A System-By-System Look At Night And Away Setbacks
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You have been told, correctly, that turning the thermostat down at night saves money. You may have been told a version of it by a utility, by a government website, by the person who installed your furnace, and by your father. It is one of the most repeated pieces of household advice in Canada, and for most of the twentieth century it was simply true.
Then the heating system under it changed. A gas furnace produces very hot air on demand and recovers a cold house quickly, so a deep overnight setback costs nothing to reverse. A heat pump does not work that way. Neither does a concrete slab with tubing in it, or a boiler feeding cast-iron radiators through an outdoor reset control. On those systems, the morning recovery is not free — and on the most common configuration in new Canadian installations, an air-source heat pump with electric backup, the recovery can be paid for at roughly three times the price of the heat you saved overnight.
This is not a case of the standard advice being wrong. It is a case of the standard advice having a stated exception that almost nobody reads, and that exception now covering a large and growing share of Canadian homes. The reader who set their thermostat to drop to 16°C at 11 p.m. and climb back to 21°C at 6 a.m. did not make an error of judgment. They applied furnace logic to equipment that is not a furnace.
What follows is a catalogue: the setback mistake specific to each type of heating system, what physically happens when you make it, what the recovery costs you, and what to do instead. There is a table partway down that condenses all of it into one view, and a short list of thermostat settings worth checking before the first cold snap. Some readers will finish this and set back more aggressively than they do now. Others will stop setting back almost entirely. Which of those you are depends entirely on what is in your basement or bolted to the side of your house.
The physics behind the old rule are sound and worth stating plainly. A house loses heat in proportion to the difference between inside and outside temperature. Let the inside temperature fall and the gap narrows, so the house leaks less heat for those hours. The energy you save is real, and it is not returned in full when you reheat, because the house spent the night losing less than it otherwise would have.
Canada puts a number on it. According to Natural Resources Canada, a drop of 1°C over an eight-hour period saves roughly 2 percent of heating energy, and turning the temperature down is worthwhile any time you are away for more than three or four hours. That is the foundation the entire genre of energy-saving tips rests on.
The myth that the reheat cancels the saving has been addressed directly by Canadian utilities. Hydro-Québec states that turning the heating back on never uses more electricity than was saved while the system was off, because the system uses the electricity it needs and no more. For electric resistance heating, that is exactly right. Resistance heat converts electricity to heat at the same rate whether it is holding a temperature or climbing to one, so the recovery is simply the saved energy being spent back, minus the losses you avoided.
Hold onto that sentence, because it contains the hidden condition. The classic rule is true when recovery costs the same per unit of heat as steady operation. Every system in this article that breaks the rule breaks it at precisely that point.
And the federal guidance says so, in a subordinate clause that no consumer article repeats. Natural Resources Canada's own wording is that "except for some hydronic systems and heat pumps with slow response times, you can save energy by turning down your thermostat." The exception was always there. It was just never the headline.
Before getting into systems, there is a habit worth killing that applies to all of them: setting the thermostat higher than you want in order to get there faster.
BC Hydro is blunt about it — rooms do not heat up any faster when you set 24°C instead of 21°C. A thermostat is a switch, not a throttle. Most heating equipment has one output, or two, and it runs flat out until the setpoint is reached regardless of how far above the target you set the dial. Setting 24°C does not accelerate anything. It just guarantees the system keeps running past the point where you were comfortable.
On a furnace, that costs you extra runtime. On a heat pump, it costs considerably more, for reasons the next section explains.
The physics behind the old rule are sound and worth stating plainly. A house loses heat in proportion to the difference between inside and outside temperature. Let the inside temperature fall and the gap narrows, so the house leaks less heat for those hours. The energy you save is real, and it is not returned in full when you reheat, because the house spent the night losing less than it otherwise would have.
Canada puts a number on it. According to Natural Resources Canada, a drop of 1°C over an eight-hour period saves roughly 2 percent of heating energy, and turning the temperature down is worthwhile any time you are away for more than three or four hours. That is the foundation the entire genre of energy-saving tips rests on.
