Surprise, its summer and our AC broke down.

We were quoted prices for installation of the current standard (SEER 14) AC units (about $6500 unit cost and installation) vs Trane's SEER 18 AC units ($10,100 unit cost/install). The sales rep for the local HVAC company said the SEER 18 AC units was significantly more efficient than even the SEER rating indicated. The reason, he said, was that the unit has a variable rate compressor. He said normal online SEER savings calculators. Like this one underestimated the impact of the variable rate compressor.

This is for our upstairs in our dual zone system. We live in a rather humid area in the summer, and the unit is used for both head pump and AC. We plan to live in this home for a long time.

Is it worth the $3500 bump in price to get a unit with a variable-speed compressor? Are the online calculators underestimating the bump up to a variable speed compressor? In general, when is it worth the price difference to get a variable speed compressor? Help me (and everyone else who sees this question) be better informed when talking to their HVAC sales rep!

  • The cost aspects of this question should probably be removed, and the question more focused on performance increases of the variable compressor. Cost is a bit too subjective, and varies wildly from place to place (and over time).
    – Tester101
    May 29, 2015 at 14:25
  • Doug, I am exactly the same situation as you were at the time of your original post. Which option did you choose? How do you like it?
    – Bronwen
    Jun 20, 2017 at 19:29

2 Answers 2


The test procedure for determining the SEER is quite elaborate, and involves measuring the efficiency at a variety of simulated outdoor temperatures. I'm not sure what the basis for the sales rep's statement was, but without more information (i.e. specific numbers) I wouldn't put too much stock in it. The SEER is not just calculated at a single fixed situation.

As for whether it makes sense, that depends on your climate, the size of the area being cooled, the local price of electricity, etc. I would just use one of those calculators like you've linked to to determine the value, but make sure you get accurate numbers for all the inputs. The cost of electricity varies widely throughout the US, so get a current number for your area in the summer and then maybe round up a bit to account for the gradual rise in prices.


You may also want to check with your electric provider, there may be incentives for buying a more efficient system. I just installed a Trane 20 SEER system and received a $900 rebate from my electric company.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.