By Mike Berry, Apex Technology
The E-Council Board is made up of a bunch of smart people. One of those smart people is Curt Kinder of Greener Air Solutions.
Kinder is a former Siemens engineer turned Jacksonville HVAC contractor, and he shared a great presentation he saw on SEER rating along with some of his own technical commentary and wittily named it “Don’t be a SEER-sucker.”
Before we get too far down this rabbit hole, we have to ask the obvious question. What the heck is a SEER rating?
SEER stands for seasonal energy efficiency ratio and is a metric for determining how much cooling (BTU hours) you get versus how much electrical energy (kW hours) it takes to run all the HVAC system components.
An air-conditioning unit’s efficiency varies when the temperature inside your house changes and when the temperature outside changes.
For example, the hotter it is outside and the lower you set your thermostat, the less efficiently your unit is running. The most important term in SEER is seasonal.
Indoor and outdoor temperatures vary greatly during the cooling season, and the masterminds behind SEER wanted to capture that varying efficiency with some sort of seasonal average.
Seems totally reasonable, but let’s take a closer look at the calculations and assumptions.
The document we go to is the “AHRI 210/240 Optional Short Cut Rating Method” (sounds like a method written by AC manufacturer lobbyists).
Here are the key assumptions:
• Outdoor temperature = 82 degrees (hmm, that doesn’t seem that hot)
• Indoor temperature = 80 degrees (is that what your thermostat is set to?)
• No humidity load (sounds like the writers of the document do not live in the Southeast)
All those assumptions result in a higher SEER rating. What if an AC manufacturer didn’t want to take a short cut and used the “AHRI 210/240 Bin Method Rating Procedure”?
This method is a weighted average of various outdoor temperatures. Outdoor temperatures of 90-100 degrees account for 7.8 percent of the rating, 80-90 degrees for 26.5 percent of the rating and 67-80 degrees for 65.7 percent of the rating.
Wait … what?
Sixty-six percent of SEER rating comes from outdoor temperatures below their crazy 80 degrees thermostat setting? Here’s a hint, when it’s 67 degrees outside, the SEER rating of open windows is infinity.
You may have just learned that SEER existed, and now maybe you wish you hadn’t. SEER is the main regulation metric for the Department of Energy, meaning SEER is here to stay. So, what do we do? Simple. Don’t buy SEER (also known as mathematical marketing by the air-conditioner manufacturers). Instead buy an efficient system (air handler, condenser, duct work, balanced air flow, etc.), and you want to buy it from an air-conditioning contractor who knows the difference. Hint: Curt Kinder is one of those contractors.
Mike Berry, EI, Mechanical Design & Building Science Lead with Apex Technology, is a member of NEFBA’s E-Council and regular contributor to Builder News. Contact him via email at [email protected].