Buyer's Guide
How to size a sauna heater (and why tower heaters make better steam)
Heater size decides if a sauna reaches protocol heat or plateaus lukewarm. We match kilowatts to room volume, then cover stone mass for löyly and the controller.
By Adam Bognar, Editor
Size a sauna heater at about 1 kW per 45 cubic feet of room volume, then weigh its stone mass and control system. The heater decides whether a session reaches the temperature the research describes, so we worked that rule into a table of room sizes. Start by sizing your room below.
Try it with your room
What size heater does your sauna need?
Room volume
336 ft³
Recommended heater
7–9 kW
From our reviews, that points at Harvia Cilindro PC80E (8 kW) or Harvia KIP80W (8 kW).
Rule of thumb: ~1 kW per 45 ft³ of room volume. Always check the heater's own room-size rating and have a licensed electrician confirm the circuit. A 9 kW heater typically needs a 240V/50A non-GFI breaker.
Match the heater's kilowatts to your room's volume
Our rule of thumb is about 1 kW per 45 cubic feet of room volume. Add roughly 25% for a glass door or uninsulated outdoor walls, and more in a cold climate. A heater that's too small won't hold protocol heat through a full session. Oversizing wastes energy, and you'll spend more on the circuit too.
| Room (ft, W × D × H) | Volume (cu ft) | Base heater | With a glass door or outdoor walls (+25%) |
|---|---|---|---|
| 5 × 5 × 7 | 175 | 3.9 kW, so a 4.5 kW unit | 4.9 kW, so a 6 kW unit |
| 6 × 5 × 7 | 210 | 4.7 kW, so a 4.5 to 6 kW unit | 5.8 kW, so a 6 kW unit |
| 6 × 6 × 7 | 252 | 5.6 kW, so a 6 kW unit | 7.0 kW, so an 8 kW unit |
| 8 × 6 × 7 | 336 | 7.5 kW, so an 8 kW unit | 9.3 kW, so a 9 kW unit |
| 8 × 8 × 7 | 448 | 10.0 kW, so a 10.5 kW unit | 12.4 kW, so a 12 kW unit |
| 10 × 8 × 7 | 560 | 12.4 kW, so a 12 kW unit | 15.6 kW, so a 15 kW or larger unit |
We worked these figures from the rule of thumb in this guide, and a cold climate pushes them higher again. Always check the heater's own room-size rating, and confirm the circuit it needs before the electrician quotes.
Where to buy
HUUM CLIFF 9 9kW Electric Sauna Heater. HUUM photography.
See the specifications and priceStone mass makes the steam
Stone mass is the underrated spec. A compact wall heater holds around 50 lbs of stones, while tower heaters like the Harvia Cilindro or HUUM HIVE hold 200+ lbs. A bigger load of hot stone stores more heat for each ladle of water, and that gives you longer-lasting heat and better löyly.
Where to buy
Harvia Heaters & Stoves
Harvia Cilindro PC80E 8kW Electric Sauna Heater
“Stone packed around the elements lets this tower make about as much steam as a home electric heater can.”
Common questions
- What size sauna heater do I need?
- You'll need roughly 1 kW of sauna heater per 45 cubic feet of room volume, plus about 25% more for glass doors or uninsulated outdoor walls. A typical 8×6×7 ft room (~336 cu ft) suits an 8 kW heater. Always check the heater's own room-size rating.
- Are expensive tower heaters worth it?
- Yes. Tower heaters are worth it if you care about löyly. Their large stone mass stores more heat, so they give steamier, longer-lasting heat than a small wall heater and hold temperature better through repeated water throws. A wall unit saves money for a dry, quick heat-up.
Sources
- 1.Association Between Sauna Bathing and Fatal Cardiovascular and All-Cause Mortality Events. JAMA Internal Medicine, 2015.
- 2.NFPA 70: National Electrical Code (NEC). National Fire Protection Association, 2023.
- 3.Electric Power Monthly: Average Price of Electricity to Ultimate Customers. U.S. Energy Information Administration, 2025.
We review from makers’ documentation, owner reports and published research. How we choose products and write reviews.
