15kW+ Sauna Heaters

What "15kW+" Actually Means

This is the top of the wattage ladder — the heaters built for rooms most residential units can't touch. Where a 12kW heater tops out around 4–6 people, the 15kW-and-up class is sized for large home saunas and light-commercial rooms: gyms, spas, clubs, multi-tier benches, high-traffic installs where the heater has to recover fast between sessions. We're talking roughly 600 to 1,200+ cubic feet, depending on the model and how much glass the room has.

Two things change once you cross into this tier. First, the electrical gets serious — these draw 60+ amps single-phase, and several offer three-phase wiring for commercial buildings. This is not a circuit you wire casually. Second, the heaters get bigger and heavier, with more stone mass to hold the heat a large room demands. Almost everything here is floor-standing. If you're outfitting a real commercial space or a large multi-person home sauna, this is the page. If your room is under ~500 cu ft, step down to the 10.5kW class — oversizing a heater wastes power and overheats a small room.

The 15kW+ Heaters We Carry

Four product families cover this tier, spanning Harvia, HUUM, and Saunum. They differ on stone mass, max temperature, controls, and — importantly at this size — whether they offer three-phase power. Here's how they line up.

Harvia Club Series Stainless — the commercial workhorse

The Harvia Club Series is the purpose-built commercial heater here, offered in 10.5kW, 12kW, and 15kW. The 15kW stainless model covers roughly 600–989 cu ft and holds about 132 lbs of stones, capped at 194°F. What sets it apart at this size: it comes in both 240V single-phase (home use) and 208V three-phase versions, so it drops into commercial buildings on three-phase service without a workaround. Floor-standing, stainless, built for daily heavy use. This is Harvia's reliability — the "comfortable sweatpants" of the category — scaled up for a club or spa. It pairs with Harvia's Xenio controllers for digital and WiFi control.

Harvia Virta Pro HL160E (16 kW) — the floor-standing big-room heater

The Virta Pro is the commercial-grade sibling of the residential Virta line. At 16kW it covers a large 354–918 cu ft range, holds about 200 lbs of stones — more thermal mass than the Club — and runs on 240V with external controls, capped at 194°F. The heavier stone load means richer, more sustained löyly across a big room and slower cooldown between sessions. A strong pick for a large home build or a commercial room where you want Harvia reliability with more stone mass than the Club carries.

HUUM HIVE Electric — the most stone mass in the industry

The HUUM HIVE comes in 12kW, 15kW, and 18kW, and it's the design-and-steam choice at this size. The 15kW covers about 539–1,060 cu ft; the 18kW reaches up to 1,236 cu ft — the largest room any single heater on this page handles. The HIVE holds a staggering 595 lbs of stones, the most in the industry, and hits 230°F, the highest max temp we carry. That combination is what people mean when they describe HUUM steam as "like a warm misty hug" — massive stone mass plus high heat makes a softer, more enveloping löyly. HUUM controllers (the UKU series) are sold separately. If the sauna is a centerpiece and you want the best steam at the biggest scale, this is it.

Saunum Air L Package — even heat, top to bottom

The Saunum Air L package takes a different angle: it has a built-in climate equalizer that circulates air to flatten the temperature difference between your head and your feet — the classic complaint that "your face gets blasted while your feet never warm up." It comes as a complete package (heater, digital WiFi controller, and stones) in 9.8kW, 13kW, and 15.2kW. The 15.2kW covers roughly 459–741 cu ft, holds ~256 lbs of stones in the package configuration, runs on 240V, and reaches 212°F. It also has aromatherapy and Himalayan-salt dispensers built in. Best for a large room where even, comfortable heat distribution matters as much as raw output.