The myth that the reheat cancels the saving has been addressed directly by Canadian utilities. Hydro-Québec states that turning the heating back on never uses more electricity than was saved while the system was off, because the system uses the electricity it needs and no more. For electric resistance heating, that is exactly right. Resistance heat converts electricity to heat at the same rate whether it is holding a temperature or climbing to one, so the recovery is simply the saved energy being spent back, minus the losses you avoided.
Hold onto that sentence, because it contains the hidden condition. The classic rule is true when recovery costs the same per unit of heat as steady operation. Every system in this article that breaks the rule breaks it at precisely that point.
And the federal guidance says so, in a subordinate clause that no consumer article repeats. Natural Resources Canada's own wording is that "except for some hydronic systems and heat pumps with slow response times, you can save energy by turning down your thermostat." The exception was always there. It was just never the headline.
Before getting into systems, there is a habit worth killing that applies to all of them: setting the thermostat higher than you want in order to get there faster.
BC Hydro is blunt about it — rooms do not heat up any faster when you set 24°C instead of 21°C. A thermostat is a switch, not a throttle. Most heating equipment has one output, or two, and it runs flat out until the setpoint is reached regardless of how far above the target you set the dial. Setting 24°C does not accelerate anything. It just guarantees the system keeps running past the point where you were comfortable.
On a furnace, that costs you extra runtime. On a heat pump, it costs considerably more, for reasons the next section explains.
If you heat with a gas or oil furnace and forced air, the traditional advice applies to you more or less as written. Set back overnight. Set back when the house is empty. The recovery is fast because the equipment delivers air at a temperature far above room temperature, and the only cost of recovery is a longer burner cycle.
A few refinements are still worth making.
One caution specific to older houses on a single thermostat: the room with the thermostat recovers first and the bedrooms at the end of the duct run recover last. If you have been setting back deeply and waking up to a cold back bedroom, the problem is distribution, not the setback schedule.
The winter ahead is being forecast in two very different ways, which is worth a look before you commit to a season's worth of schedule.
This is the configuration where the traditional advice does the most damage, and it is now extremely common in Canadian homes.
The mechanism is a staging decision made by the thermostat, not a fault in the equipment. Most ducted single-speed systems are wired to a two-stage heat thermostat: stage one calls the heat pump, and, as Natural Resources Canada describes it, stage two calls the supplementary heating system if the indoor temperature continues to fall below the desired temperature. That supplementary system is usually a bank of electric resistance strips.
Now run the morning. At 6 a.m. the setpoint jumps from 16°C to 21°C. The thermostat sees a five-degree gap. The compressor starts, and on a cold morning it is producing heat at a fraction of the capacity it manages in milder weather. The indoor temperature climbs slowly. The gap does not close fast enough, so stage two engages, and the strips do the rest of the work.
The federal guidance describes the result without flinching: the heat pump may not be able to supply all the heat needed on short notice, the supplementary system runs until the heat pump catches up, and this reduces the savings you expected. Put in cost terms, you spent the night banking heat at the compressor's efficiency and bought it back in the morning at resistance-heat efficiency. The compressor's advantage over resistance heat narrows as it gets colder, but it does not disappear — which is exactly why handing the recovery to the strips is such a poor trade.
So what is the correct setback? Canada has an unusually clear answer, and it comes with a number attached: moderated setbacks of not more than 2°C, or a smart thermostat that starts the system early in anticipation of the recovery.
Efficiency Nova Scotia arrives at the same band from a different direction, telling homeowners to lower the temperature by 1 to 2°C at night or when away, and to avoid deep setbacks like dropping to 15°C, which may engage resistance heating and cancel out any savings. It also names the underlying habit rather than the setting: keep your settings steady, because frequent changes trigger auxiliary heat.
Three Canadian authorities, in three provinces, giving the same instruction is rare enough on any homeowner question that it is worth treating as settled.
This is the configuration where the traditional advice does the most damage, and it is now extremely common in Canadian homes.
