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kWh vs kW Explained: What Your Ontario Hydro Bill Is Measuring

kWh vs kW explained in plain language: power versus energy, how to work out what an appliance costs to run in Ontario, and how tons, BTUs and m³ compare.

Energy Efficiency Ontario Editorial Team Updated 6 min read

Key takeaways

  • A kilowatt (kW) measures power, the rate of use at a moment; a kilowatt-hour (kWh) measures energy, the amount used over time.
  • Ontario residential electricity bills charge by the kWh, not by peak kW demand.
  • Cost to run something = kW × hours = kWh, then kWh × your price per kWh.
  • A 1.5 kW space heater running for 4 hours uses 6 kWh, roughly 55¢ of electricity at the 9.1¢ off-peak price before delivery and other charges.

The difference between kWh vs kW is the difference between how much and how fast. A kilowatt (kW) is a rate of power, like the speed of a car, while a kilowatt-hour (kWh) is an amount of energy, like the distance travelled; your Ontario hydro bill charges you for kWh.

Once that clicks, it becomes easy to estimate what any appliance costs to run, compare heating options, and read solar or heat pump quotes with confidence.

kWh vs kW: what is the difference?

  • Watt (W): the basic unit of power. A typical LED bulb draws about 9 W.
  • Kilowatt (kW): 1,000 watts. A kettle draws roughly 1.5 kW while it is on.
  • Kilowatt-hour (kWh): using 1 kW for one hour. It is also 100 W for 10 hours, or 2 kW for 30 minutes.

The formula is simple:

kW × hours of use = kWh

A 1.5 kW kettle that runs for 4 minutes (0.067 hours) uses about 0.1 kWh. A 9 W LED bulb on for 5 hours a day uses 0.045 kWh a day, or roughly 16 kWh a year. Same unit, very different scale.

Tip: The wattage is usually printed on the appliance label or the power adapter. If only amps (A) and volts (V) are listed, multiply them: watts ≈ volts × amps. A 120 V device drawing 10 A uses about 1,200 W, or 1.2 kW.

How do you calculate what an appliance costs to run in Ontario?

Multiply the kWh by your price. Under the Regulated Price Plan from 1 November 2026, Time-of-Use (TOU) commodity prices are 9.1¢ off-peak, 14.6¢ mid-peak and 18.9¢ on-peak. Those are commodity prices only; delivery, regulatory charges and HST are added, and the Ontario Electricity Rebate (15.7%) is subtracted. For a typical Toronto-area home on TOU, the all-in cost works out to roughly 15–19¢ per kWh before the rebate. That is an estimate; delivery charges vary by utility.

The table uses typical power draws and an example all-in price of 14¢/kWh after the rebate. Your actual numbers will differ.

Appliance Typical power (kW) Example use Energy (kWh) Approx. cost at 14¢/kWh
LED bulb 0.009 5 h/day for a year 16 $2.30/year
Portable space heater 1.5 4 h/day for a month 180 $25/month
Electric clothes dryer 2.5–4 kWh per load 5 loads/week for a year 650–1,040 $90–$145/year
New ENERGY STAR fridge runs on and off All year 350–450 $50–$65/year
Pre-2000 fridge runs on and off All year 1,000+ $140+/year
EV, 15,000 km/year 7.2 (Level 2 charger) 16–20 kWh/100 km 2,400–3,000 $335–$420/year (less on ULO overnight)

For a quick estimate with your own numbers, use our appliance energy cost calculator. For the whole bill, including delivery and regulatory charges, try the hydro bill estimator.

Appliances such as fridges, freezers and heat pumps cycle on and off, so their nameplate wattage overstates the energy they use. For those, the EnerGuide label's annual kWh figure is more reliable than wattage × 24 hours.

Does Ontario charge homeowners for kW demand?

