A hot tub is not a summer thing. It is best in January
When someone asks when to use a hot tub, they expect to hear “May to September”. Practice says otherwise. The body barely registers the difference between 37 °C in the water and 25 °C in the air. The difference between 37 °C and frost is an experience people drive to the mountains for.
Why it works better in winter
Hot water works by contrast. The bigger the gap between water and air, the stronger the sense of warmth and the more pronounced the release when you climb out. In summer a bath is pleasant. In winter it is an event.
Then there is the steam. At minus five a column of steam rises from the surface with the stars visible through it – and that is the thing people photograph and send to friends. In August there is no steam.
A practical note people do not expect: your hair freezes in the frost. Nothing happens to it, but a hat by the tub is not a silly idea.
What winter running actually costs
With a wood-fired tub the answer is simple. Heating from ten degrees takes 15 to 20 kg of hardwood, so roughly €2.50 to €3.50 per heat-up. In frost you feed it more – say a third more wood.
A tub with a stove needs no electricity at all, so it works just as well at a cottage with no supply as it does beside a house. Heating takes an hour and a half with an internal stove, around two hours with an external one.
The one thing that makes winter expensive is a missing thermal cover. Without it, more heat escapes through the water surface than through all the walls together, and heating stretches from an hour and a half to several hours. With a heated whirlpool the effect is even stronger – the cost breakdown is in What a whirlpool costs to run.
What to watch out for
Do not leave the tub full when you are not using it. Ice takes up more volume than water and expands. The composite shell is fine, but the stove and pipework are not – which is why the stove jacket is drained too before a longer break.
The path to the tub turns into an ice rink in winter. Non-slip steps or a piece of decking around the tub is not a luxury; it is what stops an accident at the moment you are walking barefoot on something wet.
The full procedure for winter running and for winterising is in Whirlpool and hot tub in winter.