The mechanism is a staging decision made by the thermostat, not a fault in the equipment. Most ducted single-speed systems are wired to a two-stage heat thermostat: stage one calls the heat pump, and, as Natural Resources Canada describes it, stage two calls the supplementary heating system if the indoor temperature continues to fall below the desired temperature. That supplementary system is usually a bank of electric resistance strips.
Now run the morning. At 6 a.m. the setpoint jumps from 16°C to 21°C. The thermostat sees a five-degree gap. The compressor starts, and on a cold morning it is producing heat at a fraction of the capacity it manages in milder weather. The indoor temperature climbs slowly. The gap does not close fast enough, so stage two engages, and the strips do the rest of the work.
The federal guidance describes the result without flinching: the heat pump may not be able to supply all the heat needed on short notice, the supplementary system runs until the heat pump catches up, and this reduces the savings you expected. Put in cost terms, you spent the night banking heat at the compressor's efficiency and bought it back in the morning at resistance-heat efficiency. The compressor's advantage over resistance heat narrows as it gets colder, but it does not disappear — which is exactly why handing the recovery to the strips is such a poor trade.
So what is the correct setback? Canada has an unusually clear answer, and it comes with a number attached: moderated setbacks of not more than 2°C, or a smart thermostat that starts the system early in anticipation of the recovery.
Efficiency Nova Scotia arrives at the same band from a different direction, telling homeowners to lower the temperature by 1 to 2°C at night or when away, and to avoid deep setbacks like dropping to 15°C, which may engage resistance heating and cancel out any savings. It also names the underlying habit rather than the setting: keep your settings steady, because frequent changes trigger auxiliary heat.
Three Canadian authorities, in three provinces, giving the same instruction is rare enough on any homeowner question that it is worth treating as settled.
If your heat pump is ductless — a wall-mounted head with a remote — there is usually no electric backup wired to it at all, and the failure mode is different. A deep setback there will not trigger resistance strips, but it may leave a cold-soaked house that the unit cannot recover before you need it, especially in shoulder rooms the head does not reach.
There is more to how a heat pump behaves in a Canadian winter than the thermostat schedule, including capacity, noise and ice, and it is worth understanding before you judge the equipment.
A homeowner watching the morning recovery sees "AUX" appear on the thermostat, assumes something is broken, and switches the system to Emergency Heat. This is one of the most expensive three-second decisions available in a Canadian winter, and it is entirely a labelling problem.
Auxiliary heat runs alongside the heat pump. It is a supplement, it is designed to behave this way, and seeing it during a cold snap is normal. Emergency heat is different: it locks the heat pump out entirely and runs the backup alone. Resideo documents the behaviour plainly — in emergency heat mode the heat pump is locked out and the backup heat is used to maintain the setpoint.
A homeowner who flips that switch in November and forgets about it has turned off the efficient half of their heating system for the winter and will heat the entire season on resistance strips or a furnace. The setting exists for one situation, described precisely by BC Wide Heating: emergency heat is for when the outdoor unit is genuinely out of service.
The practical rule: Aux appearing during a cold snap is the system working. Aux appearing on a mild afternoon, or running for hours after the house has reached temperature, is a settings problem.
Some of what looks like a fault in winter is a defrost cycle doing its job, which is worth ruling out before you touch anything.
Here is the part almost no homeowner has seen. The decision to run resistance heat is governed by named, adjustable settings, and the factory values were not chosen for a Canadian winter.
ecobee publishes the full list, and four entries matter here: Compressor Min Outdoor Temperature sets the lowest outdoor temperature at which the compressor will operate; Aux Heat Max Outdoor Temperature prevents auxiliary heat from running above a given outdoor temperature; Compressor to Aux Temperature Delta sets the indoor gap that triggers auxiliary heat; and Aux Reverse Staging drops the auxiliary heat near the end of a cycle so the heat pump finishes the job. Note that these can only be changed on the thermostat itself, not in the phone app.
