We compare the operation, cost, and efficiency of the air source heat pump to oil and propane systems, as well as ground source heat pumps for use in Canada.
What is an air source heat pump?
An air source heat pump draws in heat from the outdoor air during the winter and expels heat during the summer.
It operates similar to how your traditional air conditioning unit functions, using refrigeration lines to transfer heat from inside to outside – except, an air source heat pump can also heat your home.
In summer, the heat pump rejects heat through its refrigeration system to the outdoor air, leaving the home comfortably cool. In winter, the heat pump reverses its process to extract thermal energy from the air outdoors to circulate around the home.
Heat content of air at -18°C is 85% of that in +21°C
Figures taken from NRCAN
Even when temperatures drop far below zero outside, enough energy remains in the air that it can be extracted, amplified, and used to heat the entire home.
There are two different kinds of technology air source heat pump systems use:
We’ll contextualize the difference with an example:
During the summer, an air to air system will pull heat from inside the home and push it through the pump using an airstream.
In an air to water system, heat from inside the home is pulled from the airstream and forced over a water coil. The chilled water absorbs heat and transports the thermal energy to the heat pump refrigerant circuit which then forces the heat into the outdoor air.
Air source heat pump operating temperatures
These are not like the heat pumps you may have heard of from the 80s which lack efficiency and are only effective in very moderate temperatures. In the last decade, cold climate air source heat pumps have emerged (also known as low temperature air source heat pumps), and this equipment can function at some pretty extreme temperatures.
As temperatures drop to extremes, ice and snow may build up on the outdoor unit. The air source heat pump activates backup heating in the home while it diverts heat to defrosting the ice. This only takes a few minutes before the pump deactivates the backup heating and takes over again.
The best air source heat pumps in Canada can operate down to this temperature
Don’t worry, the heat doesn’t shut off at -25°C! Backup heating (most often electric) will be used to ensure consistent delivery of heat. Efficiency and output capacity of the heat pump are reduced as temperatures approach the minimum operating point.
We’ll explain more below.
How efficient is an air source heat pump?
Furnaces and boilers heat spaces by combusting fuel to warm the air. That means these systems burn fuel (propane, oil, gas) to access the energy within. The efficiency of these systems will always remain below 100% because some energy is always lost through the combustion process.
Heat pumps operate differently. Instead of combusting fuel to access energy, they use electricity to transfer energy. There isn’t the same energy loss that’s present in combustion, instead, a small unit of energy is used to transport much larger quantities of energy from one place to another.
This means that heat pumps, air source and ground source, can operate at efficiencies over 100%. More thermal energy is produced by the heat pump than the amount of energy (electricity) used to power the system.
On average, an air source heat pump can operate with up to 300%, efficiency which means its heating or cooling capacity is triple that of the energy it consumes to generate a temperature change.
But, as it needs to work harder to pull heat out of the air, its efficiency will drop.
If it’s 0°C outside, and your house temperature is set to 25°C, the heat pump only has to accommodate a 25-degree lift. But if it’s -25°C outside, the system must generate a 50-degree lift. To make that happen, the heat pump requires more electricity – which eats into the amount of thermal energy it can move into the home per unit of electricity it uses.
So, in this scenario the heat pump’s efficiency probably isn’t going to be 300%, but more likely between 100 and 150%.
How much does an air source heat pump cost in Canada?
A cold climate air source heat pump, designed and installed to support an entire home, costs an average of $12k – $20k in Canada. This is a larger upfront cost than a traditional furnace or boiler, but it can save you money in the long run. Take a look at the graph below.
Do air source heat pumps save you money?
With an air source heat pump, you pay a larger upfront cost, but your annual energy savings create a return on your investment that keeps paying out over the pump’s 20-year lifetime.
Plus, with an air source heat pump, you’re insulated from rising fuel costs, inflation, and carbon pricing. If you decide not to switch, the money spent on the additional fuel costs for oil or propane becomes money lost on utility overpayment.
While the graph shows natural gas as the cheapest utility, it’s not because of the fuel’s efficiency. Gas suppliers are highly subsidized by all levels of government. However, carbon pricing is set to level the playing field.
As we approach 2030, carbon pricing is set to drastically change the energy market for homeowners. The investment in an independent, clean source of energy will pay off when the bill for fossil fuels skyrockets.
Remember, with a GSHP or ASHP you’re not paying for your energy like you pay for oil or propane, you’re just paying for the electricity to transport it into your home.
Thinking of switching to an air source heat pump in Canada?
The Canada Greener Homes Grant is currently offering up to $5000 rebates on the installation of a cold climate air source heat pump. This rebate is NET, after-tax dollars. Consider how much you have to earn, pre-tax, to get $5000 in your pocket – it’s probably closer to $10,000!
Deciding between ground source and air source?
Air source heat pumps are a great alternative to ground source when your property isn’t favourable to excavation, drilling, or doesn’t have ductwork. But ground-source (geothermal energy) is a clear winner in comfort, efficiency, and durability.
If you’re not sure which is right for you, check out our next blog post for a comparison.
Coming next month.