[bradgranath]

It's not just certification/permitting. The manufacturers often state that the unit must be verified to be installed by a qualified technian or the warranty is void.

Around here anyway, I was getting quotes of 20k for the install & equipment of a central air handler and the outdoor unit.

I'd be dead before the thing paid for itself in electricity cost savings. $20,000 ÷ (~90yrslife - 40yrsold) = $400 / year of neccesary savings to break-even as my casket is lowered into the ground.

[JeremyPOsborne]

Most don't have a payback if the cost of electricity is too high. Let's make them lower cost up front and lower running costs so it's a no brainer when replacement is due.