The first of those settings deserves particular attention. The documented factory default for Compressor Min Outdoor Temperature is 35°F — about 1.7°C — and below that threshold the thermostat stops using the compressor and relies on auxiliary heat to warm the home. Read that again in Canadian terms. A default left untouched would hand most of the heating season, in most of this country, to electric resistance strips, on equipment that may be rated to run efficiently at −25°C.
That is not a claim that every thermostat ships this way or that yours is set wrong. It is a claim that this is a setting with a real default, that the default is climate-inappropriate for Canada, and that nobody is going to check it for you.
The other feature worth confirming is adaptive recovery, which is what makes a deeper setback survivable. Resideo's documentation describes it as calculating a recovery ramp from how far the room is from setpoint, previous equipment performance, and weather history — and, critically, on a heat pump with electric auxiliary it runs two ramps, compressor first, with auxiliary engaging if the temperature rise is not enough. So adaptive recovery reduces the odds of calling the strips. It does not eliminate them, and it can be switched off.
If you want to know whether yours is working, Honeywell Home notes that a thermostat in this mode displays the words "Active Recovery" beneath the room temperature while climbing from a setback. If you have never seen that message during a morning warm-up, the feature is likely off or unsupported.
Here is the part almost no homeowner has seen. The decision to run resistance heat is governed by named, adjustable settings, and the factory values were not chosen for a Canadian winter.
ecobee publishes the full list, and four entries matter here: Compressor Min Outdoor Temperature sets the lowest outdoor temperature at which the compressor will operate; Aux Heat Max Outdoor Temperature prevents auxiliary heat from running above a given outdoor temperature; Compressor to Aux Temperature Delta sets the indoor gap that triggers auxiliary heat; and Aux Reverse Staging drops the auxiliary heat near the end of a cycle so the heat pump finishes the job. Note that these can only be changed on the thermostat itself, not in the phone app.
The first of those settings deserves particular attention. The documented factory default for Compressor Min Outdoor Temperature is 35°F — about 1.7°C — and below that threshold the thermostat stops using the compressor and relies on auxiliary heat to warm the home. Read that again in Canadian terms. A default left untouched would hand most of the heating season, in most of this country, to electric resistance strips, on equipment that may be rated to run efficiently at −25°C.
That is not a claim that every thermostat ships this way or that yours is set wrong. It is a claim that this is a setting with a real default, that the default is climate-inappropriate for Canada, and that nobody is going to check it for you.
The other feature worth confirming is adaptive recovery, which is what makes a deeper setback survivable. Resideo's documentation describes it as calculating a recovery ramp from how far the room is from setpoint, previous equipment performance, and weather history — and, critically, on a heat pump with electric auxiliary it runs two ramps, compressor first, with auxiliary engaging if the temperature rise is not enough. So adaptive recovery reduces the odds of calling the strips. It does not eliminate them, and it can be switched off.
If you want to know whether yours is working, Honeywell Home notes that a thermostat in this mode displays the words "Active Recovery" beneath the room temperature while climbing from a setback. If you have never seen that message during a morning warm-up, the feature is likely off or unsupported.
Give yourself ten minutes with the thermostat before the first hard freeze, not during it. Menus differ by brand, the settings are usually two or three levels deep under installer or threshold options, and some manufacturers recommend calling support before changing thresholds if you are not certain what your equipment can do.
A dual-fuel system pairs a heat pump with a gas or oil furnace instead of electric strips. The setback mistake is the same in shape but different in consequence: instead of buying your morning recovery at resistance-heat prices, you buy it in fuel, and the furnace happily takes the job any time the thermostat asks.
The concept that governs the whole system is the balance point — the outdoor temperature at which the home's heat loss equals what the heat pump can deliver. Above it, the heat pump can carry the house alone and any furnace runtime is pure waste. Below it, the furnace is genuinely needed.
U.S. Department of Energy research on heat pump commissioning states the requirement directly: for dual-fuel or backup-heat systems, it is important to ensure the backup heat source only operates below the balance point temperature. That is a commissioning item, meaning it was either set correctly when your system was installed or it was not — and it is checkable after the fact.
