I have a 12 year old 3.5 ton 12 seer Carrier electric heat pump. I'm told that parts are rusting (coils?), it has a small refrigerant leak and basically it's got about 1-2 years left. I have a quote for a 3.5 ton 14 seer Carrier Performance series ($8,000, installed) and I'm being told that the new Carrier will be much more efficient and cost less to run (50% less.) Does 2 seers really make that much difference? Is the Infinity a better product?

Forgot to add, I live in the southwest and it routinely gets over 100 degrees in the summer. Dry heat & all that - but 100 degrees is still HOT.

50% seems like a steep claim. I moved from a 10 seer to a 13 seer and did not see at big savings. This was also on a 1300 sq ft house and i live in Oklahoma. We can get hot weather, but not as much as you. It's really a complex question as to how much the unit runs, size of house, etc. 13 seer is the standard here these days for new units. you should ask for the price on the base unit for comparison.

It may very well be more efficant but no way will it cut your cost by 50%. More like 8-15 %

50% is not at all likely!

Ideally you can get a 10% savings per SEER jump, but realistically its probably less. I'm guessing somewhere in the 10-20% range but depends on your ductwork and other factors.

It is always best to get multiple quotes from multiple vendors on various SEER ratings.