Emera Maine Heat Pump Study

Case Study

Emera Maine Heat Pump Pilot Program

Emera Maine provides electricity to Maine residents. They designed a program to study the efficacy and performance of ductless heat pumps, also known as “mini-split” heat pumps, in selected homes in their service area. To motivate customers, they provided each participant a $600 rebate and on-bill financing of the heat pumps. Emera turned to PowerWise to provide the most accurate circuit-level metering equipment.

Energy Use Patterns

According to the project report by EMI Consulting, the in-home SiteSage circuit-level electricity meters “allowed the research team to isolate the usage of the installed heat pump and generate a pattern of electric usage after the installation of the heat pump. In addition, the research team used these monitors to model usage of primary heating sources (e.g., furnaces, boilers).”

How Heat Pumps Work

The main portion of the heat pump is outside, and the indoor distribution unit is a small heat exchanger, mounted high on a wall. In heating mode, heat is drawn from surrounding outdoor air and transferred by means of a fluid to the distribution unit inside on the wall. The fluid flows through a heat exchange unit, transferring heat to the air, and a fan blows the heated air into the living space. In cooling mode, the cycle is reversed. The main outside unit draws heat from the fluid and transfers it to the surrounding outdoor air, cooling the fluid. The indoor distribution unit uses the cooled fluid to cool the indoor air, circulating it into the living space.

The important factors in the process are:

• outdoor temperature
• temperature of the air flowing from the distribution unit indoors
• temperature of the living space
• the energy used by the fans and condensers of the heat pump.

Electricity Monitoring Equipment

PowerWise instrumentation measured these to a high standard of accuracy and reliability.

The data quality created by the SiteSage energy management system provided by PowerWise is a strong foundation for this and many other studies. Results of the study suggested that ductless heat pumps are a cost-effective way to heat homes in the North Temperate climate of Maine, which extends across nearly half the area of the contiguous United States.

The study may impact both the use and recommendation of heat pumps in homes heating with conventional oil or electric heat, and could have a long-term impact on energy use and energy policy in the state.

Read the published report.