HVAC Glossary Ontario 2026
By the Get a Better Quote Research Team. Last verified: April 14, 2026.
This glossary covers the HVAC, efficiency, regulatory, and rebate terms Ontario homeowners run into when replacing a furnace, air conditioner, heat pump, or water heater in 2026. Every entry is written in plain English and, where it matters, points to the Ontario regulator, program, or cost guide behind the term. Use it as a quick reference when reading quotes, rebate paperwork, or our cost guides.
AFUE
Annual Fuel Utilization Efficiency. The percentage of fuel a gas or propane furnace actually converts into usable heat over a full heating season. A 96% AFUE furnace delivers 96 cents of heat for every dollar of gas, with the rest lost up the flue. As of 2026, ENERGY STAR certified gas furnaces in Canada must typically reach 96% AFUE or higher. Mid-efficiency furnaces from the 1990s commonly ran 78% to 82%, which is why replacements usually pay back in reduced gas use.
SEER2
Seasonal Energy Efficiency Ratio, version 2. The 2026 standard for rating central air conditioner and heat pump cooling efficiency, replacing the older SEER rating with a more realistic test procedure that reflects actual duct static pressure. Higher is better. Most new central AC units sold in Ontario fall between SEER2 14.3 and SEER2 20. SEER2 ratings run roughly 4.5% lower than the old SEER number for the same equipment, so a 16 SEER unit is close to a 15.2 SEER2 unit.
HSPF2
Heating Seasonal Performance Factor, version 2. The companion rating to SEER2 for heat pump heating efficiency, updated in 2026 to reflect realistic test conditions. Higher is better. Typical cold-climate heat pumps sold in Ontario rate between HSPF2 8 and HSPF2 10 in the colder Region IV climate zone, which most of Ontario falls into. HSPF2 numbers run roughly 15% lower than the older HSPF for the same equipment.
ASHP
Air-Source Heat Pump. A heat pump that extracts heat from outdoor air in winter and rejects heat to outdoor air in summer, providing both heating and cooling from a single outdoor unit. Standard air-source heat pumps lose most of their heating capacity below about -10 C, which is why cold-climate variants (see ccASHP) are usually required for Ontario winters. ASHPs are the most common heat pump type installed in Ontario today.
ccASHP
Cold-Climate Air-Source Heat Pump. A subset of ASHPs engineered with variable-speed compressors, enhanced vapor injection, and larger outdoor coils so they maintain useful heating capacity at temperatures as low as -25 C to -30 C. NRCan publishes a list of cold-climate certified models that qualify for federal and Ontario rebate programs. For most of Ontario, a ccASHP is the appropriate choice if a home is converting from gas or oil.
GSHP
Ground-Source Heat Pump, also called a geothermal heat pump. Extracts heat from the ground through buried loops of pipe filled with a water-glycol mixture, then uses a heat pump refrigeration cycle to deliver that heat indoors. Ground temperatures in Ontario stay near 8 C to 10 C year-round below the frost line, so GSHPs deliver very stable efficiency. Installation cost is typically 2 to 3 times that of an ASHP because of the loop field, which limits adoption to larger or rural properties.
COP
Coefficient of Performance. The ratio of heat energy delivered to electrical energy consumed by a heat pump. A COP of 3 means the unit delivers three units of heat for every one unit of electricity. Heat pump COP falls as outdoor temperature drops: a cold-climate ASHP might run at COP 3.5 at 8 C, COP 2.5 at -8 C, and COP 1.8 at -25 C. COP is the instantaneous measurement; HSPF2 is the seasonal average.
BTU
British Thermal Unit. The standard North American unit of heat energy, defined as the heat required to raise one pound of water by one degree Fahrenheit. HVAC equipment is usually rated in BTU per hour (often shortened to just BTU on spec sheets). A typical Ontario home needs somewhere between 30 and 45 BTU per square foot per hour of heating capacity, but the accurate number comes from a CSA F280 or Manual J load calculation.
Ton
An HVAC capacity unit equal to 12,000 BTU per hour of cooling. The term comes from the amount of heat needed to melt one ton of ice in 24 hours. Residential central air conditioners in Ontario commonly range from 1.5 tons (18,000 BTU/hr) for small homes up to 5 tons (60,000 BTU/hr) for large homes. A properly sized 2,000 square foot Ontario home typically needs 2.5 to 3.5 tons of cooling.
ERV
Energy Recovery Ventilator. A mechanical ventilation device that exchanges stale indoor air with fresh outdoor air while transferring both heat and moisture between the two streams. The moisture transfer is what distinguishes an ERV from an HRV, making ERVs better suited to homes with air conditioning and humidity concerns in summer. In Ontario, ERVs and HRVs are often used interchangeably for new builds and retrofits targeting tighter air sealing.
HRV
Heat Recovery Ventilator. Similar to an ERV but transfers only heat between incoming and outgoing air streams, not moisture. HRVs are the more common choice in Ontario retrofits because they perform well in cold, dry winter conditions where latent heat recovery matters less. The Ontario Building Code requires mechanical ventilation in all new homes, and HRVs are the most common way builders meet that requirement.
