“Just Right” Heat Pumps: Why Sizing Matters in Cold Climates

You’ve heard all about heat pumps – they're in the news more than ever lately and are being installed in more homes than ever. In fact, nine states (including six states in NEEP’s region) recently set ambitious goals for 90 percent of all residential heating, air conditioning and water heating sales to be heat pumps by 2040. 

To meet these goals, states must make substantial commitments to support contractors in workforce development and training, as well as bolster consumer demand through education, incentives, and technical assistance. Heat pump technology has proven itself to efficiently and effectively heat and cool homes across the Northeast and beyond, but these results depend on a very important factor: sizing. 

System performance, comfort, and energy efficiency can be significantly impacted by poor sizing and system selection. This means that to use heat pumps to accelerate a just and clean energy transition, we must get sizing and system selection right. NEEP has released a new and improved Sizing Tool V2.0 with the help of regional stakeholders, including TRC and Clearly Energy who helped build these tools from scratch and continue to improve them, to support best sizing practices. 

The tools have several updated features, including side-by-side product comparison, multi-product system visualization to view how multiple units stack up to meet a home’s needs, and cooling performance visualization. To explore the ccASHP sizing support tools, check out our new user guide.

Why Sizing Matters

Variable speed heat pumps adjust how much heating or cooling they provide depending on outdoor temperature and the indoor temperature selected by the homeowner. Based on this, variable speed heat pumps ramp up or down depending on the needs of a space. Matching a home’s specific heating load with a right-sized heat pump will maximize efficiency, comfort, and value.

If a heat pump is too small for a space, it will struggle to provide sufficient heat during the coldest winter days. You’ll need to turn on a back-up heat source, which reduces the emissions and monetary savings you counted on in buying your heat pump. You sacrifice comfort and efficiency when a heat pump is “undersized.” To avoid this, contractors may overcompensate and install a unit that is too big for a space. However, “oversizing” can lead to excessive cycling, low efficiency, and ineffective summer dehumidification. 

This makes right-sizing important for high efficiency, performance, and customer satisfaction. 

Learn more about sizing and selecting ccASHPs here. NEEP works across the region to determine best sizing practices and has created tools and resources to support this.

How NEEP’s Sizing Tools Help

NEEP offers cold climate heat pump sizing tools, embedded in NEEP’s Cold Climate Air Source Heat Pump list, to help users select cold climate air source heat pump (ccASHP) products that are sized to best match the peak and annual heating needs of a home or heating zone. Because the tool takes advantage of the additional performance data in the ccASHP list, the visuals and calculations show how a specific heat pump’s capacity matches the heating and cooling loads across a home’s seasonal temperatures.

Caption: Product Comparison View https://ashp.neep.org/

Contractors can use these tools to find the “just right” heat pump unit(s) for any customer depending on their location, heating design load (Btu/h), and optional cooling design load. 

How Programs can Support Better Sizing Practices

With states and utilities taking action to achieve ambitious climate and energy goals while balancing customer protection against unaffordable energy bills, sizing of heat pumps matters. Programs also need to ensure customer satisfaction through improved comfort. Energy efficiency programs promoting the adoption of heat pumps use a variety of tools and resources to ensure best practices. 

Here are some ways programs can ensure energy efficiency savings through proper sizing:

• Require contractor network to participate in heat pump design/sizing training through manufacturer, distributor, or energy efficiency programs 
• Include “size for heating” instruction in trainings delivered to contractors
• Include the NEEP sizing tool along with other tools and resources in contractor training 
• Include sizing-for-heating requirements for highest tier of equipment rebates (i.e. 90-120 percent of heating load must be met)
• Require contractors to develop heating/cooling load calculations via ACCA Manual J (or approved tools)
• Provide ongoing technical assistance and support for contractors
• Implement post-installation quality assurance processes

Hear more about how programs are supporting best practices for sizing in our March webinar, Sizing Matters: Air Source Heat Pumps where we learned from program administrators and implementers how they’re approaching the issue of sizing.

Join us again in April for our second webinar in this series all about how to use the NEEP ccASHP sizing tool, including highlights of new features and specific use-cases.