Setting up an electric sauna heater

Electric is how most people heat a home sauna. Press a button, wait, get in. There is no fire to light and nothing to clean out afterwards. But a sauna heater is not something you plug in, and there are a few things worth understanding before you buy one.

Getting the size right

Heater size is measured in kW, and it comes from how much air is inside your sauna rather than how many people sit in it.

Too small and the sauna never quite gets there. You sit waiting, the stones do not hold their heat, and throwing water on them kills the temperature instead of lifting it. Too big and you cook the room before the stones are properly hot, which gives you a sauna that feels fierce and dry rather than deep and soft.

A few things push the size up. A big glass front loses heat much faster than timber. Thin solid timber walls with no insulation lose it faster again. Sitting outside through a British winter adds a little more. A sauna with a separate changing room only counts the part you actually heat.

What your electrics need to handle

A sauna heater cannot go in a plug socket or an extension lead. It is wired into its own dedicated circuit, in the same way an electric shower or an oven is.

Heaters up to around 9kW will usually run off a normal household supply, as long as your fusebox has room spare. Whether it does depends on what else is already drawing power in the house, and your electrician can tell you in about five minutes.

Above that, most heaters need a three-phase supply. That is a heavier duty connection, and most UK homes do not have one. If you are looking at a larger sauna, check this before you buy anything else. Every other job here takes hours or days, but bringing a three-phase supply into a property can take weeks or months.

Who wires it in

The final connection is a qualified electrician's job. It is a lot of power going into a small room that gets hot and wet, and it needs doing properly.

Your electrician will run the right cable for the load and the distance, fit an isolator switch outside the sauna, and put the heater on its own protected circuit, working to the instructions supplied with that specific heater.

Once the cable run is in, connecting the heater is usually a couple of hours. Most of the cost sits in getting the cable from your fusebox to the sauna, so where the sauna sits in the garden makes a real difference to the bill.

If you are near us in Leicestershire, we can arrange the electrician as part of your order for an additional fee.

Where the heater and controls go

Decide this before the sauna is built rather than after. Running a cable through a finished cabin is awkward and sometimes means taking panels back off. On models with a changing room it is far easier to do while the walls are still apart.

Most heaters sit on the wall near the door, low down, with the benches opposite. The controller usually mounts outside the hot room, though many modern heaters are controlled from your phone instead. If your sauna is at the bottom of the garden, switching it on from the kitchen is genuinely useful.

Whichever you choose, the heater needs its stated clearance from the benches and walls, and that distance comes from the heater's own instructions.

What it costs to run

Running cost comes down to the kW of the heater, how long you run it, and what you pay per unit of electricity.

Heating from cold is where the money goes. Once the sauna and its stones are up to temperature, holding it there costs a fraction of what it took to get there. This is why people who use their sauna several times a week often find it cheaper per session than people who use one occasionally.

Most home saunas cost less per session than people expect, usually somewhere between a coffee and a pint depending on size and tariff.

Mistakes worth avoiding

Buying the heater before checking the supply. If a larger sauna needs three-phase and you do not have it, you have bought something you cannot use yet.

Undersizing to save money. The price gap between one size and the next is usually small. The difference in how the sauna feels is not.

Forgetting ventilation. A heater can only do its job if air is moving through the room. You want a vent low down near the heater and another high up on the opposite side.

Leaving the cable run until last. Where the sauna sits relative to your fusebox is one of the bigger variables in the final bill, and it is much easier to think about before the base goes down.

Still not sure

Tell us which sauna you are looking at and we will tell you the heater size it needs and what fits it. We would far rather spend ten minutes getting it right with you than have you order the wrong heater.