Choosing the right steam generator size is one of the most important decisions when installing a steam room. A generator that is too small may struggle to produce enough steam, resulting in long heating times, low steam output and an uncomfortable steam room. A generator that is unnecessarily large can increase installation and operating costs.

The correct steam generator size depends on more than the length and width of the steam room. Room volume, ceiling height, wall and ceiling materials, insulation, doors, windows, ventilation and other heat-loss factors can all affect the required generator capacity.

Whether you are installing a steam room in a home, hotel, gym, spa or commercial facility in Nairobi or elsewhere in Kenya, proper sizing helps ensure reliable steam production and efficient operation.

What Is a Steam Generator?

A steam generator is an electrical or other energy-powered appliance that heats water and converts it into steam. The steam is then delivered through a steam outlet inside the steam room.

The generator’s capacity is normally expressed in kilowatts (kW). Larger generators can produce more steam and are therefore suitable for larger steam rooms or rooms with greater heat loss.

However, selecting a generator based only on room size can lead to an incorrect installation. The characteristics of the room also need to be considered.

How Do You Calculate the Right Steam Generator Size?

The first step is to calculate the approximate volume of the steam room.

Step 1: Measure the Steam Room

Measure:

Length
Width
Ceiling height

Use the following formula:

Room Volume = Length × Width × Height

For example, if a steam room measures:

Length: 2 metres
Width: 2 metres
Height: 2.4 metres

The room volume is:

2 × 2 × 2.4 = 9.6 m³

This gives you the basic room volume from which generator sizing can begin.

However, 9.6 m³ does not automatically mean that any particular kW generator will be suitable. The construction and heat-loss characteristics of the room must also be considered.

Why Room Volume Alone Is Not Enough

Two steam rooms with exactly the same dimensions can require different generator capacities.

For example, one room may have well-insulated walls and a low heat-loss ceiling, while another may have glass walls, an external wall, a high ceiling and frequent door opening.

The second room can require significantly more steam-generating capacity.

Important factors include:

1. Ceiling Height

A high ceiling increases the volume of the room.

A steam room measuring 2 × 2 metres with a 2.4-metre ceiling has a volume of 9.6 m³.

If the ceiling height increases to 3 metres, the volume becomes 12 m³.

This means ceiling height should always be included when calculating steam room volume.

2. Insulation

Good insulation helps retain heat inside the steam room.

A properly insulated steam room generally requires less energy to maintain its temperature than a poorly insulated room.

The walls, ceiling and floor should therefore be constructed with suitable materials and moisture-resistant insulation systems designed for steam-room applications.

3. Glass Walls and Doors

Glass is commonly used in modern steam rooms, but large glass surfaces can increase heat loss compared with well-insulated solid walls.

If your steam room has a large glass door, glass partition or several glass walls, this should be considered when selecting the generator.

4. Exterior Walls

A steam room located against an exterior wall can lose more heat than one surrounded by conditioned interior spaces.

The construction of the surrounding walls therefore matters when calculating generator requirements.

5. Ceiling Construction

The ceiling is particularly important in a steam room because warm, humid air rises.

A properly designed and insulated ceiling can help the room retain heat and maintain comfortable steam conditions.

6. Door Usage

A residential steam room may have relatively little door traffic.

A commercial steam room in a hotel, gym or spa may have the door opened repeatedly throughout the day.

Frequent opening allows heated air and steam to escape, potentially increasing the required generator capacity.

Steam Generator Size for Small Steam Rooms

Small residential steam rooms generally require smaller generators than large commercial installations.

For example, a compact home steam room may have a volume of only a few cubic metres, while a hotel or spa steam room can be considerably larger.

The final generator should be selected using the manufacturer’s sizing chart and the actual construction characteristics of the room.

Do not simply purchase a generator because its kW rating appears appropriate for the room’s floor area.

Steam Generator Sizing for Hotels, Gyms and Spas

Commercial steam rooms require additional consideration.

A hotel, health club, gym or spa may experience:

Higher user numbers
More frequent door opening
Longer operating periods
Greater heat loss
Larger steam rooms
Multiple users entering and leaving simultaneously

For these applications, professional steam generator sizing is particularly important.

Depending on the project, it may also be appropriate to use multiple generators rather than relying on one very large unit.

Multiple-generator systems can provide redundancy and may allow capacity to be controlled according to demand, depending on the equipment and system design.

Why Oversizing a Steam Generator Is Not Always Better

It may seem sensible to choose the largest generator available, but oversizing is not necessarily the best solution.

An excessively large generator can:

Increase initial equipment costs
Require larger electrical infrastructure
Increase installation requirements
Consume more energy when operating
Be unnecessary for the actual steam room

The objective is to select a generator with sufficient capacity for the room and its expected heat loss without unnecessarily increasing system size.

Why an Undersized Generator Causes Problems

An undersized steam generator can create several problems.

