Narvi
Narvi Ultra sauna heater
Narvi makes the Ultra in 3 sizes, from 10.5 to 15 kW, for saunas of 318 ft³ to 706 ft³. Slide to your room size to see which one fits, how fast it heats and what it needs from your fuse box.
Updated Oct 18, 2026
Output
10.5–15 kW
Rooms
318 ft³–706 ft³
Stones
110 lb
Sizes
3
Which size fits your sauna?
Your room's effective volume
494 ft³
Best fit: 12 kW
Work out your effective volumeEffective volume = inside volume, plus 1.2 m³ for every m² of glass, tile or stone; × 1.5 for solid log walls (Harvia's rule, used by most planners).
Sizes and specifications
| Model | Output | Room range | Stones | Heat-up | Per session |
|---|---|---|---|---|---|
| Ultra 10.5 kW | 10.5 kW | 318 ft³–530 ft³ | 110 lb | 25–35 min | $1.58 |
| Ultra 12 kW | 12 kW | 353 ft³–636 ft³ | 110 lb | 25–30 min | $1.79 |
| Ultra 15 kW | 15 kW | 494 ft³–706 ft³ | 110 lb | 20–25 min | $1.98 |
Heat-up and cost are our heat model's estimate for each size in a room at the middle of its range: indoor, insulated walls, 68 °F around the sauna, heated to 176 °F, one hour of bathing, electricity at $0.18/kWh (United States average).
Electrical connection
| Output | three-phase 400 V (per phase) | single-phase 230 V |
|---|---|---|
| 10.5 kW | 15.2 A | 45.7 A |
| 12 kW | 17.3 A | 52.2 A |
| 15 kW | 21.7 A | 65.2 A |
Current is computed from the output; fuse and cable are shown where the maker or dealer states them. A licensed electrician sizes and installs the circuit following the heater's manual and local rules.
Where to see it
Prices and availability come from the shop or maker and change; their page is what counts. Shop offers are added as retailers join.
Sources
- narvi.fi/en/product/narvi-ultra/maker · read 2026-10-18
Other heaters for the same rooms
Questions and answers
What size sauna does the Narvi Ultra heat?
Narvi rates the sizes for these rooms: Ultra 10.5 kW 318 ft³–530 ft³; Ultra 12 kW 353 ft³–636 ft³; Ultra 15 kW 494 ft³–706 ft³. Use your room's effective volume: add 1.2 m³ for every m² of glass, tile or stone, and multiply by 1.5 for solid log walls.
What fuse or breaker does the Narvi Ultra need?
It depends on the size and your supply: Ultra 10.5 kW: 3~ 400 V: 15.2 A, 1~ 230 V: 45.7 A; Ultra 12 kW: 3~ 400 V: 17.3 A, 1~ 230 V: 52.2 A; Ultra 15 kW: 3~ 400 V: 21.7 A, 1~ 230 V: 65.2 A. A licensed electrician sizes the circuit from the heater's manual and local rules.
How long does the Narvi Ultra take to heat up?
In a well-insulated indoor room at the middle of each size's range, our heat model gives: Ultra 10.5 kW 25–35 min; Ultra 12 kW 25–30 min; Ultra 15 kW 20–25 min to reach 176 °F. Outdoor saunas, glass and cold weather take longer.
How many stones does the Narvi Ultra take?
As stated by Narvi: Ultra 10.5 kW 110 lb; Ultra 12 kW 110 lb; Ultra 15 kW 110 lb. Use the stone size the manual specifies and re-stack the stones at least once a year, replacing crumbled ones.