Best Steam Generator Size for a Small Shower
Part of our Home Spa & Outdoor guides.
Steam generators are sized by the room's volume. This page covers showers of under 150 cubic feet.
Worked example
A 3x4-foot shower with an 8-foot ceiling is 96 cubic feet: the 4 kW unit's range of 95-141 cubic feet covers it. If the walls are stone or tile, size up because masonry soaks up heat.
Adjustments
- Tile, stone or marble walls: size up one step.
- Ceilings above 8 ft: size up.
- Exterior wall or large glass: size up.
- Acrylic or fiberglass enclosure: listed size is usually fine.
Requirements
A vapor-tight enclosure to the ceiling, a sloped ceiling to stop drips, a dedicated 240 V circuit, a cold-water line and a drain. Use the calculator to check your numbers.
Example calculation
A 3x3-foot neo-angle or square shower with an 8-foot ceiling: 3 x 3 x 8 = 72 cubic feet, comfortably within a 4 kW unit's range. A 3x5 stall at 8 feet is 120 cubic feet, still within range for acrylic walls. With tile, apply a 1.5x factor (180 effective) and step up to the 9 kW class.
Making a small shower steam-ready
- Glass enclosure to the ceiling, or a transom panel above the door that can be opened to vent.
- Ceiling sloped about 1-2 inches per foot so condensation runs down the walls instead of dripping.
- Vapor barrier behind walls and ceiling.
- Steam head placed about 6-12 inches above the floor, away from where you sit.
Seating
Steam is most comfortable seated. Even small showers can fit a corner bench or a fold-down seat.
Generator placement
The generator mounts outside the shower (a vanity cabinet, closet or attic within the distance allowed by the manual), with drain access for auto-drain models.
Frequently asked questions
What happens if the generator is too small?
The room never fills with steam and the unit runs continuously; it's the most common steam shower complaint.
Is a bigger generator always better?
Within reason, slightly oversizing heats faster; but it needs a bigger breaker and wire.
Is a 4 kW generator enough for a 3x3 shower?
Yes, a 3x3x8 ft shower is 72 cubic feet, within the 4 kW range.
How long does it take to steam a small shower?
Small showers fill with steam faster than large ones; a few minutes after the generator reaches temperature.
Can I use a steam shower daily?
Many people do; descale the generator per the manual.
Do small steam showers need a sloped ceiling?
Yes, to prevent condensation dripping on users.