You may notice:

Steam takes too long to appear
The room struggles to reach the desired temperature
Steam production feels weak
The generator runs for long periods
Temperature drops quickly when the door opens
Steam levels become inconsistent

If a generator is constantly operating at or near maximum capacity, it may struggle to keep up with heat loss.

This is why accurate steam room generator sizing should be done before purchasing the equipment.

Electrical Supply Must Also Be Considered

Generator capacity is closely related to electrical requirements.

A higher-kW steam generator normally requires a greater electrical supply. Depending on the equipment, installation may require a suitable single-phase or three-phase electrical connection.

Before installation, the electrician should verify:

Available electrical supply
Voltage
Phase requirements
Current requirements
Cable size
Circuit protection
Isolator requirements
Earthing
Installation location

The generator manufacturer’s electrical specifications should always be followed.

Water Supply and Drainage

Steam generator installation is not only about electrical power.

The system also requires a suitable water supply and drainage arrangement.

Water quality can affect generator performance. Hard water can contribute to mineral and scale buildup inside the generator, potentially increasing maintenance requirements.

A suitable drainage system is also important for cleaning, flushing and servicing the generator.

How to Choose a Steam Generator for a Home

For a home steam room, start by measuring the internal dimensions.

Record:

Length × Width × Height = Room Volume

Then identify:

Wall construction
Insulation quality
Ceiling construction
Amount of glass
Door size
Number of exterior walls
Expected frequency of use

Provide these details to the generator supplier or installer so that the appropriate capacity can be selected.

How to Choose a Steam Generator for a Commercial Steam Room

For commercial projects, sizing should be more detailed.

A professional assessment should consider:

Steam room dimensions
Total room volume
Wall construction
Ceiling height
Insulation
Glass area
Door size and usage
Exterior walls
Expected number of users
Operating hours
Electrical supply
Water supply
Drainage
Generator location
Manufacturer’s sizing recommendations

For a large hotel, spa or gym project, it is advisable to size the generator as part of the complete steam-room design rather than selecting the equipment after construction.

Example of Steam Generator Sizing

Consider a steam room measuring:

2 m × 3 m × 2.4 m

Its volume is:

2 × 3 × 2.4 = 14.4 m³

This gives the basic room volume.

However, before selecting the generator, the installer should determine whether the room has:

Large glass surfaces
Poor or excellent insulation
A high-traffic door
Exterior walls
Unusual ceiling construction
Other conditions that increase heat loss

The final generator capacity should then be selected according to the manufacturer’s sizing requirements.

This example demonstrates why there is no universal rule that says a specific number of cubic metres always requires one particular generator size.

Common Mistakes When Selecting a Steam Generator

Choosing Based Only on Floor Area

Floor area does not tell you the total volume of the room.

A room with a high ceiling requires more capacity than one with the same floor area and a lower ceiling.

Ignoring Glass

Large glass surfaces can significantly affect heat loss.

Ignoring Insulation

Poor insulation can make a generator appear undersized even when the basic room-volume calculation looks correct.

Forgetting Electrical Requirements

A generator may be suitable from a steam-production perspective but unsuitable for the available electrical supply.

Buying the Cheapest Generator

The lowest purchase price does not necessarily represent the lowest overall cost.

Consider equipment quality, controls, spare parts, servicing, warranty and long-term operating requirements.

When Should You Consult a Steam Room Installer?

Professional assistance is recommended when:

The steam room is large
The project is commercial
The room has extensive glass
The ceiling is unusually high
The room has complex insulation
Multiple generators are being considered
A new electrical supply is required
The steam room is part of a hotel, gym or spa
You are unsure about the correct generator capacity

An experienced installer can assess the room and recommend a suitable generator while considering electrical, plumbing, ventilation and installation requirements.

Steam Generator Installation in Nairobi and Kenya

If you are planning a new steam room in Nairobi or elsewhere in Kenya, proper generator selection should be done before purchasing the equipment.

At Refitec Kenya, steam room projects can be assessed based on room dimensions, construction, generator requirements and installation conditions. Professional planning helps avoid buying a generator that is too small or unnecessarily large.

For a quotation, provide the length, width and ceiling height of the steam room together with information about glass walls, insulation and the intended use.

Final Thoughts

Choosing the right steam generator size starts with calculating the volume of the steam room, but room volume is only one part of the calculation.

Insulation, ceiling height, glass surfaces, exterior walls, door usage, room construction and electrical requirements can all influence the final generator capacity.

For a small residential steam room, accurate measurements and the manufacturer’s sizing guidelines may be sufficient. For larger hotels, spas, gyms and commercial steam rooms, professional assessment is recommended.

The goal is to select a generator that can produce enough steam to heat and maintain the room comfortably without unnecessarily oversizing the equipment.

If you are planning a steam room installation in Nairobi or Kenya, have the room measured and assessed before purchasing the steam generator. Correct sizing from the beginning can help improve performance, efficiency and reliability.