Traditional air-source heat pumps can provide reliable heating when outdoor temperatures are moderately cold. However, once the weather reaches subzero temperatures, heat pumps suffer a drastic loss of performance due to frost accumulation on their outdoor units.

• Many heat pumps are equipped with a defrosting function, but they cannot provide indoor heating while the defrosting cycle is running.
• As outdoor temperatures drop, the heat pump spends more time defrosting and its overall heating output is decreased.

Cold climate heat pumps have design features that reduce the need for frequent defrosting. These include built-in heaters for their outdoor units, which prevent ice and snow accumulation. Even if outdoor temperatures have dropped below 0°C (32°F), cold climate heat pumps can operate continuously. Some HVAC manufacturers now offer heat pumps capable of operating at temperatures as low as -26°C (-15°F).

The Residential Cold Climate Heat Pump Challenge was launched in 2021 as a partnership between Natural Resources Canada (NRCan), the U.S. Department of Energy (DOE), and the U.S. Environmental Protection Agency (EPA). This Challenge is part of the Initiative for Better Energy, Emissions, and Equity (E3).

The Challenge has the goal of improving cold climate heat pump technology while reducing its environmental footprint. The Challenge is divided into two segments:

• Designing a cold climate heat pump optimized for -15°C (5°F)
• Designing a cold climate heat pump optimized for -26°C (-15°F)

Ten HVAC manufacturers joined the challenge: Bosch, Carrier, Daikin, Johnson Controls, Lennox, LG, Midea , Mitsubishi, Electric, Rheem, and Trane Technologies. They are working to develop heat pump models that meet the technical specifications established by NRCan, U.S. DOE, and US EPA. Many local governments and utility companies are also participating, and they will help implement the high-efficiency heat pumps developed during the Challenge.

Cold Climate Heat Pump Challenge: Main Requirements

The CCHP Challenge has general requirements for all heat pumps designs that participate, which apply in both segments:

• The heat pump must be designed for residential use, centrally ducted and fully electric.
• The unit must have a nominal cooling capacity between 24,000 and 65,000 BTU/h. In the case of heating-only heat pumps, this requirement applies for the heating capacity.
• The unit must meet all federal and local standards that apply for heat pump technology.
• The unit must use a refrigerant with a GWP of no more than 750, measured according to ASHRAE requirements.

The Challenge establishes minimum efficiency requirements. Each heat pump must meet a minimum Heating Seasonal Performance Factor (HSPF2), which is determined individually according to its type and capacity. The Residential Cold-Climate Heat Pump Technology Challenge Specification has a detailed explanation of the HSPF2 measurement procedure.

• Under Canadian energy efficiency standards, for example, central heat pumps below 65,000 BTU/h are required to have a minimum HSPF between 4.9 and 6.0 (depending on their type).
• The CCHP Challenge will deliver heat pumps with HSPF2 efficiency values above 8.5, exceeding current standards.
• The exact efficiency requirements will vary for each heat pump design, depending on its features and testing results.

To demonstrate their performance, heat pumps must be tested according to the procedures described in Appendix A of the CCHP Challenge technical requirements. The document specifies four testing procedures, designed to validate heat pump performance at different outdoor temperatures:

• Min/Mild Test = Performance at 47°F (8.33°C) outdoor temperature
• H2_RH Test = Performance at 35°F (1.67°C) outdoor temperature
• H4_Max/Cold Test = Performance at 5°F (-15.00°C) outdoor temperature
• Max/Extreme Test = Performance at -15°F (-26.11°C) outdoor temperature

The testing requirements vary depending on the section of the Challenge. Heat pump designs optimized for -15°C only require the first three tests, while the -26°C test is optional. On the other hand, heat pumps optimized for -26°C must be subject to all four tests. The minimum HSPF2 efficiency required for cold-climate heat pumps is determined based on their type, capacity and the results of these tests.

Depending on their size, the cold climate heat pumps participating in the Challenge may be required to have two or more heating stages. The following table summarizes this requirement:

The heat pumps participating in the Challenge must also meet connectivity requirements according to energy Star Product Specification for Central Air Conditioner and Heat Pump Version 6.0:

• Section 3C - Installation Capabilities
• Section 4B - Communications
• Section 4C - Customer Feedback
• Section 4D - Demand Response

CCHP Challenge: Requirements for the 5°F (-15°C) Segment

In addition to the general conditions described in the previous section, heat pumps participating in the -15°C segment must meet the following efficiency requirements:

The compressor units of heat pumps operating in the -15°C segment must also meet the following operating requirements:

• Low-temperature compressor cut-out no higher than -23°C.
• Low-temperature compressor cut-in no higher than -21°C.

CCHPs participating in the -15°C segment are subject to three tests, as previously mentioned: Min/Mild (47°F/8.33°C), H2_RH (35°F/1.67°C), and H4_Max/Cold (5°F/-15°C). The Extreme/Max test at -15°F (-26.11°C) is optional in this segment of the challenge.

CCHP Challenge: Requirements for the -15°F (-26°C) Segment

Heat pump designs participating in the -26°C challenge must meet all the requirements of the -15°C segment, including the minimum COP values in the table above. However, their compressor operating requirements are different:

• Low-temperature compressor cut-out no higher than -29°C.
• Low-temperature compressor cut-in no higher than -26°C.

Heat pumps optimized for -26°C must complete all four tests described in the CCHP Challenge technical document, including the Extreme/Max test at -15°F (-26.11°C). Alternatively, they can follow an interpolation method that uses the H4_Max/Cold test results and only the heat pump power input value of the Extreme/Max test.

Savings of a High-Efficiency CCHP Potential

According to the Challenge timeline, the high-efficiency heat pumps that meet the technical requirements described above could reach the market by 2024:

• Product Prototypes = Late 2021 / Early 2022
• Lab Testing = 2022
• Field Testing = Winter 2022-2023 and Winter 2023-2024
• Deployment Programs and Commercialization = 2024

As a quick example of the savings potential, assume you currently own a heat pump with an HSPF2 of 6.0, which consumes 5,000 kWh per year. At Canada’s average electricity price of 15.5 cents/kWh, the annual operating cost is CA$775.

Considering a consumption of 5,000 kWh/year and an HSPF2 of 6.0, this heat pump delivers an estimated heating output of 30 million BTU/year. If you upgrade to a new heat pump that meets the CCHP challenge requirements, with an HSPF2 of 9.0, you achieve the same heating effect with a much lower kWh consumption:

• Estimated kWh input = Heating Output / HSPF2
• Estimated kWh input = 30 million BTU / 9.0 = 3,333,333 watt-hours = 3,333 kWh
• Estimated operating cost = 3,333 kWh x CA$0.155/kWh = CA$517

In this example, you are getting the same heating output while saving 1,667 kWh/year. This represents energy savings of CA$258 per year.

The potential savings are even higher if you compare a high-efficiency heat pump with an electric resistance heater. To deliver 30 million BTU, a resistance heater must consume around 8,800 kWh at a cost of CA$1,364. In this case, a 9.0 HSPF2 heat pump with an annual consumption of 3,333 kWh saves around CA$847 per year.