Which needs more electricity, a sauna or a steam room?

In most domestic-sized rooms the steam generator is the bigger connected load, because the steam sizing chart multiplies the room volume before it picks a unit. A tiled enclosure is multiplied by 1.35 and a stone one by 2.0, so a 210 cubic foot room is sized as 283.5 or 420 cubic feet, and lands on a 10 kW generator. The same 210 cubic feet as a sauna calls for roughly 4.2 to 4.5 kW. Put your own room in the calculator, because the answer flips once a sauna carries a lot of glass.

Why does glass change the sauna answer so much?

Harvia's manual treats glass as extra volume rather than as a surface: every square metre of glass, brick, tile or concrete adds 1.2 cubic metres to the figure you size the heater against. Twenty square feet of glass in a 6 by 5 by 7 room adds about 79 cubic feet, which is more than a third of the room again, and it moves that room from a 4.5 kW heater to a 7.5 kW one. The manual's own worked example says a 10 cubic metre room with a glass door is equivalent to about 12 cubic metres.

Does a steam room need a different room than a sauna?

Yes, and it is the part that costs money. A sauna is a dry, lined timber room over a floor that can take a splash. A steam enclosure is a sealed, sloped, fully waterproofed wet room with a drain and a vapour-tight ceiling, and the steam sizing guide asks how many exterior walls it has because they pull heat out of it. That is why the multipliers exist at all, and why an exterior-wall enclosure is sized 10 to 20 percent larger.

What does the cost per session in this tool include?

The energy line only, at the Ontario Energy Board rate you pick, and it assumes the unit draws its full rated output for the whole time it is on. That is the ceiling rather than the average, because elements cycle once the room is up to temperature. Delivery charges, regulatory charges and 13 percent HST sit on top of the energy line, and none of them are in this figure.

Can one room be plumbed for both?

Not as one enclosure. The two rooms want opposite things from their construction: a sauna wants a vapour barrier holding dry heat in and timber that stays dry, a steam room wants a waterproof membrane, a slope and a drain. Combination units exist as factory-built cabins, but converting a single site-built room to do both is not a thing this calculator sizes, and any company quoting it should be asked which of the two builds it is actually delivering.

Where do the sizing rules in this calculator come from?

Three published sources, named on the page and linked below. The sauna heater band comes from a Canadian retailer's chart of one kilowatt per 50 cubic feet and from Harvia's own data sheet, which rates a 4.5 kW heater to 6.0 cubic metres. Those two disagree slightly, so the tool shows the band they span rather than averaging them. The glass allowance and the log-wall multiplier come from Harvia's heater manual, and every steam figure comes from Steamist's sizing guide.

Sauna or Steam Room: What Would Each One Draw in Your Room?

Last updated: September 13, 2026By The SaunaIndex Bench

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A traditional sauna and a steam room are not two versions of one thing. They are sized by different published rules, they need different rooms around them, and in the same space they land on different equipment. Put the room in once below and the calculator sizes it both ways, then prices a session on each at whichever Ontario electricity rate you are actually on.

Size and cost the same room both ways

Room length (ft)

Room width (ft)

Ceiling height (ft)

Glass in the sauna (sq ft) - door, window or glass front

Minutes the unit is on, pre-heat included

Steam enclosure lining

Exterior walls in the enclosure

Your electricity price

In this room the sauna is the smaller electrical load: a 6 kW heater against a 10 kW steam generator.

Traditional sauna

6 kW heater

Rule calls for: 4.83 to 5.13 kW
Volume after the glass allowance: 241.5 cu ft (6.84 m³)
Energy, full output: 4.83 to 5.13 kWh
Running temperature: 158–194°F
Pre-heat: 30–45 min

$0.58 to $0.62 per session, energy only

Steam room

10 kW generator

Sizing multiplier: ×1.485
Adjusted volume: 311.9 cu ft (8.83 m³)
Energy, full output: 10.00 kWh
Running temperature: not published by the sizing source
Pre-heat: not published by the sizing source

$1.20 per session, energy only

Room as measured: 210 cu ft (5.95 m³), run for 1 h at 12¢/kWh. Energy figures assume the unit draws its full rated output for the whole time it is on, which is the ceiling rather than the average, and they are the energy line only: delivery, regulatory charges and 13% HST sit on top.

Method

How the two sides are worked out

Two published sizing methods, applied exactly as their authors wrote them, with nothing reconciled between them.

The sauna side starts with the room volume and then applies Harvia's allowance for surfaces that store heat instead of reflecting it. The manual says that for every square metre of uninsulated wall or ceiling you should calculate an additional 1.2 cubic metres of volume, and it gives the worked case: a 10 cubic metre room with a glass door is equivalent to about 12. That adjusted volume then meets two heater rules that do not quite agree. A Canadian retailer publishes one kilowatt per 50 cubic feet. Harvia's data sheet rates its 4.5 kW heater to a room of 2.8 to 6.0 cubic metres, which works out at 47.1 cubic feet per kilowatt at the top end. Rather than split the difference, which would invent a figure neither source published, the tool shows the band the two rules span and then names the smallest heater on the published Canadian ladder that clears the top of it.

