We worked out the cost per hour on every Ontario price plan and Quebec’s Rate D, then priced two common uses: a bedroom heater overnight and a home office heater during the workday.

The short answer

A 1,500-watt space heater on full power uses 1.5 kWh an hour. In Ontario that costs about 13.7¢ an hour off-peak on Time-of-Use, 21.9¢ mid-peak and 28.4¢ on-peak, for the electricity alone. Run it 8 hours a night for a month and you pay $13.32 on Ultra-Low Overnight, $32.76 on Time-of-Use or $40.32 to $47.52 on Tiered pricing.

The formula is simple: watts divided by 1,000, times hours, times your price per kWh. Use the calculator with your own heater and plan.

What a space heater costs per hour

The Ontario Energy Board sets the Time-of-Use (TOU), Ultra-Low Overnight (ULO) and Tiered prices. The prices below took effect on November 1, 2026, according to the OEB electricity rates page. Quebec prices are from Hydro-Québec’s Rate D, effective April 1, 2026.

Cost per hour = 1.5 kWh x price per kWh, rounded to one decimal. Prices cover the Electricity line only.

When each price applies in winter

• TOU: off-peak weekdays 7 p.m. to 7 a.m. and all day on weekends and holidays; mid-peak weekdays 11 a.m. to 5 p.m.; on-peak weekdays 7 to 11 a.m. and 5 to 7 p.m.
• ULO: ultra-low overnight every day 11 p.m. to 7 a.m.; weekend off-peak 7 a.m. to 11 p.m.; mid-peak weekdays 7 a.m. to 4 p.m. and 9 to 11 p.m.; on-peak weekdays 4 to 9 p.m.
• Tiered: the lower price covers the first 1,000 kWh a month from November 1 to April 30.
• Quebec Rate D: the lower price covers up to 40 kWh a day times the days in your billing period.

The gap is wide. The same heater for the same hour costs about ten times as much on ULO on-peak (56.6¢) as on ULO overnight (5.6¢). When you run it matters as much as how long.

Two worked examples

A bedroom heater, overnight

Say you run a 1,500-watt heater on full power from 11 p.m. to 7 a.m. every night for 30 nights. That is 1.5 kWh x 8 hours x 30 nights, or 360 kWh. Those hours are all in ULO’s cheapest period and TOU’s off-peak period, so the plan you are on decides the bill.

On ULO, the month costs $13.32. On TOU it costs $32.76, about $19 more. On Tiered, it costs $40.32 if the extra 360 kWh stays inside your first 1,000 kWh, or $47.52 if all of it lands in Tier 2. These figures are hypothetical and assume full power all night.

A home office heater, weekdays 9 to 5

Now take the same heater run from 9 a.m. to 5 p.m. on 21 weekdays, which uses 252 kWh in the month. Daytime is when ULO is least friendly.

• Tiered: $28.22 at the Tier 1 price, or $33.26 if it all falls in Tier 2.
• Time-of-Use: $39.50. Two hours a day are on-peak (9 to 11 a.m.) and six are mid-peak (11 a.m. to 5 p.m.).
• Ultra-Low Overnight: $44.07. Seven hours a day are mid-peak and the last hour, 4 to 5 p.m., is on-peak at 37.7¢.

So the cheapest plan flips. A plan that is best for night heating can be the most expensive for daytime heating. If you heat during the day, our TOU vs ULO vs Tiered comparison shows how to weigh your whole household’s use before switching.

How the Tiered threshold works in winter

From November 1 to April 30, residential Tiered customers in Ontario pay 11.2¢ for the first 1,000 kWh a month and 13.2¢ above that. In summer the threshold drops to 600 kWh. The OEB says the higher winter threshold is there so households can use more power at the lower price during the heating season.

A space heater adds to whatever your home already uses. If your household normally uses 800 kWh a month in winter, an overnight heater adding 360 kWh takes you to 1,160 kWh. The first 200 kWh of the heater’s use would be billed at 11.2¢ and the last 160 kWh at 13.2¢.

What these numbers leave out

Every figure here is the Electricity line of your bill. The OEB’s bill guide lists separate Delivery charges, such as the distribution and transmission charges and a line loss adjustment, and Regulatory charges. So a heater’s full cost on your bill can be higher than the electricity price alone.

Taxes and the Ontario Electricity Rebate also appear on your bill and change the final amount. Your own bill shows the delivery and regulatory charges that apply to you.

Two things can push the other way. If your heater has a thermostat, it switches off once the room is warm, so it will not draw full power every hour. A lower setting also uses less than the rated wattage. The label wattage gives you the most it can cost, not the typical cost.

Quebec: what Rate D means for a heater

Hydro-Québec’s Rate D charges a lower price for energy up to 40 kWh a day times the days in your billing period, and a higher price above that. According to its rate schedule effective April 1, 2026, the prices are 7.065¢ and 11.142¢ per kWh, plus a system access charge of 46.154¢ a day.

A 1,500-watt heater costs about 10.6¢ an hour in the first block and 16.7¢ above it. Eight hours a day adds 12 kWh, so in a home that already uses close to 40 kWh a day, most of the heater’s use would be billed at the higher price.

If you rely on space heaters for much of your heating, a longer-term fix may be cheaper. Our national heat pump rebate guide covers federal help with the cost of a heat pump.

Frequently asked questions

• Sources, checked November 10, 2026: Ontario Energy Board: electricity rates (TOU, ULO and Tiered prices effective November 1, 2026); Ontario Energy Board: understanding your electricity bill; Hydro-Québec: Rate D; Hydro-Québec: electricity rates effective April 1, 2026 (Rate D, article 2.5); Hydro-Québec: price changes as of April 1, 2026.
• Method: kWh = heater watts ÷ 1,000 x hours. Cost = kWh x price per kWh. Overnight example: 1,500 W, 11 p.m. to 7 a.m., 30 nights. Home office example: 1,500 W, 9 a.m. to 5 p.m., 21 weekdays, priced hour by hour against the winter TOU and ULO periods. Calculated by script and re-checked with a separate hour-by-hour calculation. All examples are hypothetical, assume full rated power and exclude delivery, regulatory charges, taxes and rebates.

Important: This guide is general information, not financial advice. Electricity prices and plan rules can change; check your own bill and your utility before you change plans. Gizly is not paid by any utility, and this page has no affiliate links. See our affiliate disclosure.