Heat Pump Efficiency
Heat-pump efficiency cannot be summarized by one number.
For current U.S. residential equipment, the main metrics are:
- SEER2 for seasonal cooling efficiency
- HSPF2 for seasonal heating efficiency
- EER2 for cooling efficiency at a specified test condition
- COP for heating efficiency at a specific operating condition
The right metric depends on the question you are trying to answer.
Source: ENERGY STAR Heat Pump Criteria
Heat Pump Efficiency Metrics Compared
| Metric | Mode | What it describes |
|---|---|---|
| SEER2 | Cooling | Seasonal cooling output divided by seasonal electricity input |
| HSPF2 | Heating | Seasonal heating output divided by seasonal electricity input |
| EER2 | Cooling | Cooling output vs. electric input at a defined test condition |
| COP | Heating | Heat output divided by electric input at a defined operating condition |
A high HSPF2 does not tell you the exact COP at 5°F.
A strong 5°F COP does not tell you the full seasonal heating performance.
You need the metric that matches the decision.
What Is SEER2?
SEER2 is the current seasonal cooling-efficiency rating used for residential central air conditioners and heat pumps under the newer DOE test procedure.
ENERGY STAR defines it as total heat removed over the cooling season divided by total electrical energy consumed over that season.
What Is HSPF2?
HSPF2 is the current seasonal heating-efficiency rating for air-source heat pumps.
It represents seasonal space heating delivered divided by total electrical energy consumed under the defined test procedure.
What Is COP?
COP is a dimensionless ratio:
heat delivered ÷ electrical energy input
A COP of 3 means the system is delivering three units of heat per unit of electrical energy at that operating condition.
COP is especially useful for understanding cold-weather performance because it can be reported at specific temperatures.
Current ENERGY STAR Cold Climate qualification requires a COP of at least 1.75 at 5°F.
Source: ENERGY STAR Heat Pump Criteria
Why Can a Heat Pump Be More Than 100% Efficient?
The phrase "300% efficient" is shorthand that can confuse more than it helps.
A heat pump is not converting electricity into three times as much energy.
It uses electricity to move existing heat.
That is why delivered heat can exceed electrical input on a one-to-one energy basis.
DOE explains heat pumps as systems that transfer heat rather than generate it directly.
Source: DOE — Pump Up Your Savings with Heat Pumps
What Is a Good SEER2 and HSPF2?
For standard ENERGY STAR residential split heat pumps, the minimum criteria are:
| Metric | Standard ENERGY STAR split heat pump |
|---|---|
| SEER2 | 15.2+ |
| EER2 | 11.0+ |
| HSPF2 | 7.8+ |
Cold Climate split systems use separate criteria that include low-temperature performance.
Ducted Cold Climate equipment requires at least 8.1 HSPF2, while non-ducted equipment requires at least 8.5 HSPF2.
Source: ENERGY STAR Heat Pump Criteria
Higher is not automatically the best economic purchase.
Why Does Heat Pump Efficiency Drop in Cold Weather?
As outdoor air gets colder, an air-source heat pump has a more difficult temperature lift to perform.
Capacity and COP can decline.
Defrost also consumes energy.
Modern cold-climate systems mitigate those effects with improved compressors, controls, heat exchangers, and system design, but the physics does not disappear.
Cold-weather heat pump efficiency
How Much Electricity Does a Heat Pump Use?
Electricity use depends on:
- building load
- system COP/efficiency
- outdoor temperature
- thermostat settings
- runtime
- duct losses
- backup heat
- local climate
A 36,000-Btu/h heating output at COP 3 requires roughly 3.52 kW of electrical input at that operating point.
That is a point-in-time example, not annual consumption.
Does Higher Efficiency Always Save Money?
No.
Higher efficiency reduces energy input for the same delivered load, but the economic value depends on:
- equipment price premium
- local electricity rate
- climate
- annual heating/cooling load
- ownership period
- maintenance
- rebates
A premium heat pump can be technically more efficient and financially worse.
Compare total cost of ownership.
What Matters Beyond the Rating?
Real performance is affected by:
- correct sizing
- ductwork
- refrigerant charge
- airflow
- controls
- installation quality
- backup-heat settings
- building envelope
An 18 SEER2 system installed badly can be a worse asset than a lower-rated system installed and commissioned correctly.
How Should You Compare Heat Pump Efficiency?
Use:
Cooling-dominated climate: prioritize SEER2/EER2, sizing, humidity control, and part-load behavior.
Heating-dominated climate: prioritize HSPF2, low-temperature COP/capacity, and backup strategy.
Mixed climate: evaluate both.
Then compare complete installed price.
Review the equipment shortlist using the ratings and installed prices relevant to your home.
Compare Efficient Heat Pump Systems
Ask contractors to quote properly sized systems and show both seasonal ratings and low-temperature performance where relevant.
Prepare for installer conversations
Check the design process and compare written scopes, equipment matches, and installed costs.