The steam side does not work that way at all. Steamist's guide never adjusts for glass; it adjusts for what the enclosure is lined with, how many of its walls face outside, and how high the ceiling is. Tile or glass block multiplies the volume by 1.35, natural stone or marble by 2.0, one exterior wall by 1.1 and two by 1.2, a nine foot ceiling by 1.15 and a ten foot one by 1.3. The adjusted figure is then read straight off the manufacturer's chart, which runs from 7.5 kW at 250 cubic feet up to 15 kW at 675. Past 675 the chart stops, and so does this tool, because extrapolating a manufacturer's table past its last row is guessing with a citation attached.

The cost line is deliberately the simplest part and the most clearly labelled. It is rated output multiplied by the time the unit is on, multiplied by the Ontario Energy Board rate you select. Real elements cycle once the room reaches temperature, so this is a ceiling rather than an average, and it is the energy portion of a bill only: delivery, regulatory charges and 13% HST are all on top of it. What the calculator cannot know is the part a quote covers instead, which is the room. A sauna needs framing, foil vapour barrier, cedar and a 240V circuit. A steam enclosure needs a waterproof membrane, a slope, a drain and a vapour-tight ceiling. Those are where the difference in the two projects actually shows up.

Sources

Where these numbers came from

Northern Lights Cedar Saunas (Canada), sauna heater sizing chart - one kilowatt per 50 cubic feet, and the published ladder of heater sizes.
Harvia JH45B electric heater data sheet - 4.5 kW rated to a sauna room of 2.8 to 6.0 cubic metres.
Harvia 20 Pro heater instruction manual - the 1.2 cubic metre allowance per square metre of uninsulated surface.
Steamist steam generator sizing guide - every steam multiplier and the generator chart.
Ontario Energy Board, Regulated Price Plan, prices set for November 1, 2025 - every electricity price offered in the rate menu.

Read off the pages they cite in August 2026. Where the two heater rules disagreed, SaunaIndex widened the range rather than picking one.

Frequently asked questions

Which needs more electricity, a sauna or a steam room?: In most domestic-sized rooms the steam generator is the bigger connected load, because the steam sizing chart multiplies the room volume before it picks a unit. A tiled enclosure is multiplied by 1.35 and a stone one by 2.0, so a 210 cubic foot room is sized as 283.5 or 420 cubic feet, and lands on a 10 kW generator. The same 210 cubic feet as a sauna calls for roughly 4.2 to 4.5 kW. Put your own room in the calculator, because the answer flips once a sauna carries a lot of glass.
Why does glass change the sauna answer so much?: Harvia's manual treats glass as extra volume rather than as a surface: every square metre of glass, brick, tile or concrete adds 1.2 cubic metres to the figure you size the heater against. Twenty square feet of glass in a 6 by 5 by 7 room adds about 79 cubic feet, which is more than a third of the room again, and it moves that room from a 4.5 kW heater to a 7.5 kW one. The manual's own worked example says a 10 cubic metre room with a glass door is equivalent to about 12 cubic metres.
Does a steam room need a different room than a sauna?: Yes, and it is the part that costs money. A sauna is a dry, lined timber room over a floor that can take a splash. A steam enclosure is a sealed, sloped, fully waterproofed wet room with a drain and a vapour-tight ceiling, and the steam sizing guide asks how many exterior walls it has because they pull heat out of it. That is why the multipliers exist at all, and why an exterior-wall enclosure is sized 10 to 20 percent larger.
What does the cost per session in this tool include?: The energy line only, at the Ontario Energy Board rate you pick, and it assumes the unit draws its full rated output for the whole time it is on. That is the ceiling rather than the average, because elements cycle once the room is up to temperature. Delivery charges, regulatory charges and 13 percent HST sit on top of the energy line, and none of them are in this figure.
Can one room be plumbed for both?: Not as one enclosure. The two rooms want opposite things from their construction: a sauna wants a vapour barrier holding dry heat in and timber that stays dry, a steam room wants a waterproof membrane, a slope and a drain. Combination units exist as factory-built cabins, but converting a single site-built room to do both is not a thing this calculator sizes, and any company quoting it should be asked which of the two builds it is actually delivering.
Where do the sizing rules in this calculator come from?: Three published sources, named on the page and linked below. The sauna heater band comes from a Canadian retailer's chart of one kilowatt per 50 cubic feet and from Harvia's own data sheet, which rates a 4.5 kW heater to 6.0 cubic metres. Those two disagree slightly, so the tool shows the band they span rather than averaging them. The glass allowance and the log-wall multiplier come from Harvia's heater manual, and every steam figure comes from Steamist's sizing guide.

Ready to price the actual build?

The calculator sizes equipment. What it cannot size is the room around it, and that is most of a quote. SaunaIndex lists 38 sauna companies across the Greater Toronto Area, each with a quote request on its profile rather than a lead broker's form.

Browse sauna companies in the GTA Read what each build needs from the house Indoor sauna cost guide