How to Choose Among Them

The quick decision tree at this size: pick the Harvia Club if you need a true commercial heater with a three-phase option and proven reliability. Pick the Virta Pro for more stone mass than the Club in a big-room Harvia. Pick the HUUM HIVE for the biggest rooms, the most stone mass (595 lbs), the highest heat (230°F), and the best steam. Pick the Saunum Air L if even top-to-bottom heat distribution and a complete WiFi package matter to you. The biggest practical fork is electrical: if your building is on three-phase service, the Harvia Club's 208V/3PH version is the cleanest fit. See the whole range — including neighboring wattages — in our electric sauna heater collection.

Electrical Requirements for 15kW+ Heaters

This is where the 15kW+ class genuinely differs from the rest of the lineup. These are heavy circuits — read this section carefully, and bring it to a licensed electrician before you buy. Rough single-phase reference figures, by wattage on 240V:

• 15kW @ 240V single-phase: ~62.5 amps at full load → typically an 80A dedicated breaker (code sizes to 125% of continuous load), commonly on 4 AWG copper
• 16kW @ 240V single-phase: ~66.7 amps → typically an 80A breaker, 4 AWG copper
• 18kW @ 240V single-phase (HUUM HIVE): ~75 amps → typically a 90–100A breaker, heavier gauge again

Three-phase changes the math. The Harvia Club 15kW on 208V three-phase splits the load across three legs, drawing roughly 42 amps per leg instead of 62+ on a single-phase circuit — which is exactly why commercial buildings run three-phase service for loads this size. Three-phase usually means a smaller breaker and lighter wire per leg, but it requires three-phase power at the panel, which most homes don't have. That's a key reason the Club ships in both single- and three-phase versions.

Always consult a licensed electrician before any electrical work. Electrical requirements vary by local code and jurisdiction, and these numbers are general reference only — not a substitute for a professional assessment of your specific installation. At this amperage you're often looking at a subpanel, and many jurisdictions require a permit for hardwired 240V/three-phase work. Our guide to sauna electrical requirements covers amperage, wire gauge, and rough-in — but your electrician makes the call for your building. Never treat a 15kW+ heater as plug-and-play; it is not.

What Room Size Does 15kW+ Actually Fit?

Ratings vary by model, but the 15kW+ class broadly covers large rooms from about 600 cu ft up past 1,200 cu ft. In practice:

• 600–740 cu ft: large multi-person home saunas; the Harvia Club 15kW and Saunum Air L 15.2kW land here
• 740–1,060 cu ft: light-commercial rooms; the Virta Pro 16kW and HUUM HIVE 15kW cover this band
• 1,060–1,236 cu ft: the upper edge — the HUUM HIVE 18kW is the single heater that reaches the largest commercial rooms here

The standard glass derate matters more at this scale, not less. A glass front wall radiates heat far faster than insulated wood, so subtract roughly 15% of effective volume for a glass door or partial-glass front — and commercial rooms tend to have a lot of glass. A 900 cu ft glass-heavy room behaves like a ~1,035 cu ft insulated one, which can push you from a 15kW to a 16–18kW unit. For very large or very high-traffic rooms, some commercial designs use two heaters rather than one oversized unit; that's a conversation worth having before you wire anything.

Packages, Controllers, and Stones

At this size the controller and stone count are not afterthoughts. The Saunum Air L ships as a complete package — heater, digital WiFi controller, and stones in one matched set. The Harvia Club pairs with Xenio digital/WiFi controllers, and Harvia also offers matched bundles in our Harvia packages collection. HUUM's UKU controllers are sold separately, so budget for one with a HIVE. If app-based preheat and scheduling matter for a commercial space you're not always standing in, every app-capable model lives in our WiFi-controlled heater collection.

On stones: at 132 to 595 lbs depending on model, the stone load is the thermal engine of a big room — fill the basket to spec, because under-filling a commercial heater kills its ability to hold heat between sessions. Always use proper olivine diabase sauna rocks, never landscaping stone, which can crack, crumble, or pop dangerously at sauna temperatures. If you're not sure which heater, phase, or stone setup fits your room, that's exactly the call we're here for — message us with your room dimensions, glass area, and panel type, and we'll size it with you before you commit to the electrical.