NRECA in conjunction with Alabama Electric Cooperative (AEC) tested three devices that aim to replace or reduce the use of strip heating. NRECA tested one hybrid heat pump and two electric thermal storage (ETS) systems. The testing is to determine the effect of the new technology on a co-op's load and what if any impact there is on a member's monthly bill.


Alabama Electric Cooperative attributes a recent shift in system peaking from summer to winter to a spike in electric resistance heat. A critical portion of the demand is traced to an unintended consequence of a successful G&T program—increased deployment of air source heat pumps with auxiliary strip heat. This discovery sparked an NRECA investigation into methods to flatten that peak through new efficiencies in the delivery of electric heat.


NRECA worked with AEC in turn recruited two of its member retail cooperatives, Coosa Valley Electric Cooperative (CVEC) and Covington Electric Cooperative (CEC), who provided test sites and field support.

At one test site an aging air-source heat pump was replaced with a hybrid heat pump. A hybrid heat pump is an air-source heat pump that has been modified so that it can draw heat from the earth under certain conditions. It uses two outdoor coils – an air-side coil and a geothermal loop.

At two additional test sites the existing heating systems were supplemented with ETS units. One test site had a heat pump; the other had centrally ducted electric resistance heat. ETS units use electric resistance elements to heat ceramic bricks. The bricks are heated with off-peak electricity, and the heat is transferred to the living space during on-peak hours. The main heating system is disabled during on-peak hours, so the ETS is the home's only heat source for a few hours.

NRECA issued a Request for Information to HVAC trade organizations, companies, and government and university research programs seeking technologies for testing. NRECA screened the responses to arrive at a list of candidate technologies. NRECA decided to pursue testing of two technologies. They are:

  • CoEnergies geohybrid heat pump
  • Steffes Electric Thermal Storage

Testing has been completed on the Steffes units. Another winter season of testing has been approved for the CoEnergies geohybrid heat pump. The results will be updated at the conclusion of the testing to include the additional results on the CoEnergies unit.


The final results of the ETS field tests and the preliminary results of the hybrid heat pump show measurable savings from both technologies. The data supports the assertion that electricity consumption is lowered during peak hours when either of the tested systems is used.

The results can be used by co-ops that experience winter peaks to get a jumpstart on exploring programs to eliminate those peaks. Co-ops can use the results to get up to speed on two different technologies and begin to assess what may work in their area. The report contains advice on the type of consumer that could be targeted for each of the technologies.


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Air-source heat pump, CoEnergies, cooling, electric heat, geohybrid, heat pumps, heating, load reduction, resistance heat, Steffes, thermal storage, White Dove, winter peaking