Understanding Energy Impacts of Oversized Air Conditioners

Research output: NRELFact Sheet


This NREL highlight describes a simulation-based study that analyzes the energy impacts of oversized residential air conditioners. Researchers found that, if parasitic power losses are minimal, there is very little increase in energy use for oversizing an air conditioner. The research demonstrates that new residential air conditioners can be sized primarily based on comfort considerations, because capacity typically has minimal impact on energy efficiency. The results of this research can be useful for contractors and homeowners when choosing a new air conditioner or heat pump during retrofits of existing homes. If the selected unit has a crankcase heater, performing proper load calculations to be sure the new unit is not oversized will help avoid excessive energy use.
Original languageAmerican English
StatePublished - 2015

NREL Publication Number

  • NREL/FS-5500-64189


  • AC
  • air conditioners
  • controls
  • crankcase heater
  • oversized air conditioners
  • parasitic power loss
  • residential air conditioners


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