The trade puts a band on it too. Northeast Energy Efficiency Partnerships advises installers to fit an outdoor cutout control so the central backup heat is locked out above a cutout temperature, set somewhere between 20 and 35°F — roughly −7°C to +2°C — and adjusted for occupant comfort.
Worth noting: that same installer guide contains no homeowner guidance on setback at all. The operating question this article answers is not covered by the trade's own cold-climate installation guide, which is a reasonable explanation for why so few installers raise it at handover.
So the dual-fuel question to ask is not "how deep should I set back?" It is "at what outdoor temperature is my furnace allowed to run at all?" Get that answer and the setback question mostly resolves itself.
If your house is heated by electric baseboards, everything above about restraint does not apply to you. Set back, set back deeply, and set back room by room.
Baseboards have the three properties that make setback ideal. They respond in minutes rather than hours. They have no second stage to trip, because resistance heat is already the most expensive heat in the house and there is nothing more expensive for the thermostat to escalate to. And they are zoned by default — every room has its own thermostat, which means a spare bedroom, a basement office and a laundry room can each hold a different schedule.
That last point is the one most baseboard owners leave on the table. The question is not "what temperature should the house be overnight?" but "which of these eleven rooms needs to be warm at 3 a.m.?" Heating unoccupied rooms is the largest avoidable waste in a baseboard house, and the fix is a schedule per room, not a schedule per house.
The controls have quietly improved, too. Canada's minimum performance standard for line-voltage thermostats, based on CSA C828-19, requires droop of no more than 1.5°C and a differential of 0.50°C on wall-mounted and two-component types, applying to units manufactured on or after July 1, 2026, with built-in types following a year later. A thermostat holding a room within half a degree behaves nothing like the old bimetallic dial that swung three degrees either side of the mark — which is why a room-by-room setback strategy that would have been miserable twenty years ago is comfortable now.
If you are still running round dial thermostats, that is the upgrade that makes the rest of this section work.
Water-based heating is where setback goes from inefficient to counterproductive, and where the federal carve-out quoted at the top of this article lands.
A heated concrete slab is a battery. Its entire design virtue is that it stores heat and releases it slowly and evenly, which is also precisely why it cannot be scheduled like a furnace. Telling a slab to be four degrees cooler at midnight and four degrees warmer at six is asking a thousand kilograms of concrete to change its mind twice in a working day.
The counterintuitive part is that better houses are worse candidates. U.S. Department of Energy Building America research measured recovery time against building heat capacity in hydronic homes and found a super-insulated house took 6.9 hours to recover from a setback, a house built to a 2009 code took 3.4 hours, and an old uninsulated house took 1.0 hour. Tighter, heavier, better-built homes recover slowest, because the same mass that keeps them comfortable resists being told what to do.
Run that against a normal schedule. A 6.9-hour recovery started at 5 a.m. delivers comfort in the early afternoon. The house is not saving energy overnight in any useful sense — it is spending the morning climbing back, often overshooting in the afternoon as the slab keeps discharging heat it absorbed hours earlier.
The correct practice for a slab is a flat setpoint with outdoor reset doing the modulation, and if you must vary it, by no more than a degree, with the change commanded hours before you want the effect.
A boiler feeding radiators has a similar problem with an additional control conflict layered on top.
Outdoor reset is the feature that makes a modern condensing boiler efficient: as the weather gets milder, it lowers the water temperature it sends to the radiators. But a setback recovery demands extra output at exactly the moment outdoor reset is holding water temperature down. The two controls are working against each other.
The same Building America research documents where that leads, noting that with outdoor reset in use the home may never recover from setback, and that special controls to bypass the outdoor reset sensor are needed in that case. It also lists homes with non-modulating boilers, super-insulated homes, radiant systems and uninsulated concrete construction as poor candidates for setback generally.
If your radiator house has felt like it never quite warms up in the morning no matter how early the schedule starts, this is very likely the reason, and it is a controls conversation with your heating contractor rather than a scheduling one.
Water-based heating is where setback goes from inefficient to counterproductive, and where the federal carve-out quoted at the top of this article lands.
