An engineering study found three main areas of concern:

Duct Leakage

  • Average loss per home = 360 cfm
  • Average loss (as % of sq. footage) = 19.5%

Refrigerant Charge

  • 62 % were overcharged
  • 23 % were undercharged

Sizing of the Unit

  • 88 % were oversized
  • 2 % were undersized

North Carolina Alternative Energy Corp.

This non-profit organization examined air conditioning manufacturers’ efficiencies versus the actual efficiencies that resulted after installation

  • 90% of the units tested exhibited some sort of energy-wasting problem
  • 50% had an improper refrigerant charge
  • 40% failed to meet minimum air flow criterion. 20% were barely inside the range specified by manufacturers.

Did You Know?

  • A deficiency of 20% in air flow reduces the SEER rating by 17%.
  • A 15% return air leak from a 120° attic could reduce a 12 SEER to 6!

Texas A&M University

  • Found a 23% refrigerant undercharge could result in a 52% efficiency loss

Pacific Gas & Electric

Found the average heating energy savings for:
1. Repair of disconnected ducts was 15%
2. Repair of diffuser leakage 7.5%
3. Correcting low air flow 5.6%
4. Repairing leaks and correcting refrigerant charge 18.4%


  • Found that heat pumps lost almost 50% of their efficiency after 20 years, even if a typical “dust stop” filter was installed. In 20 years, a 12 SEER unit could degrade to a 6 SEER. This would double the energy cost!
  • Louisiana State University and Gulf States Utility
  • Found consumers could save about $30 per month just by making sure that their air conditioning system was cleaned and serviced regularly.

HVAC Manufacturer’s

  • Data shows a condensing unit with an SEER of 13 matched with an old air handler would decrease the SEER to 9.2, resulting in 30% less efficiency.