Wood Burning Hot Tub Heater

Wood Burning Hot Tub Heater

Heat your hot tub using no electricity! This heater sits beside you, inside the hot tub.

Our house has all its electric power generated on-site, so an electrically heated spa pool was just not feasible. So Allan designed a wood-burning heater, made of stainless steel that could sit inside a cedar hot tub to heat the water.

Hot tub heater
This wood-burning hot tub heater consists of a firebox joined to a secondary burn chamber with internal tubes to provide more hot surface area. The flue is in three parts and the lower part, which is attached to the heater, has a water jacket.

The firebox is top loading and burns downwards, the flames passing into the large secondary burn chamber where it completely double burns and finally exits the chimney with NO visible smoke

The heater has been carefully designed to maximise the heat transfer from the heater to the water in the hot tub.


A small pump is used to circulate water through a filter and to move the tub water around. Our 1800 litre hot tub takes about 6 hours to heat to 37°C from cold. If the heater is used every day, it will reheat in about an hour and needs only about an armful of dry gorse. Perhaps I should say that we have a good supply of mature gorse. It much prefers dry wood and we also burn our ‘burnable’ rubbish which includes citrus skins.This is a brilliant way to have a cosy hot tub on a cold, dark night – using next to no electricity. You are very welcome to come and try it for yourselves.