The right heater is essential to creating the perfect atmosphere in your sauna, both in terms of warmth and ambiance.

There’s nothing worse than getting in a lukewarm sauna at the end of a long day or having to wait hours for your sauna to heat up because the heater isn't powerful enough.

Along with other sauna design factors like ceiling height, bench placement, and barrel vs square sauna, the right heater will support optimal heat circulation, even heat distribution, and a comfortable experience.

Choose the right heater for your sauna with our calculator.

Top Considerations for Sauna Heater Sizing

What are the crucial factors when calculating sauna heater size?

• Room Volume and Insulation
  
  The most critical factor for the size of your heater is the total cubic volume of the sauna room (length x width x height). Additionally, insulation quality impacts how efficiently the room retains heat; saunas with large glass surfaces or low insulation require larger heaters to compensate for heat loss​
  
  Typically, you’ll need about 1 kW of heating power for every cubic meter of sauna space. However, saunas with glass, windows, or heat-retaining surfaces like brick or concrete may require more power to maintain an optimal temperature.
  
  
• Desired Temperature and Usage Style
  
  Traditional Finnish saunas are typically heated to 70–100°C (158–212°F). If you enjoy a higher-temperature experience, you may need a more powerful heater than someone who prefers lower heat.
  
  
• Heater Power Rating (kW) and Type
  
  Sauna heaters come in various power ratings to suit different room sizes, and choosing the correct wattage is essential. Electric and infrared heaters have different heating capacities and characteristics.
  
  Electric heaters are most common for their easy control over temperature and power while wood-burning heaters are preferred in traditional setups. Each type has specific sizing recommendations, with electric heaters usually offering the most precise control​.

Why Proper Sauna Heater Sizing Matters

Optimal heat distribution is one of the main reasons you should get the size of your heater correct. If the heater is too small, it may struggle to reach the desired temperature, resulting in an uneven experience where some areas are much cooler than others. An oversized heater can heat the room too quickly, leading to intense, less enjoyable heat.

Here are a few other reasons to make sure your heater is sized correctly for your sauna:

• Energy Efficiency
  
  Correct heater sizing prevents excessive energy consumption. A smaller heater running at maximum capacity is likely inefficient, using more electricity while still needing help maintaining heat. On the other hand, an oversized heater may waste energy by overheating the room, causing users to adjust settings frequently to balance comfort and temperature.​
  
  
• Longevity of the Heater
  
  Saunas with improperly sized heaters often face wear-and-tear issues faster. A heater that is too small must work harder, which can reduce its lifespan. Properly sized heaters operate within their optimal range, reducing strain and maintenance costs over time.
  
  
• Ideal Humidity
  
  Sauna heaters also affect humidity. With a properly sized heater, users can better manage the balance between heat and humidity by controlling water poured over stones without creating sudden, sharp increases in temperature. This makes it easier to maintain a comfortable and authentic sauna experience that feels neither overly dry nor oppressively humid.​

How Do I Calculate the Sauna Heater Size I Need?

Calculating the size of a sauna heater isn't just down to the cubic feet. You’ll need to factor in the amount of glass present and insulation in your calculations. 

Generally, a minimum of 4 to 6 square feet per person in a sauna is recommended to ensure sufficient space and comfort. Typically, you’ll need about 1 kW of heating power for every cubic meter of sauna space and another kW per square meter of glass or other uninsulated surface on the walls and ceiling.

Use our sauna calculator to find the right heater for your sauna.

What type of heater should I consider?

Electrical, infrared, gas, or wood-burning— the type of heater you choose will significantly impact the sauna experience.

Electric Sauna Heater

Electric heaters are easier to start up and with the right setup, can be started remotely.

Harvia

A heater should produce significant convective heat, a convective loop, and as little radiant heat as possible. Harvia heaters are designed to prioritize convective heat, creating a steady flow of warm air that circulates throughout the sauna for an even and comfortable temperature. Harvia heaters ensure a gentle, soothing löyly that feels natural by minimizing radiant heat.

HUUM

HUMM is known for its reliability and really brings a wow factor when you step into the sauna. 

• The HUUM Drop is a compact and stylish wall-mounted heater, perfect for small to medium-sized saunas. Its rounded, minimalist design provides an elegant look while maximizing space.
  
  The HUUM Drop offers a gentle, even steam, ideal for those seeking a soft, relaxing sauna experience. It has a bracket/retainer to protect the heating elements and space them apart.
  
  
• The HUUM Hive is known for its large stone capacity and powerful, lasting heat. It’s ideal for larger saunas and those who love the rich, soft steam that surrounds you.
  
  Its larger stone capacity creates a gentler, softer löyly, especially popular in Finland. This doesn’t mean it’s less hot— more that the heat is slower and more even. In a typical electric sauna, löyly feels sharp and intense, like a burst of heat hitting you all at once. Soft löyly, by contrast, feels like a warm cloud gently enveloping you, creating a smoother and more relaxing experience.
  
  
• The Huum Steel model combines modern aesthetics with practical durability. With a moderate stone capacity, it provides balanced heat that’s both dry and intense. 

Saunum

Saunum sauna heaters combine traditional sauna heat with a unique air distribution system that creates a balanced blend of hot and cool air for a more comfortable and consistent temperature. 

Saunum heaters are designed to enhance the sauna experience, improving air quality and oxygen levels for an invigorating, refreshing session. Additionally, Saunum’s integration of Himalayan salt blocks adds beneficial minerals to the air, contributing to both relaxation and respiratory wellness.

Wood-Burning Sauna Heaters

Many of us love the ritual, the sound and smells, and the tradition of wood-heated saunas. The glow of the flames, the natural scent of burning wood, and the gentle crackling sound create a calming atmosphere.

However, wood requires more work to operate the sauna (acquiring and storing wood, starting and stoking fire) and requires more cleanup and regular maintenance, like dealing with ash and debris.