How Much Electricity Does a Sauna Use, and What Does That Cost Here?
Last updated: By The SaunaIndex Bench
The kilowatt hours are easy and almost nobody gets those wrong. What decides the bill in Ontario is which rate plan you are on and what hour you switch the thing on, and that varies by a factor of ten on the same kilowatt hour. So this calculator prices your usage on every published plan at once rather than asking you to pick one.
The same sauna, priced on every published Ontario rate
Electricity used
6 kWh a session
The same 1248 kWh a year costs $48.67 on Ultra-Low Overnight and $487.97 on Ultra-Low Overnight on-peak. That is a $439.30 difference a year for running the same sauna at a different hour, and it costs nothing to change.
| Rate plan | Session | Month | Year |
|---|---|---|---|
| Tiered Tier 112¢/kWh | $0.72 | $12.48 | $149.76 |
| Time-of-Use off-peak9.8¢/kWh | $0.59 | $10.19 | $122.30 |
| Time-of-Use mid-peak15.7¢/kWh | $0.94 | $16.33 | $195.94 |
| Time-of-Use on-peak20.3¢/kWh | $1.22 | $21.11 | $253.34 |
| Tiered Tier 214.2¢/kWh | $0.85 | $14.77 | $177.22 |
| Ultra-Low Overnight3.9¢/kWh | $0.23 | $4.06 | $48.67 |
| Ultra-Low Overnight on-peak39.1¢/kWh | $2.35 | $40.66 | $487.97 |
This model, checked against a published figure
Method
Why the rate plan is the whole answer
A sauna is a big, flexible, occasional load, which is the exact shape an overnight rate rewards.
Start with the arithmetic, which is not complicated. A heater's rating is kilowatts, an hour of it is kilowatt hours, and the rest is multiplication. Six kilowatts for an hour is six kilowatt hours. Four of those a week is 24 a week, 104 a month and 1,248 a year. Nothing about that changes with insulation, with the season or with who is sitting in the room, because the element either draws its rating or it does not.
What changes enormously is the price of each of those units. The Ontario Energy Board publishes Ultra-Low Overnight at 3.9 cents a kilowatt hour for the hours between eleven at night and seven in the morning, and on that same plan a weekday afternoon costs 39.1 cents. That is not a rounding difference, it is exactly ten times, and it turns the identical 1,248 kilowatt hours into $48.67 or $487.97. The middle of the range is where most households sit: Tiered Tier 1 at 12.0 cents gives $149.76 a year and Time-of-Use off-peak at 9.8 gives $122.30. Anyone who tells you a sauna costs a specific amount a year to run has quietly picked one of those seven numbers for you.
The reason this matters more for a sauna than for most appliances is that a sauna is the rare large load whose timing is entirely up to you. A fridge runs when it runs. A sauna runs when you decide to heat it, and moving that decision to after eleven at night on the right plan cuts the bill by ninety percent without changing anything about the room, the heater or how long you sit in it. That single choice outweighs every efficiency decision available at the build stage, and it is free. It is also the reason this page shows a table rather than a number: the number you want is the one next to the plan you are actually on, and the number worth looking at is the one two rows below it.
Sources
Sources
- Ontario Energy Board, Regulated Price Plan, prices set for November 1, 2025 - every rate in the table, read off the OEB's own Current prices heading and labelled with the date the OEB gives it.
- Indoor sauna cost guide - the published Toronto worked example this calculator checks its own model against, from RenoHouse.
Frequently asked questions
How much electricity does a sauna use?
- A 6 kW heater run for an hour uses 6 kWh, and that is the whole calculation. Four one-hour sessions a week is 24 kWh a week, 104 kWh a month and 1,248 kWh a year. For scale, that annual figure is roughly what a modern fridge uses, so a home sauna at ordinary usage is a noticeable line on a bill rather than a frightening one. What varies is not the kilowatt hours, it is what you pay for each of them.
What does a sauna cost to run in Ontario?
- For that same 1,248 kWh a year, anywhere from $48.67 to $487.97 depending only on when you switch it on. Ultra-Low Overnight is 3.9 cents a kilowatt hour and the on-peak rate on that same plan is 39.1, a spread of exactly ten times. Tiered Tier 1 at 12.0 cents puts the year at $149.76 and Time-of-Use off-peak at 9.8 cents puts it at $122.30. These are the Ontario Energy Board's own published rates, and they are the energy line only.
Why does the plan matter more than the heater?
- Because the price of a kilowatt hour in Ontario varies by a factor of ten and heater sizes do not vary by anything like that. Moving from a 6 kW heater to a 4.5 kW one cuts the bill by a quarter and costs you a room that heats less well. Moving a session from a weekday afternoon to after eleven at night on the Ultra-Low Overnight plan cuts it by ninety percent and costs you nothing at all. A sauna is a large, flexible, occasional load, which is exactly the shape of load an overnight rate is designed for.
Does this include the pre-heat?
- Yes, if you include it in the minutes you enter, and you should. The heater draws its full rated output hardest while it is bringing the room and the stones up, which is the first 30 to 45 minutes. Enter the total time the heater is switched on, not the time you spend sitting in it, or the answer will be well under what your bill shows.
How accurate is the full-output assumption?
- It is the ceiling rather than the average, because elements cycle once the room reaches temperature, and the page says so rather than hiding it. It is also checked rather than asserted: a Toronto contractor publishes about $5 a week for a 9 kW heater over four one-hour sessions at roughly 13 cents a kilowatt hour. Put the same assumptions through this calculator and it gives 36 kWh and $4.68, just under the published figure. A model that lands within a few percent of somebody else's independently published arithmetic is a model worth using.
What is not in these figures?
- Three things, all of which push the real number up. Delivery charges and regulatory charges are a separate part of an Ontario bill and are not in the OEB energy rate. Thirteen percent HST sits on top of the whole bill. And the Ontario Electricity Rebate comes off it, which pushes the other way. The figures here are the energy line, which is the part a sauna actually changes, and the part you can act on by moving when you use it.
Next
Where this number comes from
The one input that decides everything here is the heater rating. If you do not have one yet, size it from the room first, then come back with the number.