Counting Heat Pumps

Heat pumps present one of the best tools for decarbonization. They are very efficient compared to other heating technologies, are similar in price to air conditioning systems, and rely on an electric grid that is getting cleaner over time. Because of this, many states and regions, as well as the federal government, aggressively promote heat pumps and have set ambitious goals for their installation. Given the importance of these goals, accurate tracking of the number of heat pumps installed and their impacts is crucial. Therefore, it is very surprising to see the lack of consistency in reporting heat pump installations. For example, did you know that, since 2019, the Massachusetts program administrators have supported the installation of either 75,000, 95,000, or 264,000 heat pumps?

Heat Pump Installation in New England

Based in Massachusetts, I tend to follow energy-related news about other New England states. Maine recently made the news by blowing through their heat pump installation goals. Last summer, Maine announced that the state had surpassed its goal of 100,000 new heat pumps installed two years before its target year of 2025. Governor Mills subsequently made a new target of installing 175,000 more heat pumps by 2027. Around the same time, Massachusetts also made news, but for the opposite reason: the commonwealth had only met 30% of its state climate plan target of installing heat pumps in 100,000 homes by 2025. This seemed even worse because the population of Massachusetts is about five times that of Maine.

But how do the states really compare? Surprisingly, it turns out that states have different definitions of a heat pump installation. Massachusetts’ tracking is based on the number of homes in which a heat pump was installed. Maine tracks heat pumps based on installed capacity, with one heat pump equivalent to 25.1 MMBtus. Vermont, on the other hand, tracks heat pump installations based on the number of compressors installed. According to MassSave, the program administrators supported heat pump installations in 75,000 homes from 2019 to 2023, but this equates to the installation of nearly 96,000 heat pumps using the Vermont methodology and 264,000 using Maine’s approach.

How Others Track Installations

How does the HVAC industry count heat pumps? AHRI releases monthly heating and cooling shipment data for the US, which quantifies the number of heat pump units shipped by member manufacturers. However, it is not immediately clear how they define a unit. According to their definitions page, for split system heat pumps, manufacturers should only report those units “installed remotely from the indoor coil, air handler, or fan coil and require field connection of refrigerant lines.” I read this as AHRI counting a unit as the outdoor unit or compressor and that a multi-zone system with more than one indoor unit would count as a single unit.

Baseline studies provide a snapshot of different types of energy-using equipment currently installed in the market. These are used as foundational tools for program planning and estimating savings potential. When determining the number of heat pumps installed in a home, business, or market, evaluators typically count the heat pump systems by the number of outdoor units or compressors (i.e., approach used by Vermont and AHRI).

Why This Matters

Ultimately, how states define their targets (e.g., by homes, by units, by capacity) does not matter much as long as they track their progress over time consistently and correctly (and hopefully meet their goals). However, having an industry-standard approach will help all parties be able to roll up statistics across states to better quantify broader impacts. Standardized tracking also allows stakeholders and evaluators to compare progress across jurisdictions, to study the differences in adoption, and to try to replicate successes. After all, you can’t improve what you don’t measure.