Industrial Heat Pumps & Electrified Thermal Systems calculator
Air-Source Heat Pump Defrost Energy Cost Calculator
Use this calculator when an energy manager, service lead, or controls engineer needs to put a cost on defrost behavior in an air-source heat pump system. It is most useful during winter operating reviews, control strategy tuning, and project screening when frequent defrost can erode expected savings and increase maintenance work.
What this calculator does
- Estimate seasonal defrost operating cost for an air-source industrial heat pump from defrost kWh, electric tariff, scope share, and fixed service cost.
- Use it when energy or maintenance teams are reviewing cold-climate air-source heat pumps, outdoor process hot water skids, or frost-prone heat recovery equipment.
- The result estimates the operating cost associated with defrost energy use and related seasonal service.
Formula used
- Variable defrost energy cost = defrost electricity use × electricity cost × defrost operating scope
- Total defrost energy cost = variable defrost energy cost + fixed defrost service cost
Inputs explained
- Defrost electricity use: Use trended or estimated kWh for defrost heaters, reverse-cycle operation, fans, pumps, and controls over the review period. BAS trend data for defrost hours and heater status is usually more reliable than a rough nameplate estimate.
- Electricity cost: Use the blended site energy rate for the same period, or a modeled marginal rate if you are evaluating savings. If demand charges are materially affected by defrost timing, include them in the effective rate or review them separately.
- Defrost operating scope: Use 100% for the full winter season or full equipment group. Use a lower percentage for one unit, one shift, one climate period, or only the subset of hours when frost conditions are present.
- Fixed defrost service cost: Include seasonal coil cleaning, sensor verification, drain pan and heat trace checks, controls tuning, and technician callouts tied to poor defrost performance. These costs are often visible in winter PM work orders.
How to use the result
- Use it to compare defrost strategies, coil-cleanliness practices, and winter operating assumptions when evaluating real COP and annual cost.
- It does not directly calculate lost heating capacity during defrost or secondary production impacts from poor temperature control. Those effects may need a separate performance or downtime review.
Common questions
- What is the defrost energy cost calculator for? It estimates how much defrost operation costs for an air-source heat pump system, including both the electricity used during defrost and the related fixed service work.
- What information should I enter? Use defrost kWh from BAS or metering data, the applicable electricity rate, the portion of the season or fleet you are reviewing, and any fixed maintenance cost tied to defrost.
- What does the result tell me? The result shows whether defrost is a minor operating cost or a meaningful drag on project savings. It helps explain why a winter COP or energy bill may be worse than the design case.
- When is the result only an estimate? It is only an estimate when weather, humidity, coil cleanliness, or control logic are still uncertain. Sites with changing winter conditions can see defrost cost swing materially from year to year.
- What factors most affect this result? Outdoor temperature, humidity, coil surface condition, defrost control settings, and electric tariff usually drive the answer. If cost is high, review coil cleaning, sensor calibration, and defrost initiation logic first.
Last reviewed 2026-05-12.