At this size level, the difference between 13 and 14 SEER is about 100 watts of power consumption. That's not a "throw away" issue, but it's close. If you run your system 1,000 hours a year, that's 100 kilowatt-hours of annual savings (about $10 a year of power savings at average rates) for the 14 SEER over the 13 SEER.

So, I think you need to factor in some other issues in making that decision, as the choice of 13 or 14 SEER is not in itself significant enough to make your decision.

Everything has to match the 14-SEER. I like the 14-SEER if it has the Copeland Scroll compressor & a TXV on the Evaporator.

The evaporator will do better in milder weather if it has a TXV metering device.

Add an adjustable differential room thermostat & the SEER can go up. Longer run-cycles are far more efficient than short run-cycles!

Do some research & make your own decision.

The quality of the installation, ductwork system & PROPER airflow are the FIRST essential, & are (IMO) more important than ultra high SEER equipment.
- udarrell

Here is a link that might be useful: http://www.udarrell.com/airconditioning-sizing.html

Yea, probably not much diff in operating costs. Some utilities might have a rebate for 14.

Be sure you are getting it though. Some 14 SEER units can't get 14 without that brand's matching variable speed blower inside. Some can't even with a variable speed blower!