Your heat pump and Hydro-Québec peak hours: staying warm while paying less this winter

In short: from December 1 to March 31, Hydro-Québec can call peak events in the morning (6 to 10 a.m.) or late in the day (4 to 8 p.m.), mostly when it's very cold. To help the grid and, if you're on the Flex D rate, lower your bill: pre-heat the house a few hours before, turn the heat down at least 2 °C when the event starts, lower the baseboards in empty rooms first, and let your heat pump do most of the work.

With winter on its way, many customers ask us what to do with their heat pump when Hydro-Québec announces a peak event. Should you turn it off? Turn it down? And is the Flex D rate worth it? Here's what Hydro-Québec says, and how to apply it when you heat with a heat pump and baseboards.

What are peak hours?

A peak period is when everyone uses electricity at the same time: in the morning and late in the day. In Québec, these peaks are bigger in winter, since most households heat with electricity. Hydro-Québec says Québec uses almost twice as much electricity in winter as in summer.

During cold snaps, Hydro-Québec can ask customers to cut back at specific times: these are peak events. According to Hydro-Québec:

• they can happen from December 1 to March 31, from 6 to 10 a.m. or from 4 to 8 p.m.;
• there can be up to 30 per winter, two a day at most, and each one lasts four hours;
• there are none on December 24, 25, 26 and 31, January 1 and 2, Good Friday and Easter Monday;
• there's no set temperature threshold: they're called when Hydro-Québec expects high demand, which mostly happens on cold days.

If you're on the Flex D rate, you get a notice the day before by email or through the Hydro-Québec or Hilo app, with the start and end times.

The Flex D rate in a nutshell

With the Flex D rate, Hydro-Québec explains that electricity costs less than the base rate more than 95% of the winter period, but more during peak events. The rest of the year, the base rate applies. Hydro-Québec mentions savings of up to 20% on your winter bill, depending on how much you cut back during peaks.

For winter 2025-2026, Hydro-Québec reports nearly 140,000 households enrolled and estimated average savings of $90 without smart thermostats and $150 with smart thermostats, before taxes. There's a manual option (you adjust things yourself) and an automated option with Hilo. You can opt out at any time by calling Hydro-Québec; some conditions apply to the automated option.

This rate isn't for everyone: it pays off mostly if you can really cut back during peaks. The details and sign-up are in your Hydro-Québec Customer Space.

How to set your heat pump during a peak event

1. Pre-heat before the event

Hydro-Québec suggests pre-heating your home a few hours before the peak event starts so you don't feel uncomfortable during it. With a heat pump, that's the time to let it work: it heats much more efficiently than baseboards. According to Hydro-Québec, it can be up to three times more efficient than electric baseboards.

2. Turn it down at least 2 °C when the peak starts

Hydro-Québec recommends lowering the heat by at least 2 °C at the start of a peak period. When you lower the setpoint, the heating stops for a while: the bigger the drop, the longer it stays off and the more you save. A well pre-heated house holds its heat for quite a while.

3. Start with the baseboards, especially in empty rooms

If you have a wall-mounted heat pump, Hydro-Québec suggests lowering the baseboard setpoints, especially in rooms nobody is using, to stay comfortable where you are. Keep the basic rule in mind: baseboards set about 2 °C lower than the heat pump, so they only kick in when it's very cold. We explain it in How to set your heat pump in winter.

4. Stay in Heat mode

Don't switch to Auto mode for the occasion: Hydro-Québec recommends Heat mode all winter. After the event, go back to your usual settings.

5. Put off the rest

Hydro-Québec also suggests using hot water after high-demand hours, putting off the dryer and dishwasher, and charging your electric vehicle overnight if you can.

What about a heat storage unit?

If your home has central heating, a heat storage unit (an "accumulateur de chaleur") takes it a step further. According to Hydro-Québec, it's an all-electric central heating system, with no fuel, that stores heat in a mass of high-density ceramic bricks. Outside peak hours, electric elements heat up the bricks. The unit is programmed so its elements shut off during peak events, and your home stays warm with the heat stored in the bricks, without you touching the thermostat.

A heat storage unit can also be paired with a central heat pump, whose coil fits right into the unit. Hydro-Québec recommends signing up for the Flex D rate with this system, and says pairing it with a central heat pump can save you even more.

At ClimaRéf, we install heat storage units and we're certified to do it. See our central heat pumps and heat storage page.

A heat pump in good shape means fewer baseboards during peaks

Peak events often fall on the coldest days, when the heat pump works hardest and the baseboards kick in more easily. To get the most out of it:

• Keep the filters clean. Hydro-Québec recommends checking or cleaning them every month. See our article on cleaning filters.
• Keep the outdoor unit clear of loose snow. Never chip at the ice yourself: we explain what to do in My heat pump stops heating when it's cold.
• Have it maintained by a technician before or during the cold season.

If you don't have a heat pump yet, Hydro-Québec recommends an ENERGY STAR Cold Climate certified model for Québec winters.

Sources

• Hydro-Québec, Comprendre les périodes de pointe (in French; peak periods and simple steps).
• Hydro-Québec, Flex D rate (how it works, 2025-2026 results and FAQ).
• Hydro-Québec, Thermopompe murale ou centrale (in French; efficiency, settings and FAQ).
• Hydro-Québec, Chauffage central avec accumulateur de chaleur (in French; how it works).
• Hydro-Québec, Avantages du chauffage central avec accumulateur de chaleur (in French; Flex D pairing).