The right electric sauna heater depends mostly on the size of your sauna cabin. Measure the volume, choose the power that fits, check whether you need 230 V or 400 V and decide how you want to control it. This guide explains each step in plain words, so you can buy with confidence.
Electric or wood-fired sauna heater?
A sauna heater warms the air and a pile of stones. When you pour water on the hot stones, steam rises. In Finland this is called löyly. There are two main kinds of heater.
Electric heater
An electric heater is the most common choice for indoor saunas and many outdoor saunas. It is easy to use: switch it on, set the temperature and wait. Many models have a timer, so the sauna is warm when you want it. You do need the right power connection.
Wood-fired heater
A wood-fired heater is mainly used in outdoor saunas. You do not need a power cable, and many people love the sound and smell of a real fire. On the other hand, you need dry wood, a safe chimney and more time and attention during each session.
How much power does your electric sauna heater need?
The power of a heater is shown in kilowatts (kW). Electric sauna heaters usually range from about 3.5 to 9 kW. A heater that is too weak takes a long time to warm up and may never reach the temperature you want. A heater that is too strong uses more power than needed and can make the heat feel harsh.
A simple rule of thumb is about 1 kW for every 1 to 1.5 m³ of cabin volume. Here is how to work it out:
- Measure the inside length, width and height of the cabin in metres.
- Multiply them: length × width × height = volume in m³.
- Divide the volume by 1.5 for the low end and by 1 for the high end.
Example: a cabin of 2 m long, 1.5 m wide and 2 m high has a volume of 6 m³. That means a heater of about 4 to 6 kW.
Does your sauna have a lot of glass, such as a glass door or a glass front? Glass loses heat faster than wood, so choose a bit more power. The same goes for walls of stone or tiles. When in doubt, check the advice of the heater manufacturer, which often lists a minimum and maximum cabin volume.
230 V or 400 V?
This is an important point, because it decides whether your home installation is ready.
- 230 V: small heaters, up to about 3.6 kW, can often work on a normal single-phase connection. This suits small cabins.
- 400 V: larger heaters need a three-phase connection, also called 400 V. Not every home has this ready to use.
Check your fuse box, or ask an electrician, before you choose a heater. Sometimes it is smart to pick a slightly smaller heater that works on 230 V, as long as it still fits the volume of your cabin.
Built-in or external control unit?
Every electric sauna heater needs a way to set the temperature and the time. There are two options.
- Built-in control: the knobs or buttons are on the heater itself. This is simple and often cheaper. You do have to go into the sauna to change the settings.
- External control unit: a separate panel, often mounted outside the cabin. You can see the temperature and set a timer without opening the door. Some units can also control the light or work with an app.
An external unit is more comfortable, but it adds to the price and needs extra wiring.
Sauna stones
The stones store heat and turn water into steam. Use only stones that are made for saunas. Ordinary garden stones can crack or even burst in the heat. Place the stones loosely, so air can flow between them. Check them now and then, and replace stones that crumble or have cracks. The heater manual tells you how many kilos of stones it needs.
Safety distances and installation
A sauna heater gets very hot. Every model has its own safety distances to walls, the ceiling and the benches. You will find these in the manual. Always follow them, and fit the heater guard if one is included, so nobody can touch the hot heater by accident.
Leave the electrical connection to a certified electrician. They will check whether your installation can handle the power, place the right fuse and connect the heater and the control unit safely. This also matters for your warranty and your home insurance.
What does a sauna heater cost?
The price of a sauna heater depends mainly on the power and the type of control. A small heater with built-in control is usually the most affordable. A powerful heater with an external control unit and app costs more. Also plan for the stones, the electrician and any changes to your fuse box. On SaunaSteamer you can filter by number of persons, price, wood type and heating, and then buy directly from the retailer.
Are you still looking for a complete cabin? See the Finnish saunas on SaunaSteamer, or read our outdoor sauna buying guide if you want a sauna in the garden.
Short checklist
- Have you measured the inside volume of your cabin?
- Does the power fit the rule of about 1 kW per 1 to 1.5 m³?
- Have you added extra power for glass or stone walls?
- Do you need 230 V or 400 V, and is it available?
- Do you want built-in or external control?
- Have you ordered proper sauna stones?
- Is a certified electrician booked for the connection?
Frequently asked questions
What size sauna heater do I need?
Use about 1 kW per 1 to 1.5 m³ of cabin volume. Add a bit more if your sauna has a lot of glass.
Can I install an electric sauna heater myself?
You can place the heater yourself, but the electrical connection should always be done by a certified electrician.
How long does an electric heater take to warm up?
A Finnish sauna usually takes about 30 to 60 minutes, depending on the cabin size and the heater power.
Can I use any stones in my sauna heater?
No. Use only stones made for saunas, because normal stones can crack in the heat.