A heated concrete slab is a battery. Its entire design virtue is that it stores heat and releases it slowly and evenly, which is also precisely why it cannot be scheduled like a furnace. Telling a slab to be four degrees cooler at midnight and four degrees warmer at six is asking a thousand kilograms of concrete to change its mind twice in a working day.
The counterintuitive part is that better houses are worse candidates. U.S. Department of Energy Building America research measured recovery time against building heat capacity in hydronic homes and found a super-insulated house took 6.9 hours to recover from a setback, a house built to a 2009 code took 3.4 hours, and an old uninsulated house took 1.0 hour. Tighter, heavier, better-built homes recover slowest, because the same mass that keeps them comfortable resists being told what to do.
Run that against a normal schedule. A 6.9-hour recovery started at 5 a.m. delivers comfort in the early afternoon. The house is not saving energy overnight in any useful sense — it is spending the morning climbing back, often overshooting in the afternoon as the slab keeps discharging heat it absorbed hours earlier.
The correct practice for a slab is a flat setpoint with outdoor reset doing the modulation, and if you must vary it, by no more than a degree, with the change commanded hours before you want the effect.
A boiler feeding radiators has a similar problem with an additional control conflict layered on top.
Outdoor reset is the feature that makes a modern condensing boiler efficient: as the weather gets milder, it lowers the water temperature it sends to the radiators. But a setback recovery demands extra output at exactly the moment outdoor reset is holding water temperature down. The two controls are working against each other.
The same Building America research documents where that leads, noting that with outdoor reset in use the home may never recover from setback, and that special controls to bypass the outdoor reset sensor are needed in that case. It also lists homes with non-modulating boilers, super-insulated homes, radiant systems and uninsulated concrete construction as poor candidates for setback generally.
If your radiator house has felt like it never quite warms up in the morning no matter how early the schedule starts, this is very likely the reason, and it is a controls conversation with your heating contractor rather than a scheduling one.
This is the article in one view. Find your system, read across.
Print it, screenshot it, or keep it open while you rebuild your schedule. The row you need is the row that matches the equipment you actually own, which is not always the equipment you think you own — a "heat pump" quote that included a new furnace is a dual-fuel system, and a house with radiators in some rooms and a slab in the basement is two rows at once.
Everything above concerns efficiency. The floor on a setback is set by two other things entirely, and both of them matter more than the money.
The first is your building envelope. Natural Resources Canada advises against reducing the temperature below 17°C because of the risk of moisture building up in the exterior walls. That is a durability limit, not a comfort preference, and it applies to occupied homes on a normal schedule. It is the reason a 15°C overnight setback is a poor idea even in a house where nothing would freeze.
The second is your insurance policy, and this is where a vacation setback stops being an energy decision. The Insurance Bureau of Canada states that standard policies cover damage from freezing and burst pipes provided the pipes are in the heated portion of the home and reasonable steps are taken to maintain heat, and that most policies set out how often the home must be checked by a competent person to confirm heat is being maintained. A deep setback before a two-week absence can put you on the wrong side of a condition you have never read.
What does that look like in numbers? Square One Insurance is one of the few Canadian insurers to publish a threshold, telling its own customers that absences of seven days or less during heating season require no extra steps, while beyond seven days they must either maintain heat with periodic checks or shut off the water and drain the pipes, hot water tank included. That is Square One's wording for Square One's policies — your insurer's number may be different, and the only way to know is to read your own wording.
One piece of context that trips people up: the 21°C figure lodged in Canadian heads is a tenancy standard, not a homeowner rule. The City of Toronto requires a minimum of 21°C between October 1 and May 15 where heating is provided at the property owner's expense — that is, in rental units. Nothing obliges an owner-occupier to hold 21°C, and knowing where the number came from frees you to choose your own.
If you are leaving a home or cottage unheated or deeply set back for an extended period, the failure mode is not a high bill. It is a burst pipe in an empty house, discovered days later. Shutting off the water and draining the system is the genuinely safe option, and in many policies it is the alternative your insurer explicitly offers.
