What’s the deal with heat pumps?
Heat pumps are a very efficient technology and now with the availability of ductless heat pumps, almost any homeowner can take advantage of them.
How does a heat pump work?
Heat pumps act much like a reverse refrigerator, transferring heat from one place to another. While a fridge transfers heat from inside the fridge to outside to cool the inside space, a heat pump will transfer heat from outside the home to inside.
Heat pumps extract heat from cold outside air and move it inside. This is accomplished when refrigerant absorbs heat in one coil and then is transferred to another coil by a compressor where it releases the heat.
Even when temperatures reach below zero, heat pumps are able to extract and transfer heat. Air at -18°C contains 85% of the heat it contained at 21°C. This means that instead of generating heat like electric baseboards, they can use electricity to give more heat for less cost.
Before investing in a new heating system, also consider other upgrades to your home. A home that is properly draft-proofed and insulated requires less heat than an older drafty home. Adding more insulation reduces the overall amount of heat your home requires and the requirements of the heating unit needed.
We are here to help. We offer rebates to eligible homeowners on home upgrades such as insulation, draft-proofing [what should this link to?], windows and doors and home heating solutions. Also check out our tools and tips to help you select a contractor and find worksheets to evaluate heating systems and quotes.
Types of heat pumps
Heat pumps need a source of heat to transfer from such as the outside air, the ground, or a large body of water. Systems that transfer heat from the ground or water are called “geothermal heat pumps” and systems that transfer heat from the outside air are called “air-source heat pumps”.
A less common type, called an air-to-water heat pump, transfers heat from the outside air to water used for home heating (also called hydronic heating). The hot water is distributed around the home through a system of pipes for in-floor heat. Most air-to-water heat pumps cannot be used for cooling purposes.
The vast majority of heat pumps installed today are air-source, as geothermal heat pumps require deep drilling, large land lots, or permitted access to a body of water.
No matter what the heat source, heat pumps are configured in one of two ways. Ducted heat pumps require ductwork throughout the house to distribute heat from one central location (like a furnace). Ductless heat pumps are installed on a wall and act as a localized heat source, like a wood stove. This type is what most homeowners will be shopping for, especially if their home has electric or hot water baseboard heating.
Comparing efficiencies of different heating systems
As a comparison, most oil-fired furnaces and boilers range between 65-85% efficient, depending on the age and maintenance of the unit. This means that for every $1 of oil you buy, you get anywhere between $0.65 and $0.85 worth of heat, while the rest is lost during the burning of the oil.
Electric heat from baseboards, boilers or furnaces is considered 100% efficient, meaning there is no loss of energy through a combustion process; however the difference in cost between oil heat and electric is not as much as many expect.
Finally, because of the difference in operation, heat pumps normally range between 200-300% efficient as they can supply the same amount of heat using much less energy.
Heat pump system components
There are two components to a ductless heat pump: an outside condenser that looks like a large air conditioning box, and an inside “head” that is mounted high on a wall and blows hot air into the space. Sometimes, based on the size, shape and layout of a home, you may need more than one head to properly heat a home. These could either be attached to one condenser or each attached to their own condenser.
A centrally-ducted system also has an exterior condenser along with a large air handling unit, usually located in a utility room that acts like a furnace. The warm air is distributed around the home via air ducts.
Sizing a heat pump
When you are shopping for a heat pump, we recommend working with a qualified HVAC (heating, ventilation & air conditioning) contractor. They will be able to ensure the unit you purchase is properly sized, properly installed and reliable.
Sizing is the most important factor when choosing a heat pump. There are two ways that someone can size a heat pump, either by the square footage of the house OR through a much more intensive process called a heat load analysis. This involves aspects including the size of the home and each room, the size and placement of each window, the air flow between rooms and floors etc. and requires the use of a computer program. Ensuring your contractor conducts a full heat load analysis will ensure that the unit chosen will perform properly and efficiently.
Cooling With a Heat Pump
While many homeowners are attracted to the cooling ability of heat pumps, remember that it costs the same to cool your home as it does to heat it. To ensure that you don’t accidentally increase your “heating season” and costs through the summer, use your heat pump to cool your home only when needed, ensuring that windows and doors are tightly closed, and only cool to a manageable temperature.