Part 3: Reading heat-pump efficiency and capacity ratings

That Energy Blog is published by Kates Energy Modelling Inc.

Updated October 1, 2026: Corrected capacity units, removed unreliable rating-conversion shortcuts, and clarified seasonal ratings, equipment matching and backup-heat decisions.

A heat pump can have a strong seasonal rating and still need backup heat on a cold day. The buying decision needs two checks: how much heat the equipment can deliver at the outdoor temperatures that matter, and how much electricity it needs to deliver that heat.

Capacity: how much heat can it supply?

Heating capacity is a rate. Use kW or Btu/h. One refrigeration ton equals 12,000 Btu/h, or about 3.517 kW. Energy over a period is measured in kWh: equipment delivering 3.517 kW steadily for an hour supplies 3.517 kWh of heat.

The model name or nominal tonnage does not tell you the available output at every temperature. Ask for the heating-capacity table for the exact equipment combination, including low-temperature performance. Compare it with the home’s design heat loss, rather than choosing from floor area alone.

Efficiency: keep the test conditions attached

COP describes heat delivered divided by electricity consumed at specified operating conditions. SEER2 describes seasonal cooling performance; HSPF2 describes seasonal heating performance. EER2 describes cooling efficiency at a specified test condition. ENERGY STAR defines these rating metrics and their test basis.

Compare like with like. HSPF and HSPF2, or SEER and SEER2, use different test procedures. A seasonal number also depends on its reference conditions; it is not a prediction of the COP on your coldest morning. The earlier article’s conversion shortcuts between EER and SEER, and between HSPF and a point COP, have been removed.

Three temperatures worth separating

Operating limit: the manufacturer’s permitted temperature range for the equipment. Being able to run does not establish that it can meet the full load.

Thermal balance point: the outdoor condition where the heat pump’s available output matches the building’s heat demand. Below that point, additional heat may be needed.

Economic balance point: the outdoor temperature at which the heat pump and alternative heat source have the same operating cost per unit of delivered heat, given electricity and fuel prices and equipment efficiencies. A dual-fuel system’s chosen changeover setting may also reflect comfort, capacity and equipment requirements.

NRCan’s Air-Source Heat Pump Sizing and Selection Guide explains selecting equipment against heating loads and performance data.

For the geeks

COP = delivered heat rate ÷ electrical input rate, with both rates in the same units. At a specified condition, 6 kW of heat from 2 kW of electricity gives COP = 3. This example describes one operating point.

Electricity needed ≈ heat needed ÷ COP over an interval for which that COP is representative. A seasonal estimate needs performance across the season, including relevant auxiliary and backup energy; do not apply one favourable point COP to the whole year.

Verify the complete system

The outdoor unit, indoor coil, blower and controls work together. An air handler and a furnace are not interchangeable names, although a compatible furnace blower may be part of a matched heat-pump system.

Ask the installer to identify the exact model numbers, the matched-system rating certificate, low-temperature capacity, required airflow and proposed backup controls. A certified rating describes a tested combination. Installation quality and actual operating conditions still determine the result in the house.

Use the ratings to narrow the choices. Use a heat-loss calculation, manufacturer data and a clear control plan to choose the system.