Glossary
Home energy glossary
46 terms you'll see on bills, quotes and spec sheets, explained in plain language.
- ACH50
- ACH50 is the number of times a home's full volume of air leaks out per hour when a blower door depressurizes it to 50 pascals. Lower numbers mean a tighter house, and older homes often test far higher than new ones. Learn more →
- AFUE
- Annual Fuel Utilization Efficiency is the share of a furnace's or boiler's fuel that becomes heat in your home over a year. New gas furnaces in Canada are typically 95% AFUE or higher, while older units can be 60% to 80%. Learn more →
- All-in rate
- The all-in rate is your total electricity bill divided by the kWh you used, so it includes energy, delivery, regulatory charges and fees. It is the most useful number for comparing costs or estimating savings from an upgrade. Learn more →
- Auxiliary / backup heat
- Auxiliary or backup heat is a second heat source, often electric resistance strips or a furnace, that helps a heat pump in very cold weather or during defrost. Electric backup heat has a COP of 1, so frequent use raises bills. Learn more →
- Balance point
- The balance point is the outdoor temperature at which a heat pump alone can just meet your home's heat loss. Below it, backup heat is needed, and a better-sealed home lowers the balance point. Learn more →
- Block heater
- A block heater warms a vehicle's engine so it starts more easily in the cold. Running one all night wastes electricity, and a timer set for 2 to 3 hours before you leave does the same job for much less. Learn more →
- Blower door test
- A blower door test uses a powerful fan in an exterior door to depressurize your home and measure air leakage. It is part of an EnerGuide evaluation and helps find drafts worth sealing. Learn more →
- BTU
- A British thermal unit is a small unit of heat energy, roughly the heat from burning one kitchen match. Furnaces and air conditioners are often rated in BTU per hour, and 3,412 BTU equals 1 kWh. Learn more →
- Coefficient of performance (COP)
- COP is the heat a heat pump delivers divided by the electricity it uses. A COP of 3 means 3 kWh of heat for every 1 kWh of electricity, and COP drops as outdoor temperatures fall. Learn more →
- Cold-climate heat pump
- A cold-climate air-source heat pump is designed to keep heating efficiently in deep cold. Many models keep producing heat to about -25 to -30 °C, which makes them practical as the main heat source in most of Canada. Learn more →
- Cooling degree-day (CDD)
- Cooling degree-days add up how far each day's average temperature rose above 18 °C. They show how much air conditioning a summer or a region typically needs. Learn more →
- Cubic metre of gas (m³)
- Natural gas is billed by the cubic metre (m³) in most of Canada. One m³ contains about 10.35 kWh of energy, which lets you compare gas costs with electricity. Learn more →
- Degradation
- Degradation is the slow loss of a solar panel's output as it ages. Quality panels typically lose about 0.5% per year and carry a 25-year warranty on output. Learn more →
- Delivery charge
- The delivery charge pays to move electricity or gas through the poles, wires and pipes to your home. It often includes a fixed monthly amount plus a per-kWh or per-m³ part, and it can be a large share of a small bill. Learn more →
- Demand charge
- A demand charge bills you for your highest rate of power use (kW) during a billing period, on top of the energy you use. Most Canadian homes do not pay one, but some utilities and rate plans include them for larger services. Learn more →
- Dual-fuel system
- A dual-fuel or hybrid system pairs an electric heat pump with a gas, propane or oil furnace. The heat pump handles milder weather and the furnace takes over when it is very cold or when it is cheaper to run. Learn more →
- Ductless mini-split
- A ductless mini-split is a heat pump with an outdoor unit connected by refrigerant lines to one or more indoor wall or ceiling heads. It suits homes without ducts, such as those heated with baseboards, boilers or oil. Learn more →
- EnerGuide rating
- An EnerGuide home rating, done by a registered energy advisor, estimates your home's yearly energy use in gigajoules and suggests upgrades. Many rebate programs require an evaluation before and after work. Learn more →
- Energy recovery ventilator (ERV)
- An ERV works like an HRV but also transfers some moisture between air streams. It can help keep winter air from getting too dry and summer air from getting too humid. Learn more →
- ENERGY STAR
- ENERGY STAR is a label for appliances, electronics, windows and equipment that meet strict efficiency standards. In Canada it is administered by Natural Resources Canada, and certified products typically use noticeably less energy than standard models. Learn more →
- Gigajoule (GJ)
- A gigajoule is a unit of energy used on some gas bills and in EnerGuide ratings. One GJ equals about 278 kWh, or roughly 26.8 m³ of natural gas. Learn more →
- Ground-source heat pump
- A ground-source or geothermal heat pump moves heat to and from the ground through buried pipe loops. It is the most efficient heating option, with a seasonal COP around 3.5 or higher, but installation costs much more than an air-source system. Learn more →
- Heat pump water heater
- A heat pump water heater pulls heat from the surrounding air to warm water in a tank. It typically uses about half to a third of the electricity of a standard electric tank. Learn more →
