The most common corrective action issued to Residential trade allies for heat pump and heat pump control projects is failure to program correct auxiliary heat lockout settings. Missing this simple step leads to reduced comfort and savings for customers, along with costly return visits to make corrections.

Advancements in heat pump technology are delivering far more energy-efficient equipment than ever before to heat and cool our homes. Heat pumps can reliably provide heating when outdoor temperatures are well below freezing. When in operation, auxiliary backup heating relies on electric resistance heat strips, which draw substantially more energy than heat pump technology, resulting in elevated utility costs when in use.

The lockout temperature in the installer settings of the heat pump controller (thermostat) prevents the auxiliary backup heating kit in the air handler from being activated if outdoor temperatures are above the programmed lockout setting threshold. Energy Trust’s 2025 Specifications Manual states, “HC 1.1 – Lockout Temperature: The heat pump control shall have the ability to lock out supplemental/auxiliary electric furnace heat at 35°F. The lockout temperature shall be set at or below 35°F.” Energy Trust recommends that the lockout is set to no greater than 25°F for extended capacity systems.

Adhering to Energy Trust lockout setting guidelines during installation of heat pump systems maximizes their impact on comfort and affordability for customers and ensures greater energy savings for the communities we serve.

Due to the high volume of issues Energy Trust sees surrounding heat pump lockouts, field staff will no longer correct settings in the field. Instead, contractors will be required to return so they can make corrections and document them.

If you have questions, please call the Energy Trust Residential Trade Ally team at 866.365.3536.