A Heat Pump Primer

View the recording of our great webinar on residential heat pumps.

What is an air source heat pump?

Think of an air conditioner that can run backwards in winter, drawing heat into your home instead of expelling heat as in summer. It surprises most non-physicists that heat can be drawn from (very) cold air, but that is exactly what heat pumps do. About 85% of the heat energy found in air at 21 degrees C is still present at -18 degrees C, which is why heat pumps can produce heat even at very cold temperatures. Because air source heat pumps are reversible, they extract heat from the outside to heat your home in winter and extract heat from inside your home to cool it in summer.



What is the coldest outside temperature where a heat pump can still keep my home warm?

Heat pumps designed specifically for cold-weather climates can meet all of a home’s heating needs, even at the lowest outdoor temperatures. Built-in electric resistance backup heaters kick in when the heat pump struggles to extract heat from super cold outdoor air. The temperature at which this occurs varies depending on the design but is often in the -20 to -30 degree Celsius range.

An important element to ensuring a heat pump will serve your needs is proper sizing. If it is too small, it won’t keep the home warm under really cold conditions. If it is too large, it will run too often during mild weather, causing excessive wear on components. It is a really good idea to insulate and air seal your home as much as possible to keep heat in before installing a heat pump. That’s true no matter what kind of heating system you use, but even more important with a heat pump.


Is this new technology?

No, heat pumps have been in use for over a century. Just like cars though, they have been getting better and better: even a two-decade old heat pump is no match for a modern cold climate heat pump. Heat pumps are commonly used in Scandinavia and Germany among other countries. Sweden had 650,000 units installed as of 2020 and Germany 410,000. According to the International Energy Agency, 180 million heat pumps were in use for heating worldwide in 2020, 1.8 million of which were sold to EU households in 2020 alone. The technology is growing quickly in popularity in Canada, especially for homes that rely on electric heating (see our report on the huge cost savings available from switching from gas to heat pump systems and the equally big savings that heat pumps can generate for electrically heated homes). However, the ability of heat pumps to deliver heat at low outside temperatures has improved significantly in the last decade.


How is this different from ground source/geoexchange type systems?

While systems that exchange heat with the ground are also useful low carbon alternatives to burning gas, they require pipes to be laid underground to circulate the fluids that allow for the exchange of heat. These pipes can be laid horizontally several feet below the surface or drilled vertically deep into the ground. Installing these pipes increases the upfront costs, but because the ground temperature is steady year-round, the increased efficiency of ground source heat pumps can yield significant operational savings. See our report on the even larger savings available for those who have room to accommodate a ground source system.


Should I install a cold weather heat pump or a hybrid system?

If you are replacing your current gas furnace and AC (and don’t wait for that mid-winter breakdown if your system is getting on in years), it can make good sense to opt for a cold weather heat pump that can meet all your heating and cooling needs without needing to maintain a gas furnace as well. With zero interest financing now available through the federal Greener Homes program and some municipalities, the average homeowner will pay less each month in loan and utility payments than they are currently paying for gas and electricity used for heating and cooling thanks to the much greater efficiency of heat pumps.

However, if your furnace is relatively new and you cannot take on more borrowing, a lower upfront cost hybrid system can also lower your energy bills, especially if you opt for a system with a lower design temperature (the temperature at which the gas furnace is needed). These systems can still dramatically reduce the gas you use for heating (by 50-75%) but will require you to maintain two systems: the heat pump and the gas furnace. Some reduced incentives are available for hybrid systems through the Greener Homes program but check the performance criteria carefully.


How expensive is an air source heat pump to operate?

That will depend on the cost of electricity in your area. It’s important to remember that the economics of heating your home with gas will quickly change as Canada’s carbon levy rises from $50 to $170 tonne in the next decade. As well, if you cut your home off from gas completely, you can increase your savings because you are no longer paying a gas service charge every month.

See our reports on the cost advantages of heat pumps for homes with gas equipment and for electrically heated homes.

You can also use our calculator to see how much you could save by switching to a heat pump.


Can you use them in homes with radiators (hydronic systems)?

There are two ways to go if you rely on radiators to heat your home. The first is to install sub-units in each room that are fed by the central heat pump. This style of installation is called a “split” or “minisplit.” The room units look a bit like horizontal space heaters or flat AC units and can be installed at the top or bottom of walls. The benefit of this system is that it can also be used for air conditioning in summer.

Air to water heat pump systems are a simpler option that will use your existing radiators. These systems can be paired with a water storage tank that can also allow you to store heat or cold during off-peak electricity periods. For AC, however, you will need to either replace conventional rads with in-room fan coil units or have in-floor radiant heating/cooling.


What incentives are available?

The Canada Greener Homes Grant Initiative will provide a grant up to $5000 for qualifying energy efficiency improvements to your home, including the installation of a qualified cold climate air source heat pump. You can find all the program details on the federal government program website


Who should I contact about installing a heat pump?

You can find a list of contractors with experience installing air source heat pumps by selecting that option on the Heating, Refrigeration and Air Conditioning Institute of Canada (HRAI) contractor search tool.

However, you should start by arranging a home energy efficiency assessment through the Canada Greener Homes program. The home assessors can help you better understand your home’s needs and help you qualify for incentives.

We are calling on the Government of Ontario to create a program that provides assistance for heat pump installation, including no down payment zero-interest financing. Send a message to Energy Minister Todd Smith supporting our call for action on this important climate measure.


Where can I get more information?

For more detailed information on heat pumps, see this FAQ from Natural Resources Canada

You can also view our webinar recording and the Q&A from the webinar.