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How much more a dirty unit uses

Updated · reviewed by certified technician

In short US Department of Energy data: a dirty filter raises consumption by 5–15%. Lawrence Berkeley Laboratory measured that coil pressure drop doubles in about 7 years of use without cleaning, with 5–7% less air and up to 10% more fan energy. A clogged outdoor coil adds more, because the compressor works at higher pressure.
Explanatory diagramEstimated energy: power × time
Estimated energy: power × time
  1. Average electrical input, in kW.
  2. Operating time, in hours.
  3. Estimated energy, in kWh; actual use varies.

BTU describes thermal capacity, not electrical consumption directly.

Coil fins full of dust and fluff, before cleaning
Coil fins full of dust and fluff, before cleaning

What is really happening

US Department of Energy data: a dirty filter raises consumption by 5–15%. Lawrence Berkeley Laboratory measured that coil pressure drop doubles in about 7 years of use without cleaning, with 5–7% less air and up to 10% more fan energy. A clogged outdoor coil adds more, because the compressor works at higher pressure.

The calculator below shows the estimate for your unit. See current rates on the Prices page.

The evidence

Calculator: how much more a dirty unit uses

This is a scenario, not a measurement of savings. BTU is cooling capacity, not electrical consumption. Use measured average input where possible. The chosen percentage is an assumption and cannot be inferred from dirt alone.

What to do

Mechanical pressure cleaning of the evaporator, blower and pan inside a collection cover, then sanitising; filters washed every two weeks; room humidity kept between 40 and 60%; the unit dried on fan mode before winter. No sprays over dirt, no bleach in the unit, no refrigerant "top-ups".

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The information on this page is educational and based on cited sources; it does not replace medical advice. We do not do repairs, installation or refrigerant circuit work.