Have you considered that more insulation would cost _nothing_ to run,
and enough of it could even get you down to running one A/C unit?

--
Cats, coffee, chocolate...vices to live by

Ya, but I'm not sure what kind of insulation would hold up to a full time
machine shop. The insulation that is there, is a 4' wide roll with a green
sort of plastic facing the inside of the shop. The plastic is starting to
get holes and stuff in it from the years of abuse.

I've seen shops where they have sprayed insulation on the inside of the
walls. After a year or two, the walls are black with carbon dust and chips
that can't be effectively cleaned.

I'm just looking for a quick and easy solution, cause in the next few years
I'll probably be building a larger shop at a different location. Or, selling
the whole business and starting a different one.

Anybody looking for a small owner financed machine shop with a reasonable
customer base?