Manual J
The US residential HVAC load calculation standard published by the Air Conditioning Contractors of America. A Manual J calculation adds up heat loss and heat gain for every wall, window, door, ceiling, and floor in a home, plus infiltration and internal loads, and returns a whole-house heating and cooling load in BTU per hour. Widely used by Ontario contractors because the software is common. See the HVAC sizing guide for how CSA F280 compares.
Manual D
The ACCA standard for residential duct design. Where Manual J tells you how much heating and cooling each room needs, Manual D tells you how to size, route, and balance ductwork so each room actually receives its share of conditioned air. Poor duct design is the second most common cause of comfort complaints in Ontario homes after oversized equipment. Manual D is rarely done for retrofit work, which is one reason many older homes have uneven room temperatures.
Manual S
The ACCA standard for selecting HVAC equipment once the Manual J load is known. Manual S provides the rules for matching calculated heating and cooling loads to actual equipment capacities, including how much oversizing is acceptable. For central air conditioners, Manual S typically allows cooling equipment up to 115% of calculated load. For heat pumps in Ontario, Manual S guides the balance point decision and backup heat sizing.
MERV
Minimum Efficiency Reporting Value. A rating scale from 1 to 16 that measures how effectively an air filter captures airborne particles. A MERV 8 filter (common for builder-grade systems) captures dust, lint, and pollen. MERV 11 to 13 captures finer particles like mold spores and some bacteria, and is the range most often recommended for Ontario homes with allergy concerns. Filters above MERV 13 can restrict airflow on older systems and should be matched to blower capacity.
Balance Point
The outdoor temperature at which a heat pump's heating capacity exactly matches the home's heat loss. Above the balance point, the heat pump handles the load on its own. Below it, backup heat (electric resistance or a gas furnace) kicks in to cover the gap. For Ontario homes with cold-climate heat pumps, balance points commonly fall between -10 C and -20 C depending on equipment sizing, home insulation, and whether the design prioritizes upfront cost or annual operating cost.
Dual-Fuel System
A hybrid HVAC setup pairing an electric heat pump with a gas furnace as backup heat. The heat pump handles mild and moderate weather where it is more efficient than gas, and the furnace takes over below the balance point where gas becomes cheaper per BTU. Dual-fuel is increasingly popular in Ontario because it offers the rebate eligibility and efficiency of a heat pump without removing the security of a gas furnace during extreme cold.
Variable-Speed
A blower motor or compressor that can run at many speeds rather than simply on or off. Variable-speed blowers (often called ECM or inverter motors) ramp up and down smoothly to match demand, reducing noise, improving humidity control, and using less electricity. Variable-speed compressors in heat pumps and air conditioners modulate cooling and heating output in small increments, typically improving seasonal efficiency by 15% to 30% compared to single-stage equipment.
Two-Stage
A compressor or furnace burner with two output levels, usually around 65% to 70% of full capacity (low stage) and 100% (high stage). Two-stage equipment runs in low stage most of the time, which is quieter, more efficient, and gives better humidity control in cooling mode than single-stage. High stage only engages during the coldest or hottest hours. Two-stage is a middle ground between single-stage and fully variable-speed equipment.
Zone Damper
A motorized flap installed inside a duct that opens or closes to direct airflow toward specific rooms or zones. Zone damper systems let a single furnace or heat pump serve multiple zones with independent thermostats, so you can run the upstairs cooler than the basement or turn off heat to unused rooms. Zoning works best on new ductwork designed for it, and retrofit zoning on older systems sometimes creates airflow problems unless a bypass is added.
R-410A
A hydrofluorocarbon refrigerant that has been the industry standard for residential heat pumps and air conditioners in Canada since the early 2000s. R-410A has a high global warming potential, and Canadian regulations began phasing it out of new equipment starting in 2025, with most new central systems moving to R-454B by 2026. Existing R-410A equipment can still be serviced, but supply of the refrigerant will tighten over the rest of the decade.
R-454B
An A2L-classified refrigerant (mildly flammable, lower global warming potential) that is replacing R-410A in most new residential heat pumps and air conditioners sold in Canada from 2026 onward. A2L refrigerants require updated safety practices during installation and service, and older technicians may need retraining. Homeowners do not typically need to do anything differently once R-454B equipment is installed, but service calls may cost slightly more during the transition years.
TSSA
Technical Standards and Safety Authority. The Ontario regulator responsible for licensing and inspecting gas work, including natural gas and propane furnaces, water heaters, and gas piping. Any work on gas-fired HVAC equipment in Ontario must be performed by a TSSA-licensed gas technician. TSSA also investigates gas incidents and maintains the public register of licensed fuels contractors. Homeowners can verify a contractor's gas license directly on the TSSA website.
