Heat Pump Defrost Energy Penalty Calculator
Quantify how much energy defrost cycles add to your heat pump's daily consumption and compare it with the building load.
Engineering energy estimate—validate with measured load profiles before committing to design changes or performance guarantees.
Examples
- 6 cycles, 9 minutes, 4.8 kW compressor, 6 kW auxiliary, 68 kWh load ⇒ 10.44 kWh/day defrost energy penalty. That represents 15.35% of the daily heating load.
- 4 cycles, 7 minutes, 3.5 kW compressor, optional fields blank ⇒ 1.63 kWh/day defrost energy penalty.
FAQ
How should I estimate compressor power during defrost?
Use field measurements from a power analyzer or manufacturer data for the reverse-cycle operating point closest to ambient conditions during defrost initiation.
Does the calculator account for heat recovered during reverse flow?
No. The penalty assumes energy consumed during defrost does not provide useful indoor heating. If your system recovers some heat, reduce the compressor input accordingly before entering it.
Can I model variable defrost durations across the day?
Average the duration weighted by how often each event length occurs. For more precision, run the calculator separately for each duration category and sum the resulting penalties.
What if auxiliary heat is staged rather than fully engaged?
Multiply the rated power by the duty cycle active during defrost (for example, 6 kW strips at 50% duty become 3 kW) before entering the auxiliary input.
Additional Information
- Result unit: kilowatt-hours per day consumed by defrost events.
- Auxiliary heat input defaults to zero when the field is left blank.
- Daily heating load is optional and only used to calculate the penalty share of space-heating demand.