Choosing the best electric sauna heater can be confusing and it can be easy to make a mistake if you’re not sure what to look for. Below are some of our frequently asked questions:

Which power rating (kw) Sauna Heater do i need?

The first thing to bear in mind when deciding which sauna heater to go for is the size of your sauna.

The internal volume of your sauna will dictate which power heater you will require, as well as whether you have space for a small wall mounted heater, or larger standalone heater. For each of our heaters the power requirement to sauna size guidelines are included within the product spec table.

This is typically as follows (but varies model to model so please check the individual product):

Model Power Output

4.5 kW

6/6.8 kW

9 kW

10.5 kW

Capacity of the sauna


5–8/9 m³

8–14 m³

10–18 m³

Use the Finnmark sauna room heater calculator to choose the right sauna heater for your sauna space.

Bear in mind that 'actual' volume and 'computational' volume of your sauna may differ. The 'actual' volume is simply length x width x height, the 'computational' volume also takes into consideration factors such as how well insulated the sauna is and whether there is a lot of glass used in the design. Saunas with a large amount of glass and/or little insulation will require a more powerful heater. Lack of insulation, such as a barrel sauna can result in as much as 50% extra computational volume. With glass, a rule of thumb is ever square metre of glass adds a cubic metre of computational volume. If you have any question regarding volume calculations, simply contact us and we'll be happy to advise.

We strongly suggest you consult a suitably qualified electrician or electrical engineer for the installation of these heaters. It is worthwhile having an initial consultation to discuss the power output of your home and whether you are able to draw the power needed for the heater, with the existing appliances in your home.

Most U.K. domestic power supplies are between 240 and 220 volts, and 60 and 100 amps. This variation depends on a number of factors and is why unless you are suitably qualified yourself, you will need to consult a qualified electrician. Also, if you already have a large load on your domestic supply, a 9 or 10.5 kW heater may trip out the supply.

The cabling within your standard ring main is 16 amps, therefore a dedicated power supply is required from your distribution board, much like an oven or electric shower. A 6.8kW sauna heater will require an approx. 31 amp dedicated supply, a 9kW sauna heater would require an approx. 41 amp dedicated supplies and the 10.5kW sauna heaters approx. 48 amps. An electrician or electrical engineer will recommend the right solution for your individual requirements.

Do I need a 3-phase or single phase power supply for an electric sauna heater?

Most homes in the UK will only have a single phase power supply and you would probably be aware if you have access to a 3-phase supply (though it is always worth asking a qualified professional).

All our heater models up to 9 kW can function on 3 phase, single phase - 1 neutral (UK) and single phase - 3 neutrals (Norway) with the use of the Narvi N2014E Power Card (see below for more information).

10.5 kW electric sauna heaters require a 3-phase power supply. The larger commercial sauna heaters will require a specialist dedicated power supply.

Do I need a power card, control unit and thermostat
for my electric sauna heater?

All our electric sauna heaters have the option to use alternative control units and power supplies with the exception of the Narvi Steam Ready. We strongly recommend using a power card supplied by the heater manufacturer, control unit and thermostat kit as it is the quickest, safest and easiest way to install the heaters on the U.K. 230v 1N system with all the necessary elements included. However, the heater is compatible with other standalone control units should you wish.

Most electric sauna heaters are built with these control units integrated. Whilst these heaters can also be sold without should you wish to use a different controller and power card, having the integrated option from the point of manufacture makes the P.S.U. and control unit cheaper to produce and therefore cheaper for you.

Should I use a wall mounted or freestanding/standalone electric sauna heater?

The answer to this question is down to personal preference. Whilst space is a factor when choosing, wall mounted heaters better serving smaller saunas, the sauna flanges allow for standalone heaters to be fitted within sauna benching.

Heaters such as the Narvi Slim can be used as both wall mounted or standalone, with the assistance of the Narvi Slim installation base. The real question that you should be asking is ‘How big a stone capacity should I have?’.

How big a stone capacity should I have for my sauna heater?

We at Finnmark believe sauna should be done in the traditional way. Following this doctrine, the Finns say that the more stones the sauna heater has, the softer and more pleasant the löyly (sauna steam/sauna atmosphere).

From our experience this is very much true, therefore, the answer to this question is: The more the better!

How many kg of sauna stones do I need for my electric sauna heater?

Each heater is different and the amount is included under the "product specification" tab on the product page.
We also have the option to buy the heater with stones where we include the required number of sauna stone boxes for your heater with a £5 per box discount when bought together.

For more information on how many sauna stones each of our sauna heaters takes, see the sauna stones product page.

Can I pour water over the stones of my electric sauna heater?

All our electric sauna heaters are designed to have water poured over them. It is not just OK for these heaters, it's actively encouraged.

These authentic sauna heaters are designed to withstand generous ladles of water on the sauna stones.
This is what creates the unbeatable löyly characteristic of all heaters.

Just make sure you have correctly arranged your sauna stones to ensure the majority of the water evaporates from the stones and minimal water reaches the element.

Why should I buy an electric sauna heater?

Once you learn more about our sauna heater brands you'll be asking "Why would I buy anything else!".

Learn more about our brands here..

Any other questions?

If you have any other questions, please do get in touch through the Contact Finnmark page.

You can also send us an email at or call us on:

+44 (0) 1768 489273 (UK North)
+44 (0) 20 8050 2895 (UK South)

Don’t delay, get in touch today!

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If you'd like to talk about your sauna plans, or simply want some free help and advice about all things sauna, drop us a message below and we'll happily help...