HRAI
Heating, Refrigeration and Air Conditioning Institute of Canada. The national industry association for HVAC contractors, distributors, and manufacturers. HRAI runs training programs, publishes technical standards used across the industry, and its contractor membership is often treated as a baseline quality signal. HRAI membership is not a license and does not replace TSSA or ESA credentials, but it usually indicates a contractor who takes training and industry practices seriously.
ESA
Electrical Safety Authority. The Ontario regulator responsible for electrical inspections and licensing of electrical contractors. Any electrical work connected to HVAC equipment (new circuits for heat pumps, panel upgrades, disconnects) must be performed by an ESA-licensed electrical contractor and is subject to an ESA inspection. Heat pump installations in Ontario commonly require ESA notifications because of the new dedicated circuits involved.
313A
Ontario's Residential Air Conditioning Systems Mechanic trade code. A 313A is the journeyperson certification issued by Skilled Trades Ontario for technicians who install and service residential cooling and heat pump equipment. Good HVAC companies employ or contract 313A-certified mechanics for installations. The 313A ticket is distinct from TSSA gas certifications, so a full heat pump install on a gas-heated home may involve both a 313A mechanic and a G1 or G2 gas technician.
G1 / G2
Ontario's TSSA gas technician certifications. A G2 technician is licensed to install and service most residential and light commercial gas appliances up to 400,000 BTU per hour, which covers nearly every home furnace, boiler, and water heater. A G1 is the senior certification, covering all gas equipment with no BTU limit. For a typical Ontario home gas furnace install, a G2 is sufficient. Always confirm the technician on site holds a valid TSSA card, not just the company.
NOSI
Notice of Security Interest. A registration on title under Ontario's Land Titles Act that flags a financed or rented piece of home equipment (commonly a water heater, HVAC system, or solar install) as belonging to the financing company. A NOSI does not stop a home sale but can complicate the closing because buyers or their lawyers often want it removed or assigned. Ontario's Bill 200 changed the NOSI framework significantly in recent years, so always check current Land Titles Act rules.
Cooling-Off Period
Under section 43 of Ontario's Consumer Protection Act, a consumer has 10 calendar days after signing a direct-agreement sales contract (door-to-door or in-home sale) to cancel for any reason without penalty. HVAC and water heater contracts sold in your home generally qualify. Cancellation must be in writing, and the 10-day clock starts from the day the consumer receives the written copy of the contract. This is a statutory right and cannot be waived.
HRS
Home Renovation Savings. The Save on Energy program administered by the Independent Electricity System Operator (IESO) that provides Ontario homeowners with rebates on eligible energy-efficient home upgrades, including heat pumps, insulation, windows, and smart thermostats. HRS replaced earlier Ontario rebate programs and is the main provincial rebate pathway in 2026. Program terms, rebate amounts, and eligible measures are updated periodically; always check the current official Save on Energy website.
HER+
Home Efficiency Rebate Plus. The Enbridge Gas rebate program for Ontario homeowners who completed an EnerGuide pre-audit, undertook energy retrofits (insulation, air sealing, heat pump, windows, or water heater), and completed a post-audit. HER+ closed to new applications in December 2025 and was among the most generous provincial efficiency incentives while it ran. Ontario homeowners now apply through the Home Renovation Savings (HRS) program instead, and any active-tense references to HER+ for 2026 projects are out of date.
CGHAP
Canada Greener Homes Affordability Program. The federal follow-on initiative from NRCan aimed at lower and middle-income households after the original Canada Greener Homes Grant wound down. CGHAP focuses on heat pump conversions and deep retrofits for eligible homes, with program terms that vary by household income and region. Program details, eligibility thresholds, and funding caps are set by NRCan and updated periodically, so always check the current NRCan page before planning a project around it.
UEF
Uniform Energy Factor. The US Department of Energy efficiency rating for water heaters, which replaced the older Energy Factor (EF) rating. UEF accounts for standby losses and real-world usage patterns. A UEF of 0.95 for a gas tank water heater is considered high efficiency; heat pump water heaters commonly rate between UEF 3.0 and UEF 4.0, meaning they deliver three to four times as much hot water per unit of electricity as a straight resistance tank.
EnerGuide
The Natural Resources Canada home energy rating system. An EnerGuide evaluation is performed by a registered energy advisor who uses a blower door test and a walkthrough to model a home's energy use, then issues a rating and a list of recommended upgrades. EnerGuide pre-audits and post-audits are required to qualify for several Ontario and federal rebate programs (including HER+ and historically the Canada Greener Homes Grant). A full evaluation typically costs a few hundred dollars before rebates.
Ontario Building Code
Ontario Regulation 332/12, the provincial regulation that sets minimum construction standards for new homes and major renovations in Ontario, including insulation levels, air tightness, mechanical ventilation, and HVAC sizing methodology. The OBC references CSA F280 for residential HVAC load calculations and sets minimum efficiency requirements for new equipment. Retrofits in existing homes are not usually held to new-construction OBC standards, but permitted work must meet the code in force at the time of the permit.