5 Bad Habits That Reduce Heat Pump Performance in Winter

Introduction

A modern inverter heat pump can deliver excellent performance even during Québec winters. Yet a large portion of winter service calls are caused not by mechanical issues, but by improper use or habits that go against how an inverter system is designed to operate.

Unlike traditional heating systems, a heat pump is not meant to run in short bursts. It is designed for continuous modulation that optimizes pressure, temperature, and airflow.

Below are the five most damaging habits for winter performance.

1. Setting the Indoor Fan to ON

This is the most common mistake in winter.

In ON mode, the fan runs continuously—even when the unit is not actively heating. The result:

• cooler air circulating through the home

• reduced comfort

• more frequent activation of auxiliary heating

• higher electrical consumption

Recommended mode: AUTO

This allows the unit to intelligently modulate airflow based on actual heating demand.

2. Changing the Thermostat Too Often or Too Quickly

An inverter heat pump performs best when indoor temperature remains stable.

Constantly adjusting the setpoint forces the compressor to ramp up unnecessarily, disrupts evaporation pressure, and significantly reduces energy efficiency.

Problematic behaviors include:

• raising the thermostat from 20 °C to 25 °C all at once

• lowering the temperature and raising it again an hour later

• adjusting the setpoint every 30 minutes

Best practice → Choose a comfortable temperature and keep it stable.

3. Allowing Snow to Accumulate Around the Outdoor Unit

As little as half a meter of snow around the unit can:

• block airflow

• increase internal pressure

• cause hard frost buildup

• reduce defrost effectiveness

• overload the compressor

A heat pump needs to breathe. Clearing 60 to 90 cm (24–36 in) around the outdoor unit is essential for proper defrosting, modulation, and heat exchange.

4. Neglecting the Indoor Air Filter

A clogged filter restricts airflow, leading to:

• reduced temperature differential (ΔT)

• lower heating capacity

• more frequent defrost cycles

• premature compressor wear

Winter is when the heat pump works the hardest—making a dirty filter its worst enemy.

Recommended frequency → Clean or replace the filter every 3 to 6 weeks, depending on usage.

5. Activating Auxiliary Heat Too Quickly

Auxiliary heating should only engage when truly necessary. Many users manually activate backup heat as soon as they feel slightly cooler air—often during a defrost cycle.

Consequences:

• significant energy overconsumption

• unnecessary cycling

• reduced compressor lifespan

• long-term performance loss

A modern heat pump, such as those from Willis, regains full heating capacity shortly after a defrost cycle. Letting the unit do its job is almost always the best option.

Conclusion

A heat pump is a highly intelligent system—but its efficiency also depends on homeowner behavior. By avoiding these five common mistakes, you improve:

• real heating capacity

• thermal stability

• perceived comfort

• energy consumption

• system lifespan

For installers, educating customers on these best practices dramatically reduces winter service calls—especially during humid cold periods when systems are under the greatest stress.