How to set your heat pump for winter: mode, temperature and baseboards

In short: in winter, leave your heat pump running in Heating mode (not Auto), at a steady temperature, and set your baseboard heaters 2 to 3°C lower so they only serve as backup. A few simple settings are enough to let the heat pump do most of the work.

Every fall, we hear the same questions: should I turn the heat pump off when it gets really cold? Should I turn the temperature down at night? Why does the air feel lukewarm? Here are the settings recommended by Hydro-Québec and Natural Resources Canada (NRCan), with our explanations and a few tips from our technicians.

1. Choose Heating mode, not Auto

Auto mode looks convenient: the unit switches between heating and cooling on its own. But in winter, it can start cooling on a mild, sunny day or when a fire is warming the house. That's why Hydro-Québec recommends selecting Heating mode all winter, then Cooling mode in summer.

2. Leave it running all winter

Turning the heat pump off when it's cold and heating only with baseboards is a mistake, according to Hydro-Québec: a heat pump uses up to three times less electricity than baseboard heaters for the same amount of heat. Turning it off simply makes the baseboards work harder.

And our winters are often milder than we think: Hydro-Québec points out that southern and central Québec average fewer than 15 days below -20°C per winter. The rest of the time, the heat pump can do much of the work. When it's colder than your model can handle, the backup heat takes over; that's normal.

3. Find your temperature and leave it alone

A heat pump runs more efficiently at a constant temperature. Every time you raise or lower the setting, the unit has to work harder to reach it, and those repeated adjustments put needless strain on it, Hydro-Québec explains. Pick a comfortable temperature (Hydro-Québec uses 21°C as an example), then leave it.

The number on the heat pump is just a setting

A tip from our technicians: your heat pump doesn't read the temperature in the same place as your baseboard thermostat. It measures it higher up, at the indoor unit mounted high on the wall. So it's normal to see a degree or two of difference between the baseboard thermostat and the heat pump setting.

The number on the display is just a setting: some people are comfortable at 24°C on the heat pump, others at 20°C. Aim for your comfort, not a specific number. To find the right setting, adjust one degree at a time, give it 24 hours so the house can settle, then see whether you're comfortable or not. Once you've found your setting, leave it alone.

What about at night?

Heat pumps respond more slowly than traditional heating systems to large temperature changes. NRCan therefore recommends lowering the setting by no more than 2°C, or using a "smart" thermostat that starts heating back up ahead of time. A bigger drop can make the baseboards kick in the next morning to catch up, which cancels out part of the savings.

4. Set your baseboards 2 to 3°C lower

This is the setting that makes the biggest difference in an electrically heated home. If the baseboards are set to the same temperature as the heat pump (or higher), they heat at the same time and you lose a good part of the savings.

Hydro-Québec and NRCan recommend setting the baseboard thermostats 2 to 3°C below the heat pump setting. For example, heat pump at 21°C and baseboards at 18 or 19°C. The baseboards then only come on when the heat pump can't keep up, during cold snaps.

Keep in mind that the baseboard thermostat and the heat pump don't read the temperature in the same place (see above): the 2 to 3°C gap is a starting point. What matters is that the baseboards stay set a bit lower than the heat pump, so they only serve as backup.

During Hydro-Québec peak-demand events, if you have a wall-mounted heat pump, Hydro-Québec suggests lowering the baseboard settings, especially in unoccupied rooms, to stay comfortable where you are.

5. Fan and louvres: small settings that help

• Louvres pointing down: for a wall-mounted unit, most manufacturers recommend directing the air downward in heating mode, NRCan notes. Warm air rises naturally; blowing it toward the floor warms the room better.
• Fan on Auto or high: NRCan recommends these settings in heating mode to get the most heat out of the heat pump. If the noise bothers you at night, Auto is a good compromise.
• Let the air circulate: aim the airflow toward open areas and keep doors open so the heat reaches other rooms. Don't block the indoor unit with furniture or curtains.
• Use the sun: open the curtains on the sunny side during the day and close them in the evening to keep the heat in.

Why does the air from my heat pump feel lukewarm?

That's normal. A heat pump delivers a lot of air at a lower temperature than a furnace: normally between 25 and 45°C, compared with 55 to 60°C for a traditional heating system, according to NRCan. If you hold your hand in front of the unit, the air may feel less hot, even though the room stays comfortable.

The indoor unit may also stop blowing for a few minutes in cold, humid weather: that's the outdoor unit's defrost cycle. It's part of normal operation. To learn what to watch for (ice that never melts, snow around the outdoor unit), see our 8 winter maintenance tips (in French).

The right settings at a glance

Settings not enough? Think maintenance

Even with the right settings, a heat pump with dirty filters heats less well. Hydro-Québec says a clogged filter can reduce a heating system's efficiency by 10 to 30%. Keep your filters clean (see our article on cleaning heat pump filters) and have the unit inspected every year, ideally in the fall.

If your heat pump blows cold air in Heating mode (outside of defrost), makes unusual noises, or your baseboards seem to be doing all the work even in mild weather, have it checked by a technician.

Sources

• Hydro-Québec, Using your heat pump in winter.
• Hydro-Québec, Heat pumps: Seven ways to save year-round.
• Natural Resources Canada, Heating and Cooling With a Heat Pump (Operation and Air-source heat pumps sections).