Shop Heat

I have a 40x60 shop with 11' interior walls.this morning in okla. it was 15 degrees.but it was 42 in the shop.I have 2 window style heat and air units.one in each end of shop.best I could find at low's that run on 110 v.just cut holes in the shop and installed throw wall.turned them on this morning and its probley about 60 degrees now,(4 hours later)the main thing is good insalation.It doesn't get that cold here as a rule,but a few years back we got 28 days in a row that it never got above freezing and I never turned on the heat,didn,t have any projects going,but the shop never got below 40 degres.heat from the earth coming up through the concrete floor I guess.anyway the units weren't real cheap but they work pretty well and were fairly easy to install,no duct work involved.they probably cost about $12.00-15.00 a day to run both of them.of corse I don't have to run very often.:popcorn: