I have two shops in Maryland, one has AC the other does not. When the temperatures soar, the production in the unairconditioned shop definitely suffers. (Even the younger techs struggle when sweat is pouring off their heads and their uniforms are soaked). We have multiple swamp coolers which are okay if the temps are 85 and below with reasonable humidity, but the old norms of our summer climate seem to be fading and its getting hotter each year. I plan to install central air in the the other shop this year. It will add to the overhead, however the increase in productivity and morale will outweigh the utility bill.