CSLB C-20 HVAC ContractorHeating SystemsHard
A heat pump delivers 22,000 Btu/h of heating output while drawing 2,800 watts of electrical input. What is the approximate COP (coefficient of performance) of this unit?
- A3.1
- B4.5
- C1.8
- D2.3
Show answer & explanationAnswer & explanation
Correct answer: D. 2.3
Convert electrical input to Btu/h: 2,800 W × 3.412 Btu/Wh ≈ 9,554 Btu/h. COP = heat output ÷ electrical input in equivalent units = 22,000 ÷ 9,554 ≈ 2.3. This means the heat pump delivers about 2.3 times more heat energy than the electrical energy it consumes.
Why the other options are wrong
- A. 3.1 would require significantly higher output or lower wattage than given.
- B. 4.5 is unrealistically high for typical residential heat pump performance at this input.
- C. 1.8 would result from underestimating the output or overestimating the wattage conversion.
Coefficient of Performance (COP)
A ratio comparing a heat pump's heating output to its electrical energy input, both expressed in the same units, indicating heating efficiency.
- Formula: COP = heat output (Btu/h) ÷ (watts × 3.412)
- Typical residential heat pump COP ranges from 2.0 to 4.0
- Higher COP means more efficient heat delivery per unit of electricity
Memory trick: Watts times 3.412 gives Btu; divide output by that.