Air Source Heat Pump Space Heating and Cooling

Pie charts of residential emissions
Residential GHG emissions by end use (left) and energy source (right)
Source: NRCan

THE HOUSEHOLD GREENHOUSE GAS PROBLEM

Space heating accounts for 60% of residential energy consumption across Canada, more than water heating, air conditioning, appliances and lighting combined. At the same time, nearly 50% of residential energy Canada-wide comes from natural gas.

Natural gas has a high carbon footprint—in other words, it creates a lot of greenhouse gas (GHG) emissions. That is why one of the best ways to reduce your household carbon emissions is to move away from natural gas.

More

A SOLUTION: AIR SOURCE HEAT PUMPS

Air source heat pumps (ASHPs) are high-efficiency appliances that run on electricity rather than natural gas. They can also provide both heating and cooling – a definite bonus.

High-efficiency ASHPs offer deep GHG reductions. One Harbord Village homeowner was able to cut their GHG emissions by 87% by replacing their gas furnace with a cold climate ASHP system in combination with other building envelope upgrades that reduced their heat load.

__
SHOULD YOU CONSIDER AN ASHP?

Should you retrofit your home heating system with an ASHP? If so, how much will it cost? How much will your emissions go down? The answer to these questions will depend on a number of factors and may vary from household to household.

  • The age of your home’s current heating and air-conditioning systems
  • The type of heating and air-conditioning systems you currently have
  • Your motivation and budget

More

The age of your home’s current heating system
You should consider an ASHP (or plan ahead to install one) if your furnace is more than 15 years old. Even if your furnace is newer, it could be time to replace an old air-conditioning unit with an ASHP.
Homeowner with old furnace left and old AC right

The type of heating system you currently have
You will have different ASHP choices depending on your home’s current heating system. See the HOW ASHPs WORK section below for more details.

Homeowner with rads left and electric heat right <;!╌ ---------- PERSONAS 3,4 IMAGE ---------- ╌>

Your motivation and budget
Your choice of ASHP system will determine overall emissions reductions, up front and operating costs, and could even impact the availability of government rebates.

Homeowner motivated by emissions left and cast right

__
COSTS AND REBATES

In general, the sticker price of a new ASHP will be higher than a conventional furnace or boiler. Costs range from $5,000 for a Mitsubishi low-temperature ductless heat pump to $19,500 for a Mitsubishi cold climate unit. The operational costs of the most efficient ASHP are equal to those of a gas furnace and old fashioned air conditioning.

The following information comes from real life case studies of ASHP retrofits in Toronto:

System typeCut off temp.
(degrees C)
Equipment cost
relative to conventional
GHG emissions
reductions
Cold climate ASHP with electric backup-20$ + ~$8000Maximum
Hybrid ASHP with gas furnace backup-5$ + ~$2000Medium
Conventional furnace or boilerNA$None

More

There may be additional cost considerations. For example:

  • The more you can improve your home insulation, the more you will reduce your heat load, equipment cost and carbon footprint
  • It may be necessary to upgrade your electrical service to 200amps
  • COVID and supply chain issues could impact supply and installation costs

REBATE PROGRAMS AND INCENTIVES

Fortunately, a number of rebate and loan programs can help make ASHPs more affordable.

  • Federal Government Greener Homes Program (up to $5,000 rebate)
  • Enbridge Home Efficiency Rebate Program
  • City of Toronto Home Energy Loan Program
  • Income Based Programs

Some of these programs require a home energy audit by a certified home energy advisor. Be sure to complete this home assessment before starting renovation and retrofit work in order to qualify for a rebate.

NB: not all ASHP makes and models qualify for the Greener Homes rebate. Refer to NRCan’s list of qualifying makes and models to confirm whether yours will.

To learn more about ASHP retrofits for our older homes in the Harbord Village, watch The ABCs of Heat Pumps, a webinar featuring Trish Long of Goldfinch Energy and Steve Cornelius of Mitsubishi Electric.

__
HOW ASHPs WORK

An ASHP captures heat from outside air and transfers it indoors in order to heat your house in winter. Even very cold outside air contains some heat that an ASHP can capture, making it possible to heat your home in low temperature conditions.

Diagram of air source heat pump in winter
How ASHPs transfer heat from the outdoors to the indoors in winter
Source: NRCan

More

How is it possible to capture heat from very cold air? Think of how your refrigerator operates. Thanks to its compressor, it continuously removes heat from the cool fridge interior–enough to maintain cold temperatures in the cooling compartment–and even sub-zero temperatures in the freezer. Think of an ASHP as a refrigerator for your house that keeps it cool in summer. In winter, an ASHP operates in reverse mode to keep the house warmer than outdoors.

Although ASHPs run on electricity, they are not like your grandfather’s electric baseboard heaters. Baseboard heaters consume a lot of electricity to create heat. ASHPs, by comparison, use a relatively small amount of electricity to run a compressor. This distinction is what makes ASHPs so much more efficient than conventional electric resistance heaters.

ASHP SYSTEM REQUIREMENTS

An ASHP system has two main components:

  • Outdoors: a compressor located on an outside wall of the house or on a flat roof
  • Indoors: a heat transfer unit, which can take different forms depending on existing conditions. In the case of a house with a forced air heating system, a fan unit would replace the furnace and the ductwork would be used for distribution of heat or cooling. In the case of a house with a boiler and rads, an air-to-water heat exchanger would transfer heat to the hot water pipes and rads. In this case, AC could be added (if desired) by installing one or more fan units in the house. A fan unit could replace an existing floor mounted rad, or be a separate ceiling mounted unit.
  • NB: different types of hot water heating systems (cast iron rads, thin wall rads, in-floor radiant heat) operate at different temperatures. Ensure your new ASHP system is designed to work with the type of hot water system in your house. The manufacturer and installer should be able to assist.

__
WHAT TO LOOK FOR WHEN SHOPPING FOR AN ASHP

‘Cold climate’ heat pumps (CCHP) are the state of the art, providing heat right down to -20 to -25 C. They may be more expensive but also qualify for the larger Greener Homes rebates.

The efficiency of all heat pumps decreases in tandem with the outside air temperature. Winters in Ontario can be cold enough that a backup heating system is recommended in order to provide heat on those few really cold days when outside air temperatures drop below the minimum design temperature of your ASHP, whether it is cold climate or not. Backup systems can be gas fired or electric. However, the best way to minimize your GHG emissions is to choose electric.

Modulating fans operate continuously (as opposed to single-stage on/off fans that cut in and out). As a result, they can be less expensive to run and more comfortable.

It is important for the heating system to be right-sized–-not over-sized or under-sized–-for your home. Your installer should be able to calculate your home’s heat load, taking into account any planned building envelope upgrades.

More

MANUFACTURERS

There are many ASHP makes and models. For example:

*NB: HVRA does not endorse or guarantee any particular manufacturer or installer and has no financial ties to any of them.

___
** Illustration credits:
Heads: Yu Luck, Noun Project
Radiator: Fabio, Noun Project
Footprints: Puput Nugroho, Noun Project