MS400 · 9kW Steam Generator

★★★★★ 4.9 · 128 reviews

$3,010

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Free lifetime sizing support. Call for even better contractor pricing.

The MS400 (9kW) is our best-selling residential generator for a reason: it's the right size for the typical home steam shower — up to 450 cubic feet — and Mr. Steam's AutoSteam dispersal delivers constant, true dry steam that feels like a professional spa, not a foggy sauna. It's compact (about the size of a large briefcase), needs zero clearance, and installs flush against a wall.

ModelMS400 (MS400R2401)
Power9 kW
Room sizeUp to 450 cu ft
Voltage240V · dedicated 50A circuit
Steam qualityAutoSteam, true dry steam
Tank & heaterRecyclable stainless steel
WarrantyLifetime residential (heating element)
Made inLong Island City, NY, USA

📞 Get Best Price

✓ Free expert sizing — we confirm this is right for your room before you buy

✓ Genuine Mr. Steam unit with full manufacturer warranty

✓ Wiring & install specs included for your electrician

✓ Real steam specialists on the phone 8am–10pm, 7 days

Not sure 9kW is right? Run the free sizing calculator →

Why the MS400 is our top seller

Most residential steam showers land between 200 and 450 adjusted cubic feet — which is exactly what the 9kW MS400 is built for. It heats fast, holds temperature within a few degrees, and doesn't short-cycle the way an oversized unit does.

Mr. Steam's AutoSteam dispersal chamber is the key. It maintains constant steam instead of blasts followed by cold gaps, and delivers it dry — so it lingers in the air, breathes easy, and feels hotter without the heavy, dripping muck of cheap wet-steam units.

Built to last 15–20 years

Surgical-grade stainless steel tank and heating element resist the mineral scaling that kills budget generators in a few years. Parts are available and serviceable — this is a unit you repair, not replace.

It's backed by a lifetime residential warranty on the heating element, in writing, from a manufacturer that's been making steam generators since the category existed.

Model	Mr. Steam MS400 (MS400R2401 / MS400RB1)
Power output	9 kW
Recommended room size	Up to 450 adjusted cubic feet
Electrical	240V or 208V, single phase, dedicated 50A breaker
Steam type	AutoSteam constant dispersal, true dry steam
Tank / heater material	Recyclable stainless steel
Certifications	UL / CSA listed
Clearance	Zero clearance — installs flush to wall
Warranty	Lifetime residential on heating element
Made in	Long Island City, New York, USA

Installation at a glance

Location: install the generator within 25 ft of the steam head — a heated basement, vanity cabinet, or closet all work.
Electrical: requires a dedicated 240V (or 208V), 50A circuit. Always use a licensed electrician and confirm your panel has capacity.
Water: connects to a standard cold water line. If your home water pressure is above 60 PSI, add a pressure-regulating valve to protect the unit.
Plumbing: insulated copper line from the generator to the steam head; the steam head mounts low, about 6–12 inches off the floor.
High ceilings: over 8 ft? Add a marine-grade fan near the ceiling to push heat down — ask us how.

We include full spec sheets and wiring diagrams with every order, and we'll walk your electrician through it by phone.

How do I know 9kW is the right size?

Measure your shower L × W × H, then adjust for wall material (tile ≈ +30%, natural stone ≈ double). The 9kW MS400 covers up to 450 adjusted cubic feet. Use our free calculator or call and we'll confirm it.

Can I install it myself?

The plumbing is DIY-friendly for a handy owner, but the 240V electrical must be done by a licensed electrician. We provide all specs.

Is the steam dry or wet?

Dry. The dual-tank, high-pressure design holds a 94%+ dryness fraction, so steam lingers and breathes easy instead of dripping and feeling muggy.

What's your best price?

Call us. We offer distributor and contractor pricing that's often well below the listed figure, plus occasional at-cost and scratch-and-dent units.

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