I'm changing my heat pump system. I got a quote for a Carrier 13 seers unit. My house is 2200 sq. ft. ranch house with 9' ceilings. Do I need to upgrade to a 15 seers unit. I have no shade on the house. I just want to make the right choice.

Would take at least 50 years to revamp the cost difference, you would not notice the difference in power bill with a 15 seer unit

Basically, seer ratings mean how efficiently the system uses its electricity. Higher seer means more energy efficient. The seer is calculated over the entire year, so the difference between 13 and 15 seer is very small and your monthly bill will hardly change at all. You should be more concerned about getting the right size unit for the size of your house (probly 4.5 tons cooling capacity) than the seer rating. Just because the seer is higher, doesn't mean it will provide more cooling. Over time, you may save money on your power bill by going with the 15 seer, but it will take a while. Its at your discretion if you want to spend a little extra now to save a little extra later or not

I bought a 16 SEER unit replacing my old 12 SEER and the reduction in both electric and gas bills has been more than noticeable. Calculations are something like you save 29 cents per day per SEER. But you save that 365 days per year or over $1000 per increase in SEER efficiency per 10 years. So the real difference over a 10 year (short) life of the unit between 13 and 15 SEER is around $2000. Pretty much the difference in initial cost, but remember that Duke Power has asked for a 15% rate hike... that's where it will get you. Then all of the sudden you are playing with the thermostat to keep bills under control and are never comfortable again.