There is an honest limit to what a schedule can fix, and a reader whose backup heat runs constantly even on a flat setpoint should know where that limit is.
Natural Resources Canada notes that an undersized heat pump means the supplementary heating system gets used more frequently, full stop. No setback strategy corrects an equipment capacity shortfall. If your aux indicator is on for hours at −5°C with a flat schedule and clean filters, you are looking at a sizing or commissioning problem, not a scheduling one.
Canadian systems are meant to be sized against a specific national standard — the residential load-calculation standard published by CSA Group, which was reaffirmed in 2025 and remains current. It is reasonable to ask an installer whether a calculation to that standard was performed for your home and to see the output.
The other candidates worth ruling out before blaming the schedule: a dirty filter restricting airflow, a compressor lockout set too high, an aux lockout not set at all, and a system still running in emergency heat from a cold snap two winters ago.
Sizing is the decision underneath most of these symptoms, and it is worth understanding even after installation.
Short version, by system.
The thread running through all of it is that the thermostat schedule is not a universal best practice you can copy from a tips page. It is a setting that has to match the physics of the equipment behind it. Get the match right and the savings take care of themselves.
About the Author
Ryan is the founder of Homeowner.ca and a proud Canadian homeowner based in Guelph, Ontario. Over his 25-year career in digital publishing, he has focused on transforming complex information into clear, practical guidance that helps people make confident, well-informed decisions.
On a gas or oil furnace and on electric baseboards, yes. Natural Resources Canada puts the figure at about 2 percent of heating energy for every 1°C of setback over an eight-hour period. On a heat pump, a slab or a boiler with outdoor reset, the answer depends on how deep the setback is and how the system recovers — which is what this article is about.
No more than 2°C is the guidance from Natural Resources Canada, and Efficiency Nova Scotia recommends the same 1 to 2°C band while explicitly warning against dropping to 15°C. A deeper setback is only defensible if you have confirmed that adaptive recovery is enabled and that your auxiliary heat lockouts are set appropriately.
It means auxiliary heat is running alongside the heat pump, usually electric resistance strips. On a very cold day, that is normal and expected. On a mild day, or for hours after the house has reached temperature, it points to a settings problem — most often a compressor lockout set too high or an aux lockout not set at all.
No. Emergency heat locks out the heat pump entirely and runs the backup alone, which is the most expensive way to heat the house. It exists for one situation: the outdoor unit is out of service. If you switched to it during a cold snap and forgot, you may have heated the rest of the season on backup heat.
Because that lag is the design, not a fault. A heated slab stores heat and releases it slowly, which is what makes it comfortable. Building America research measured recovery from a setback at up to 6.9 hours in a well-insulated home — and better-built homes recover more slowly, not faster, because the same thermal mass that holds comfort resists change.
If the boiler has outdoor reset, the reset control is lowering water temperature at exactly the moment the recovery needs it raised. U.S. Department of Energy research found that in this configuration a home may never recover from a setback without special controls to bypass the reset sensor. It is a controls question for your heating contractor.
For an occupied home on a normal schedule, Natural Resources Canada advises against going below 17°C, because of the risk of moisture building up in exterior walls. For an unoccupied home, the limit is set by your insurance conditions and by freeze protection, not by efficiency — and draining the system is often the safer choice over the thermostat.
No. The 21°C figure most Canadians know comes from municipal tenancy standards — in Toronto it applies between October 1 and May 15 where the property owner pays for heat. It binds landlords, not owner-occupiers, and it is not a health threshold.
Partly. Adaptive recovery starts the system early so the compressor has time to close the gap before auxiliary heat is called, and that genuinely buys back some setback depth. But it is a feature that can be switched off, it still calls auxiliary heat when its compressor ramp falls short, and it does nothing about a compressor lockout left at a factory default that is wrong for a Canadian winter.
No. BC Hydro's position is unambiguous: rooms do not heat up faster at 24°C than at 21°C. A thermostat is a switch, not an accelerator. All overshooting does is keep the equipment running past the point where you were comfortable — and on a heat pump, it widens the setpoint gap that triggers backup heat.
