Skip to content
Sign in

Refrigerant charge

Refrigerant charge is the amount of refrigerant in a heat pump system, which must match the manufacturer's specification for the installed line set.

Editorial staffEdited by heatpumpwiki

History 1

Refrigerant charge is the amount of refrigerant in the system. Too little or too much reduces performance. NIST's modeling found a 30% undercharge could raise annual energy use "by as much as (17 ~ 23) %," and a 30% overcharge by "(10 ~ 16) %."Source 1 ENERGY STAR says an incorrect refrigerant level can lower efficiency by 5 to 20 percent.Source 2

The installer sets the charge using the manufacturer's procedure, which includes added refrigerant for longer line sets. Checking or adjusting charge must be done by an EPA Section 608 certified technician.Source 3

Sources

  1. 1.Sensitivity Analysis of Installation Faults on Heat Pump Performance (NIST Technical Note 1848). National Institute of Standards and Technology. Accessed Oct 25, 2026
  2. 2.A Guide to Energy-Efficient Heating and Cooling. ENERGY STAR (U.S. EPA). Accessed Oct 25, 2026
  3. 3.Section 608 Technician Certification Requirements. U.S. Environmental Protection Agency. Accessed Oct 25, 2026

More in Glossary

  • AHRI certificateAn AHRI certificate shows the certified efficiency ratings for one exact combination of outdoor and indoor heat pump equipment.
  • Aux heat (auxiliary heat)Aux heat is a backup heat source that a heat pump thermostat turns on automatically when the heat pump needs help.
  • Btu (British thermal unit)A Btu is the heat needed to raise one pound of water by one degree Fahrenheit, and heat pump capacity is given in Btu per hour.
  • COP (coefficient of performance)COP is the heat a heat pump delivers divided by the electricity it uses, at one set of conditions.
  • DefrostDefrost is the cycle in which a heat pump briefly reverses to melt frost off its outdoor coil.
  • EER2EER2 is a cooling efficiency rating at a single hot test condition, in Btu per hour of cooling per watt.