- Heat recovery ventilator (HRV)
- An HRV brings in fresh outdoor air and exhausts stale indoor air while transferring heat between the two streams. It keeps tight homes healthy without throwing away most of the heat in the air it removes. Learn more →
- Heating degree-day (HDD)
- Heating degree-days measure how cold a period was by adding up how far each day's average temperature fell below 18 °C. More degree-days means more heating demand, so they help compare winters and locations fairly. Learn more →
- HSPF / HSPF2
- The Heating Seasonal Performance Factor rates a heat pump's heating efficiency over a whole season. HSPF2 is the newer test standard and gives lower numbers than the old HSPF for the same unit, so compare like with like. Learn more →
- Inverter (solar)
- A solar inverter converts the direct current (DC) from panels into alternating current (AC) your home and the grid use. A string inverter handles a group of panels at once and is usually replaced once during a system's life. Learn more →
- Kilowatt (kW)
- A kilowatt measures power, or how fast energy is used or produced at a given moment. Solar systems, heat pumps and EV chargers are rated in kW, while the energy they use or make over time is counted in kWh. Learn more →
- Kilowatt-hour (kWh)
- A kilowatt-hour is the unit your electricity bill uses to measure energy. It equals using 1,000 watts for one hour, such as a 1,000-watt space heater running for an hour. Learn more →
- kWp, DC vs AC
- kWp (kilowatt-peak) or kW DC is the total rated output of your panels under test conditions. kW AC is the inverter's output limit, which is often a bit lower, so check which number a quote uses when comparing price per watt. Learn more →
- Level 2 charger
- A Level 2 charger runs on a 240-volt circuit and charges an EV several times faster than a standard wall outlet. Most owners charge overnight at home and add a typical day's driving in a few hours. Learn more →
- Levelized cost
- Levelized cost spreads the full lifetime cost of a system over all the energy it will produce or save, giving a cost per kWh. For solar, you can compare it directly with your all-in electricity rate. Learn more →
- Microinverter
- A microinverter is a small inverter mounted under each solar panel. It limits the effect of shade on one panel and allows panel-level monitoring, usually at a higher upfront cost than a string inverter. Learn more →
- Net billing
- Net billing credits solar power you export to the grid at a set rate that is often lower than what you pay to buy electricity. Under net billing, using your solar power yourself is worth more than exporting it. Learn more →
- Net metering
- Net metering lets solar owners send extra electricity to the grid and receive bill credits for it, usually at or near the retail rate. Credits typically roll over month to month, with rules that vary by province and utility. Learn more →
- Payback period
- The payback period is how many years an upgrade takes to save as much as it cost. It is a simple way to compare options, though it ignores savings after payback and the cost of borrowing. Learn more →
- Phantom load
- Phantom or standby load is the power electronics and appliances draw when switched off or idle. It typically adds up to a few percent of a home's electricity use and can be cut with power bars and settings. Learn more →
- R-value
- R-value measures how well insulation resists heat flow in imperial units. Higher numbers insulate better, and attics in most of Canada are typically upgraded to about R-50 or R-60. Learn more →
- RSI
- RSI is the metric version of R-value used in Canadian building codes. To convert, multiply RSI by about 5.68 to get R-value, so RSI 8.8 is roughly R-50. Learn more →
- SEER / SEER2
- The Seasonal Energy Efficiency Ratio rates an air conditioner's or heat pump's cooling efficiency over a season. Higher is better, and SEER2 is the updated test method that produces slightly lower numbers than SEER. Learn more →
- Solar yield
- Solar yield is how many kWh a system produces per installed kW each year. In populated parts of Canada it is roughly 1,000 to 1,350 kWh per kW, with the Prairies at the high end. Learn more →
- Tiered pricing
- Tiered pricing charges one rate for your first block of electricity each month and a higher rate once you pass that threshold. The rate does not change with the time of day. Learn more →
- Time-of-Use (TOU)
- Time-of-Use pricing charges different electricity rates depending on the time of day and day of the week. Power is cheapest overnight and on weekends and most expensive on weekday peak hours. Learn more →
- Tonnage
- Tonnage describes the size of an air conditioner or heat pump, where one ton equals 12,000 BTU per hour of capacity. Most Canadian homes use systems between about 1.5 and 5 tons, sized by a proper load calculation. Learn more →
- U-factor
- U-factor measures how much heat passes through a window or door, so lower is better. It is roughly the inverse of R-value, and ENERGY STAR windows for colder Canadian zones have low U-factors. Learn more →
- Ultra-Low Overnight (ULO)
- Ultra-Low Overnight is an Ontario price plan with a very cheap overnight rate and a higher weekday afternoon peak rate. It suits homes that can shift EV charging, laundry or water heating to the night. Learn more →