No. Residential customers on the Regulated Price Plan are billed on kWh used, with prices that change by time of day under TOU or ULO. Many commercial customers do pay demand charges based on their highest kW draw in a month, which is why you may see kW on business bills.

kW still matters at home in two practical ways:

  1. Your electrical service. Your panel and service size (for example, 100 A or 200 A) limit how many kW you can draw at once. At 240 V, a 100 A service can supply about 24 kW in theory, but electricians plan for continuous loads well below that. Adding a heat pump, Level 2 charger and induction range at once can push an older home toward an upgrade. See our panel upgrade guide.
  2. When you use it. Running a 7 kW EV charger during a ULO on-peak window (weekdays 4–9 p.m. at 37.7¢) costs about ten times more per kWh than the same charge overnight at 3.7¢.

How do kW and kWh relate to heating, solar and gas?

Energy shows up in other units around the house. These conversions help you compare them.

Unit What it measures Conversion
BTU/h Heating or cooling power (common on furnaces and ACs) 1 kW ≈ 3,412 BTU/h
Ton (cooling or heat pump capacity) Heating or cooling power 1 ton = 12,000 BTU/h ≈ 3.5 kW
Cubic metre (m³) of natural gas Energy in the gas 1 m³ ≈ 10.35 kWh (≈ 37.3 MJ)
Gigajoule (GJ) Energy (used on EnerGuide home ratings) 1 GJ ≈ 278 kWh
kW of solar (kWdc) Peak panel power under test conditions In southern Ontario, each kW typically yields roughly 1,100–1,250 kWh per year if well oriented and unshaded

A useful comparison: a 3-ton heat pump has a heating capacity of roughly 10.5 kW at mild temperatures. With a coefficient of performance (COP) of 3, it delivers that heat while drawing only about 3.5 kW of electricity. An electric baseboard heater has a COP of 1: every kW of electricity becomes one kW of heat.

For gas, a 95% efficient furnace turns each m³ into roughly 9.8 kWh of delivered heat. At an example price of 45¢/m³, that is about 4.6¢ per kWh of heat. Comparing fuels this way, per kWh of heat delivered, is the basis of our heat pump vs furnace calculator.

Where do you find kWh on your bill and smart meter data?

Your bill lists total kWh used in the billing period, usually split into off-peak, mid-peak and on-peak (or ULO periods, or Tier 1 and Tier 2). Most Ontario utilities also let you download hourly smart meter data through their online portal, often in Green Button format. Hourly data is measured in kWh per hour, which is the same as average kW for that hour, so you can see when your home's demand peaks.

Our guide to reading your hydro bill explains each line, and the glossary defines terms like kVA and power factor that sometimes appear in equipment specs.

Frequently asked questions

Is a kWh the same as a kW per hour?

No. "kW per hour" would describe how fast power is changing, which is rarely useful at home. A kWh is kW multiplied by hours: power sustained over time.

How many kWh does an Ontario home use?

A home without electric heat typically uses roughly 650–800 kWh a month, or 7,000–9,000 kWh a year. The OEB uses 700 kWh a month as its typical residential customer for bill comparisons. Homes heated by heat pumps or baseboards often use 12,000–20,000 kWh a year or more.

Why does my solar quote list both kW and kWh?

The kW figure is the system size (peak panel power). The kWh figure is the estimated energy it will produce over a year, which is what affects your bill. Two systems with the same kW can produce different kWh depending on roof direction and shading.

What does a 1.5 kW space heater cost to run in Ontario?

It uses 1.5 kWh for every hour on high. At an all-in example price of 14¢/kWh, that is about 21¢ an hour, or roughly $25 a month at 4 hours a day.

About this page. Written and reviewed by the Energy Efficiency Ontario editorial team using official sources including the Ontario Energy Board, Save on Energy (IESO), Enbridge Gas and Natural Resources Canada. Figures are estimates unless attributed. Program terms change — confirm with the administrator before you buy. Our editorial standards · Report an error

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