The Massachusetts Residential Retail Program offers rebates for residential customers to install HPs for heating and cooling through the Mass Save® program. The program offers rebates for ducted and ductless air source heat pumps (ASHPs) for both whole-home and partial-home displacement projects. Whole-home rebates require customers use HPs for heat and remove their pre-existing or legacy heating system (or use it only when the HPs are down for service or repair). Partial-home rebates allow customers to keep their pre-existing heating system but require ICs to allow switching between the HPs and pre-existing system.
The program is designed to motivate customers to reduce greenhouse gas (GHG) emissions from fossil fuel heating sources by using a more efficient HP to provide a majority of the home’s space heating needs. For partial-home displacements, the program requires ICs to encourage customers to prioritize the use of HPs for heating and reduce usage of their legacy fossil fuel heating systems.
The study focuses on understanding IC systems in partial displacement scenarios in single-family homes with mini-split HP systems. A previous evaluation, the Energy Optimization Fuel Displacement Impact and Process Study, found that homeowners who received mini-split systems with ICs often experienced more challenges with the IC system than those with central HP systems. This follow-up study focuses on topics related to mini-split IC technologies and how contractors and customers experience them. While researching the technical aspects of ICs, the study team also learned more broadly about system configuration and use cases and how they support program goals to reduce/displace fossil fuel usage. The findings and recommendations therefore span the research topics broached in the prior study, as well as broader issues around configuration and use cases.
This report presents findings from follow-up research conducted on integrated controls (ICs) used with ductless mini-split heat pumps (HPs). These dual-fuel coordination systems were installed through the electrification sub-offering of the Massachusetts Residential Retail Program.