A good COP for heat pump units starts at about 2.0 for an air source heat pump and about 3.1 for geothermal, but heat pump COP can be well above 4.0 too, as seen in the chart below. A geothermal heat pump is also called a ground source heat pump.
This guide includes the definition of coefficient of performance, and explanation of its practical meaning and answers to the question: What is a good COP for heat pump units of various types.
What is a Good COP for Heat Pump Units?
This chart shows various heat pump types. It includes a minimum coefficient of performance for various heat pump types. A second column shows good COP for heat pump models.
The minimum requirements are included in the 42 U.S. Code § 6313 – Standards.
Type (HP = Heat Pump)
Air Source HP (1)
Closed Loop HP (2)
3.1 - 3.6
3.5 - 4.2
Open Loop HP
3.5 - 4.1
4.0 - 4.5
Direct Exchange HP
(1) COP is not used as an efficiency rating for air source heat pumps. Instead, they have minimum SEER (cooling) ratings of 13 in the northern US and 14 in the Southern US. They have minimum HSPF (heating) ratings of 8.5.
(2) Geothermal heat pumps are further broken down by the type of loop and water-to-air vs water-to-water. All the data is found on this Energy.gov page.
We add a “+” to the Most Efficient numbers because geothermal heat pump efficiency improves each year.
Now, let’s move on to a definition of heat pump COP and related issues.
Definition of Coefficient of Performance
There are very good technical, in-depth articles about COP out there like this one.
This guide attempts to take a technical measurement and make it accessible to all our readers.
A good practical definition of coefficient of performance is:
COP is a measurement of how effectively a heat pump uses electricity to move heat from place to place. Specifically, the coefficient of performance of heat pump units is the ratio of the heating and AC output (how much heating and cooling it delivers) to the energy used to power the heat pump.
In short, COP measures how much heat energy is moved compared to how much is used.
For example, an air source heat pump with a coefficient of performance of 2.5 moves 2.5 times more heat energy than the energy used to move it.
Calculating Heat Pump COP
How is coefficient of performance calculated? Simply put, COP equals the amount of energy produced (energy out) divided by energy used (energy in).
COP = Energy Out/Energy In
The energy out – the amount of heat moved by the heat pump – is measured in BTU/h, or British Thermal Units per hour.
The energy in is measured in watts.
COP = BTUs/Watts
Example of Calculating Heat Pump COP
Here are the steps to determining the COP of heat pump models. The information needed can be found in the heat pump’s manual or online.
1). Determine the output of the unit – it’s size or capacity to heat and air condition.
Let’s say a geothermal heat pump’s output is 60,000 BTU/h, also called a 5 ton heat pump, as 12,000 BTUs = 1 ton of heating or cooling power. Note: The /h is often dropped. It is understood that the BTU output is per hour.
2). Know how much energy it uses in watts.
A typical 60,000 BTU geothermal heat pump runs on about 4,200 watts.
3). Multiply BTU/h by 0.293 because one BTU = 0.293 watts.
1 BTU = .293 watts is not a ratio. It is a conversion or comparison. It says nothing about efficiency. That’s the next step – determining heat pump COP, a measure of how efficiently it uses electricity for heating and air conditioning.
So, 60,000 x 0.293 = 17,580
An average geothermal heat pump from WaterFurnace or other leading brand with 60K BTU/h capacity produces or outputs 17,580 watts of energy. It moves the energy from indoors to outdoors or the other way around depending on which it is in, AC or Heat.
4). Divide watts of output by watts of energy used to create the output. This is the coefficient of performance of the heat pump.
17,580 / 4,200 = 4.18 COP
What does that mean? For every watt of energy the heat pump uses, it moves more than 4 watts of heat energy into or out of the home.
If we were to compare that 4.18 COP to the efficiency of the high-efficiency furnaces mentioned above, it would be like saying this heat pump is 418% efficient compared to 98.7% or 98.5% for the furnaces.
That’s pretty amazing!
Heat Pump Efficiency – How Can COP Be so High?
The most efficient gas furnaces from top brands like the Lennox SLP98V (98.7% AFUE) and the Carrier Infinity 98 (98.5%) are extremely efficient. But those percentages are less than 100, meaning they have a coefficient of performance of less than 1!
Coefficient of Performance Factors
There are several factors that affect heat pump coefficient of performance:
- Type: Geothermal heat pumps are more efficient than air-source heat pumps. A geothermal model collects heat in winter and dumps heat in summer in the ground (geo) or water. An air source does the same in outside air. Because the temperature in the ground is warmer in winter and cooler in summer than the air is, a geothermal heat pump has a much easier time collecting and dumping heat.
- Geothermal Loop Type: Typically, open loop water-to-air heat pumps have the highest COP. Closed loop water-to-air heat pumps are average, and closed loop water-to-water heat pumps have the lowest COP.
- Heating or Air Conditioning: Most geothermal heat pumps have a higher COP in cooling mode than when heating.
- Running on Low or High Stage: Many geothermal heat pumps have 2-stage compressors. They use less energy on the lower stage, which is about 65% of capacity. The heat pump COP is higher on Low.
- How Hot or Cold it is Outside: Called ambient temperature, the outdoor temperature plays a significant role. For example, if the heat pump is air conditioning your home, and it is 80 degrees F outside and 70 inside, that’s just a 10 degree difference. Dispersing the heat in 80 degrees is relatively easy. If it is 110 outside, the heat pump must work harder to get rid of heat at that temperature. Conversely, the heat pump must work harder the colder it is outside when in Heat mode.
This graph shows the impact of outside temperature on COP in air conditioning mode.
How can heat pumps have a COP of 2 to 4 or higher?
Heat pumps don’t create heat in the same way a space heater, gas furnace or boiler does. Instead, they use a compressor that creates a pressure imbalance between one side of the unit and the other. The imbalance causes refrigerant in the lines to move to equalization, and that causes the flow of refrigerant.
- In AC mode, the refrigerant picks up heat indoors and dumps it outside.
- In heat mode, heat energy is collected outdoors and pumped indoors to heat your home or business.
Heat Pump COP Compared to Other HVAC
This brief chart shows how much it costs to operate a heat pump compared with other electric units in a cold climate. The image below includes other types.
Air Source Heat Pump
Geothermal Heat Pump
This diagram courtesy of manufacturer Nordic Geothermal Heat Pumps is a comparison of average energy costs of the most popular heating systems.
There is a lot of money to be saved in operating costs with a heat pump, but they can be more expensive, especially geothermal heat pumps. Costs, brand reviews and more can be found on PickHVAC starting with our 2020 Geothermal Heat Pump Costs and Guide.