I am having a house build and have the choice between a 10 SEER air conditioner for $3700 and a 12 SEER air conditioner for $4500. Which one should I get and what is a SEER? The house will be in Irvine, CA which means that the general climate is sunny and mild (i.e. perfect golfing weather) except for a few weeks in August when the temperatures may creep up into the 90's. A third option is to do away with the air conditioning altogether and implement some other strategy for cooling the house (I am open to suggestions).

As a side note, I would add that Irvine is also a short distance from Disneyland and less than an hour's drive from Legoland, which is an excellent place to enhance the education of the next generation of Green Engineers.

-- Tau-Mu Yi (tmy@uci.edu), September 21, 2004

Answers

SEER stands for "Seasonal Energy Efficiency Ratio". It's the ratio of total seasonal cooling output in BTUs to total seasonal energy input in watt-hours. (seasonal means its averaged to include part load conditions - it's not just a measure of performance at peak load)

So a SEER 10 AC unit removes 10 btus per watt-hour of energy input.

Payback will vary depending on electricity rates, unit size and cooling demand. As a very rough estimate, going from SEER 10 to SEER 12 might save you $200/year - a 4 year payback on your $800 investment. Keep in mind that a 4 year payback is equivalent to a 25% return on investment - lets see you do that in the stock market.

So go for the better unit. But don't forget that better insulation and windows will save you money too!

-- Chris Schaffner (chris@greenengineer.com), October 01, 2004.