6 Steam Generator Sizing Mistakes That Cost Homeowners Thousands

If you’re planning a steam shower, one decision matters more than almost anything else: steam generator sizing.

Not the brand.
Not the control panel.
Not even the installer.

Sizing mistakes are the number one reason steam generators fail early, perform poorly, or need expensive replacements.

The worst part?
These mistakes don’t usually show up immediately. They show up months or years later — when fixing them is far more expensive.

This guide breaks down six steam generator sizing mistakes that cost homeowners thousands, and how to avoid them from the start.

Mistake #1: Using Only Cubic Footage

Cubic footage is important — but it’s only the starting point.

Many homeowners (and even some contractors) size steam generators based only on the shower’s length, width, and height.

What this ignores is heat loss.

Materials like:

• Natural stone

• Porcelain tile

• Glass walls

• Exterior-facing walls

all absorb heat aggressively. If you size a generator using only cubic footage, it will almost always be undersized in real-world use.

Mistake #2: Ignoring Stone and Tile Adjustments

Stone looks great — but it’s one of the toughest materials for steam systems.

Marble, granite, slate, and heavy tile act like heat sinks. They pull warmth out of the steam faster than the generator can replace it.

If a generator isn’t upsized for stone:

• It runs longer cycles

• Internal components overheat

• Scale buildup accelerates

• Lifespan is reduced

Stone showers almost always require a larger generator than basic sizing charts suggest.

Mistake #3: Forgetting About Glass and Ceiling Height

Glass is another major heat-loss factor.

Large glass panels, frameless doors, and transom windows all allow heat to escape quickly. High ceilings make the problem even worse by letting steam rise and disperse.

If your shower has:

• Floor-to-ceiling glass

• Ceilings over 8 feet

• Skylights or exterior walls

your generator needs to be sized up — sometimes significantly.

Mistake #4: Sizing Too Tight “To Save Money”

This mistake seems logical, but it usually backfires.

Some homeowners choose the smallest generator that technically meets the requirements to save money upfront.

In reality, undersized generators:

• Run constantly

• Stress heating elements

• Require more maintenance

• Fail years earlier

The small upfront savings often turn into a full generator replacement, which costs far more.

Mistake #5: Not Accounting for Water Quality and Usage

Water quality and usage patterns matter more than most people realize.

If you:

• Live in a hard-water area

• Use the steam shower daily

• Share it with multiple users

your generator experiences more stress.

In these cases, upsizing isn’t just about performance — it’s about longevity and reliability.

Mistake #6: Assuming All Brands Size the Same Way

Not all steam generator brands perform the same way at the same rating.

Each manufacturer uses different:

• Heating designs

• Recovery rates

• Performance assumptions

A generator rated for 300 cubic feet from one brand may perform very differently from another.

That’s why copying a size recommendation from a forum, builder, or neighbor can be risky.

How to Size a Steam Generator Correctly

Proper sizing takes into account:

• Cubic footage

• Wall and ceiling materials

• Glass surface area

• Ceiling height

• Water quality

• Usage frequency

When in doubt, slightly oversizing is almost always safer than undersizing.

A correctly sized generator:

• Performs better

• Lasts longer

• Requires less maintenance

• Saves money over time

Final Thoughts

Steam generator sizing mistakes don’t usually fail immediately.

They fail slowly, expensively, and inconveniently.

If you’re investing in a steam shower, sizing it correctly from the start is one of the smartest decisions you can make.

Steam Generators Built for Daily Use

Modern systems like:

• Shop ThermaSol Steam Generators Collection – Opulent Recreations

• Shop Mr. Steam Steam Generators Collection – Opulent Recreations

• Shop Delta (Steamist) Steam Generators Collection – Opulent Recreations

• Shop Kohler Steam Generators Collection – Opulent Recreations

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