Heat Pump Lockout Temperature: What to Set on Your Hybrid System in Durham Region
Written by Zack Laundrie | Licensed HVAC Technician, Durham Region | Published on May 7, 2026
If you have a hybrid heat pump system, there is one setting that affects your comfort and your heating bill more than almost anything else: the lockout temperature. It tells your system exactly when to stop using the heat pump and hand off to the furnace. Set it too high and your furnace carries loads the heat pump could handle efficiently at a fraction of the cost. Set it too low and your heat pump is grinding away in conditions where it is barely keeping up, which stresses the equipment and defeats the purpose of the hybrid setup.
Most homeowners in Oshawa, Whitby, Ajax, Pickering, Bowmanville, and Port Perry never touch this setting after installation. Some do not even know it exists. This post explains what it is, how it works, and where to set it for Durham Region winters.
What Is a Heat Pump Lockout Temperature?
A lockout temperature (sometimes called a balance point or changeover temperature) is the outdoor air temperature below which your thermostat or control board switches from heat pump heating to furnace heating. Above that threshold, the heat pump runs. Below it, the furnace takes over.
On a properly configured hybrid system, the two pieces of equipment should rarely run at the same time. The lockout setting is what keeps them from fighting each other. Without a clear handoff point, both systems can cycle on and off unpredictably, which wastes energy, causes temperature swings, and adds unnecessary wear to both units.
The lockout temperature is usually set one of two ways: through the thermostat or through the heat pump control board itself. Some installers configure it during commissioning and never explain it to the homeowner. Others leave it at a factory default that was not designed for Ontario winters.
What Happens When It Is Set Wrong
Too high (10°C or above) and your furnace kicks in on mild fall and spring days when the heat pump is at its most efficient. You are burning gas when you could be moving heat at a coefficient of performance of 3 or 4. That is money going out the flue.
Too low (say, -20°C) and your heat pump is running on the coldest nights of the year, when its output has dropped significantly and your furnace could heat the home faster and more reliably. The heat pump is working hard for diminishing returns while your indoor temperature drifts down.
The right setting sits in the middle, and it depends on your specific equipment and your home.
What Lockout Temperature Makes Sense for Durham Region?
Durham Region winters are cold but not extreme by Ontario standards. Oshawa and Whitby typically see design temperatures around -18°C to -20°C on the coldest nights, with most of the heating season landing in the -5°C to -15°C range. That is actually good news for heat pump efficiency: modern cold-climate units from Mitsubishi and similar manufacturers maintain strong output well into the negative teens.
For most hybrid systems in Durham Region using a quality cold-climate heat pump, a lockout temperature between -10°C and -15°C is a reasonable starting point. This lets the heat pump handle the vast majority of heating hours through fall, winter, and spring, while the furnace steps in only when temperatures drop to the range where the heat pump’s efficiency advantage shrinks.
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Why This Range — and Not Something Fixed
Every home and every system is different. The right lockout temperature depends on the heat pump model and its rated output at various temperatures, the size and insulation level of the home, the heating load calculation done at the time of installation, and how the thermostat or control board handles the transition.
A Mitsubishi Hyper Heat unit, for example, is rated to produce meaningful output down to -25°C. Setting its lockout at -10°C leaves a lot of efficient heating capacity on the table. But a less capable unit installed in a poorly insulated older home in Bowmanville might genuinely struggle below -12°C, making a higher lockout the right call.
This is one of the reasons a proper heat loss calculation matters at the time of installation. If the sizing was done right, your installer should be able to tell you exactly where your home’s balance point sits and set the lockout accordingly.
What About the Factory Default?
Most heat pumps ship with a factory default lockout somewhere around 0°C or slightly below. In a Durham Region winter, that means your furnace kicks in almost every night from November through March. The heat pump barely runs in heating mode at all, and most of the efficiency advantage of the hybrid system is lost.
If your hybrid system was installed and the lockout was never adjusted from the factory setting, there is a good chance you are running your furnace far more than you need to.
How to Check and Adjust Your Lockout Temperature
Where you find this setting depends on your setup. On a smart thermostat like an Ecobee, it is usually buried in the equipment settings under a label like “Compressor Min Outdoor Temp” or “Heat Pump Min Temp.” On a Honeywell T6 or similar, it may be in the installer configuration menu. Some systems handle lockout through a sensor connected directly to the heat pump control board rather than the thermostat.
