Steam Generator Sizing Guide

Choosing the right steam generator starts with measuring the steam enclosure and checking the sizing instructions for the exact generator you are considering. Room volume is an important part of the calculation, but manufacturers may account for ceiling height, materials, and installation conditions differently.

Use this guide to measure your enclosure, understand the factors that may affect sizing, and compare generator models. Always confirm the final selection using the current manufacturer specifications and installation requirements.

Why Steam Generator Sizing Matters

A generator that is too small may not produce steam as expected for the enclosure. A larger model may add cost and require different electrical service or installation planning.

The goal is to match the enclosure to a generator rated for that space and confirm that the controls, electrical service, plumbing, and installation meet the manufacturer’s requirements.

Step 1: Calculate Your Steam Room’s Cubic Footage

Measure the inside length, width, and height of the finished steam enclosure. Use feet for each measurement.

Length × width × height = cubic feet

For example, an enclosure measuring 4 feet long, 5 feet wide, and 8 feet high has a volume of 160 cubic feet:

4 × 5 × 8 = 160 cubic feet

Measure the steam enclosure itself, not the entire bathroom. If your measurements are in inches, convert each measurement to feet by dividing by 12 before multiplying.

For an enclosure made up of rectangular sections, calculate the volume of each section and add the results together. For a sloped ceiling or curved enclosure, follow the manufacturer’s measurement method or ask a qualified installer to confirm the volume.

Step 2: Check Materials and Room Conditions

The enclosure’s materials and construction may affect sizing, depending on the manufacturer’s method. Stone, glass, insulation, exterior walls, ceiling height, and other project details may be treated differently across brands and models.

Do not apply a general material multiplier unless the manufacturer specifies it for the generator you are considering. For example, Kohler’s sizing instructions for the models in its chart below state that wall material does not affect sizing under its method. Other manufacturers may account for room materials or conditions differently.

If your enclosure has a sloped ceiling, extensive glass, an exterior wall, or other nonstandard features, check the manufacturer’s instructions or ask a qualified steam-system professional to confirm the sizing.

Step 3: Apply the Manufacturer’s Sizing Method

Use the sizing chart, calculator, installation manual, or product specifications for the exact generator model. Do not apply an adjustment from one brand to another.

For example, Kohler specifies an 8-foot recommended ceiling height for the models in its chart. For each additional foot above 8 feet, Kohler instructs customers to select the next larger generator. Kohler also specifies a maximum ceiling height of 10 feet for those models. Follow the documentation for the exact model you are considering.

For Kohler systems, use the Kohler Steam Shower Generator Sizing Calculator and verify the result against the specifications and installation requirements for the exact model.

Kohler Invigoration Series Steam Generator Capacities

The following maximum steam room volumes are from Kohler’s published installation instructions. The 18 kW, 22 kW, 26 kW, and 30 kW systems use two generators, as indicated.

5 kW — Maximum room volume: 84 cubic feet

7 kW — Maximum room volume: 112 cubic feet

9 kW — Maximum room volume: 240 cubic feet

11 kW — Maximum room volume: 317 cubic feet

13 kW — Maximum room volume: 447 cubic feet

15 kW — Maximum room volume: 500 cubic feet

18 kW — Two 9 kW generators — Maximum room volume: 550 cubic feet

22 kW — Two 11 kW generators — Maximum room volume: 634 cubic feet

26 kW — Two 13 kW generators — Maximum room volume: 894 cubic feet

30 kW — Two 15 kW generators — Maximum room volume: 1,000 cubic feet

These are Kohler-specific ratings, not a general sizing chart for other brands. Confirm the current capacity, ceiling-height limits, electrical requirements, and installation details for the exact model before purchase.

Step 4: Confirm Electrical and Installation Requirements

Steam generators require appropriate electrical, plumbing, and enclosure preparation. Exact requirements vary by model and system. Before ordering, check the manufacturer’s documentation for:

• Voltage, amperage, and required circuit

• Generator location and maximum permitted distance from the enclosure

• Steam-line length and routing

• Plumbing connections

• Compatible controls, sensors, and steam head

• Enclosure waterproofing and ventilation

• Installation and future service access

Do not use a general electrical chart or distance adjustment unless the manufacturer provides it for the generator you are considering. Have electrical and plumbing work completed by qualified professionals as required by the manufacturer and local code.

Don’t Forget the Control Kit and Other Components

Some steam generators require separately purchased controls or other compatible components. Depending on the brand and system, these may include a control interface, temperature sensor, steam head, or accessories.

Check the product page and manufacturer documentation to confirm what is included and what must be purchased separately. For Kohler systems, verify that the selected controls and accessories are compatible with the exact generator model.

Quick Sizing Checklist

• Measure the inside of the steam enclosure, not the full bathroom.

• Calculate length × width × height in feet to find cubic volume.

• Check whether the manufacturer requires adjustments for ceiling height, materials, or other conditions.

• Match the result to the exact model’s rated capacity.

• Confirm electrical, plumbing, control, steam-line, and installation requirements.

• Ask the manufacturer or a qualified installer to confirm sizing for a custom enclosure.

Frequently Asked Questions

What if my steam enclosure is an unusual shape?

For an enclosure made up of rectangular sections, calculate the volume of each section and add the results together. For a sloped ceiling or curved enclosure, follow the manufacturer’s measurement method or ask a qualified installer to confirm the volume.

Does a generator’s kW rating tell me its capacity?

Not by itself. Compare the enclosure’s volume with the maximum room size and sizing instructions for the exact generator model. Different models and manufacturers may have different capacity ratings.

How far can the generator be from the steam enclosure?

The permitted distance depends on the generator and installation. Check the manufacturer’s installation instructions for the exact model, including steam-line length and routing requirements.

Can one generator serve more than one steam enclosure?

Do not assume that it can. Check the manufacturer’s documentation for the generator and control system, or ask the manufacturer or a qualified installer.

What should I do if I am unsure which generator to choose?

Confirm your measurements and compare them with the manufacturer’s current sizing information. For a custom enclosure or installation, ask the manufacturer or a qualified steam-system professional to confirm the model before purchasing.

Shop Steam Generators

Prime Regeneration offers residential steam generators and related components from established manufacturers. Review each product page for model-specific capacity, control compatibility, electrical requirements, shipping information, and warranty details.

Browse Steam Generators, shop Kohler Steam Generators, or contact Prime Regeneration with product questions.

Related Guides

• Steam Shower Installation Requirements

• Steam Shower vs. Traditional Sauna

• Sauna Heater Sizing Guide

• Sauna Installation Guide

• Sauna Buying Guide

Important Sizing Notice

This guide is for general planning and product comparison. Final generator sizing and installation must follow the current manufacturer’s specifications and instructions for the exact model and enclosure. Electrical, plumbing, waterproofing, and code requirements should be reviewed with qualified professionals.