here run in the high 90's to low 100's, with humidity to match. Winter lows MAY get into the low 20's or high teens, but usually bottom out in the low 30's and upper 20's.
I am in central Alabama. Monthly $$ average $25 or so.
Cheers,
Jim