If you are not sure where your lockout is set, or whether it was set at all, the fastest approach is to check your commissioning report if your installer provided one. HVAC Zack leaves every customer a documented commissioning report with airflow, static pressure, and control settings at the time of installation, so this should not be a mystery.
If your hybrid system was installed and the lockout was never adjusted from the factory setting, there is a good chance you are running your furnace far more than you need to.
Adjusting It Yourself vs. Calling a Tech
Changing a thermostat-based lockout setting is something a confident homeowner can do. The menus are accessible, and the change is reversible. If you are using an Ecobee or similar smart thermostat, the manufacturer’s app or web portal usually makes this straightforward.
Adjusting a control board-level lockout is a different story. That typically requires accessing the outdoor unit, connecting to the board, and understanding how your specific equipment handles the transition. Getting it wrong can result in the furnace and heat pump running simultaneously, which adds wear and can cause control conflicts. That work is better left to a licensed technician.
If you are in Oshawa, Whitby, Ajax, Pickering, Port Perry, or Bowmanville and you want someone to verify your lockout setting and confirm your hybrid system is configured properly, that is exactly the kind of heat pump service call HVAC Zack handles regularly.
Lockout Temperature vs. Balance Point: Are They the Same Thing?
You will sometimes hear these terms used interchangeably, but they refer to slightly different concepts.
The balance point is the outdoor temperature at which your home’s heat loss equals the heat pump’s output. Below the balance point, the heat pump cannot keep up on its own and supplemental heat is needed. This is a property of your home and your equipment together, and it is calculated, not chosen.
The lockout temperature is the setting that tells the system when to actually switch. Ideally, you set it at or near the balance point so the transition happens exactly when it makes physical sense. But in practice, many installers set it slightly above the balance point to give the furnace a bit of runway before temperatures drop to the point where the heat pump is genuinely struggling.
In Durham Region, with design temperatures around -18°C to -20°C and a cold-climate heat pump, the balance point for a typical well-insulated home often sits somewhere between -12°C and -18°C depending on the unit. That is why a lockout in the -10°C to -15°C range lands in the right neighbourhood for most installations here.
What If Your System Feels Off Regardless of the Setting?
Lockout temperature is one piece of the puzzle, but it is not the only thing that affects hybrid system performance. If your home is not staying comfortable, or if your furnace seems to be running constantly even in mild weather, the lockout may not be the culprit.
Other things worth checking include whether your heat pump is properly sized for the home, which is addressed in detail in this guide to heat pump sizing for Ontario homes. Ductwork condition matters too — restricted airflow will limit what any heat pump can deliver regardless of how the controls are configured. If you have noticed issues since installation, it is also worth confirming that the original installation was done correctly, including commissioning and refrigerant charge.
Homeowners in Ajax, Pickering, Whitby, Oshawa, Bowmanville, and Port Perry who have had heat pump issues over the past winter, whether noise, inconsistent heat, or higher-than-expected bills, may be dealing with something deeper than a lockout setting. A diagnostic visit covers all of this.
It is also worth reading about common heat pump repair issues in Durham Region if you are trying to figure out whether a service call makes sense before the cooling season starts.
Getting It Right the First Time
The lockout temperature conversation is one HVAC Zack has with every hybrid system customer in Durham Region. It is part of the commissioning process on every heat pump installation, and it gets documented so the homeowner knows exactly what was set and why.
If you have a hybrid system that was installed by someone else, or if you are not sure whether your lockout was ever configured properly, a one-hour service visit is enough to check the setting, verify the system is transitioning correctly, and make adjustments if needed. That is true whether you are in Oshawa, Whitby, Ajax, Pickering, Port Perry, or Bowmanville.
For homeowners still deciding whether a hybrid system makes sense at all, the post on why hybrid heat pump systems work well for Durham Region winters is a good place to start.
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About The Author
Zack Laundrie is a licensed and insured HVAC technician with over 15 years of hands-on experience serving Durham Region homeowners. He specializes in heat pump installation, hybrid systems, and honest diagnostics across Oshawa, Whitby, Ajax, Pickering, Bowmanville, and Port Perry.