Heat Pump Evaluation
Heat pump performance evaluation including COP and HSPF metrics, balance point calculation, defrost cycle assessment, auxiliary heat staging, and cold-climate heat pump technology.
- Calculate and interpret Coefficient of Performance (COP) for heat pumps
- Determine the balance point and supplemental heat requirements
- Evaluate defrost cycle operation and its impact on heating performance
- Assess auxiliary heat staging and switchover settings
Lección 1
Heat Pump Fundamentals & COP
How Heat Pumps Differ from AC Systems
A heat pump is an air conditioning system that can reverse its refrigeration cycle to provide heating. In cooling mode, it absorbs heat from indoor air and rejects it outdoors - exactly like a standard AC system. In heating mode, it reverses the flow (using a reversing valve) to absorb heat from outdoor air and deliver it indoors.
The key advantage of a heat pump is efficiency. A gas furnace converts fuel to heat at 80-98% efficiency - one BTU of gas input produces 0.80 to 0.98 BTU of heat output. A heat pump does not create heat; it moves it. For every BTU of electrical energy consumed, a heat pump can move 2-4 BTU of heat from the outdoor air into the building. This makes heat pumps 200-400% efficient in terms of energy conversion.
Coefficient of Performance (COP)
COP is the ratio of heating (or cooling) output to electrical input, measured at a single operating condition:
COP = Heating Output (BTU/h) / Electrical Input (BTU/h)
Since 1 watt = 3.412 BTU/h, you can also calculate: COP = Heating Output (BTU/h) / (Watts x 3.412)
At 47 F outdoor (the AHRI rating condition), a typical heat pump has a COP of 3.0-4.0, meaning it delivers 3 to 4 BTU of heat for every BTU of electricity consumed. But COP drops as outdoor temperature drops because there is less heat energy available in colder air. At 17 F outdoor, COP might drop to 2.0-2.5. At 0 F, it might be 1.5-2.0.
For comparison, electric resistance heat always has a COP of 1.0 - one BTU of electricity produces one BTU of heat. A heat pump is beneficial as long as its COP exceeds 1.0, which is the case even at very low temperatures for modern equipment.
HSPF2 - Seasonal Heating Efficiency
While COP measures efficiency at a single condition, HSPF2 (Heating Seasonal Performance Factor) measures the average efficiency over an entire heating season, accounting for varying outdoor temperatures, defrost cycles, and supplemental heat usage:
HSPF2 = Total Seasonal Heating Output (BTU) / Total Seasonal Electrical Input (Wh)
A higher HSPF2 means lower annual heating costs. The federal minimum is 7.5 HSPF2. ENERGY STAR heat pumps require 8.1+ HSPF2. Premium cold-climate heat pumps achieve 10-12 HSPF2.
| HSPF2 Rating | Classification | Annual Heating Cost (3-ton, Zone 4) |
|---|---|---|
| 7.5 | Federal minimum | ~$1,200 |
| 8.5 | Good | ~$1,060 |
| 10.0 | Excellent | ~$900 |
| 12.0 | Premium (cold-climate) | ~$750 |
(Costs approximate at $0.14/kWh for illustrative purposes)
Heat pumps move heat rather than creating it, achieving COPs of 2-4 (200-400% effective efficiency). COP decreases as outdoor temperature drops but remains above 1.0 even at very cold temperatures. HSPF2 measures seasonal heating efficiency including defrost and supplemental heat. The federal minimum is 7.5 HSPF2. BPI professionals must evaluate heat pump COP at the actual outdoor temperature during assessment.