Quick answer
A whole-home heat pump draws roughly 1 to 4 kilowatts while the compressor runs, and adds several hundred kilowatt-hours a month to a typical Burlington hydro bill through the heating season. The figure depends on the size of the unit, the outdoor temperature, how well the house holds heat, and how often the electric backup heat is called on.
How much electricity a heat pump uses is two numbers: a draw of roughly 1 to 4 kW while the compressor runs, and a consumption of several hundred kilowatt-hours a month through the heating season. Mixing them up is where the confusion starts. The draw is modest, on the order of a couple of space heaters. The consumption is the biggest single line in the house, because unlike a kettle the thing runs for hours at a stretch all winter.
The draw: roughly 1 to 4 kW while running
A residential air-source unit sized for a local two-storey pulls somewhere in the range of one to four kilowatts with the compressor running, and an inverter model spends most of its hours near the bottom of that band. The ceiling is printed on the outdoor unit's data plate as MCA (minimum circuit ampacity) and MOCP (maximum overcurrent protection). That is why these units commonly land on a 30- or 40-amp circuit, often the one the old air conditioner already used, while an electric furnace needs far more.
One kilowatt of electricity buys three to four kilowatts of heat
A heat pump moves heat rather than making it, so the electricity you buy is leverage rather than fuel. Around the freezing mark a cold-climate machine returns roughly three to four units of heat for every unit of electricity it consumes; down near -20°C that ratio falls closer to one and a half or two. Electric baseboards and backup strips are always one for one, no matter the weather. That leverage is the reason the hydro bill climbs less than homeowners brace for.
On a spec sheet the seasonal versions of that ratio are HSPF2 for heating and SEER2 for cooling. More useful when you are estimating consumption is the submittal table, which lists capacity and electrical input at rated outdoor temperatures — usually including -15°C. Ask for that page rather than the glossy brochure.
Turning it into kilowatt-hours for your own house
- Take the rated input in kilowatts at the outdoor temperature you care about, from the manufacturer's submittal sheet.
- Multiply by the hours the unit will actually run that day — near the design temperature, that is most of them.
- As an illustration only: a unit averaging 2 kW that runs 14 hours on a -5°C day consumes about 28 kWh. A month of days like that lands in the several-hundred-kilowatt-hour range.
- Verify it after the fact. Most smart thermostats log runtime by stage, and Burlington Hydro, Oakville Hydro and Alectra each show hourly smart-meter consumption in their online account portals, so a cold week can be compared against a mild one.
Backup heat is what actually moves the bill
The compressor is rarely the expensive part. Electric backup elements are supplied in packages of roughly 5, 10 or 15 kW, and a 10 kW package running for one hour is a flat 10 kWh — several times what the compressor would have used doing the same work. Every hour of unnecessary strip heat is the equivalent of running the heat pump for most of a day.
So a compressor lockout set too warm, or an emergency heat switch left on since last February, turns up as a hydro bill nobody can explain. Check the thermostat before you suspect the equipment — why does my heat pump run constantly walks through separating normal long runtimes from a fault.
The same kilowatt-hours cost different amounts on different plans
Burlington Hydro, Oakville Hydro and Alectra in Hamilton all bill under Ontario's regulated price plans, and you get to pick: tiered, time-of-use, or ultra-low overnight. Heating load is not spread evenly across the clock. The coldest hours are overnight and just before dawn, which is precisely when ultra-low overnight pricing is at its cheapest and time-of-use is off-peak. Winter on-peak windows fall in the morning and again in the early evening — the same hours a thermostat recovering from a deep setback is most likely to fire the strips. Our post on Burlington Hydro rates and heat pumps compares the plans for a heat pump household.
Why two similar houses use different amounts of electricity
- Envelope. A 1950s Aldershot bungalow with thin attic insulation and a leaky rim joist loses heat far faster than a 2000s Alton Village build, and every lost unit has to be bought back.
- Sizing. Undersized equipment leans on strips more nights than it should; the sizing method is covered in what size heat pump do I need.
- Duct routing. Supply trunks crossing an unheated attic or a garage bulkhead dump heat outside the envelope before it reaches a register.
- Defrost frequency. Damp air off Lake Ontario near -2°C frosts a coil faster than dry -15°C air on the escarpment, and each defrost cycle spends energy to buy the coil back.
- Thermostat habits. Steady setpoints suit a heat pump; sharp overnight setbacks hand the recovery to backup heat.
For deeper arithmetic on what a full season costs, see heat pump running cost in Ontario. If you would rather have a number for your house than a range, we bring the manufacturer's rated input and your own heat-loss figure to the quote — see heat pump installation or ask us to look at a year of your bills.