Dry hardwood · barely any smoke
Dry hardwood for wood-fired hot tubs, cut to 8–10 inches so it drops straight into a tub stove. Two net bags and a couple of hours from cold for a typical tub – and no smoke in your face while you wait.
From£12net bag · free delivery across most BH postcodes
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Heat-Up Calculator
Heating water is physics, not opinion, so this works it out properly rather than guessing. Set your tub and we’ll show the wood, the time and what it costs.
1Tub volume
2Target temperature
3Time of year
4Stove type
5Which firewood
1,200 litres, 10°C to 38°C
2h 45mfrom cold
A typical 1,200 litre tub with an internal stove needs about 39 kWh to climb from 10°C to 38°C. That is roughly 13.6kg of kiln dried hardwood: a net bag and a half, so buy two.
In winter, from 4°C, allow about a fifth more wood and time. An external stove is slower again. Keep the cover on until you get in.
Show The Working
Plenty of firewood sites will tell you a hot tub takes “a few logs”. Here is the actual arithmetic, so you can check it or argue with it.
Every litre needs 4.186 kilojoules to lift it one degree. Multiply by your volume and by the temperature climb and you have the job in kilowatt hours.
litres × 4.186 × Δ°C ÷ 3600 = kWhHardwood at under 20% moisture holds roughly 4.1 kilowatt hours per kilo. Wet wood holds the same energy but spends a chunk of it boiling off its own water first.
4.1 kWh per kg of dry hardwoodNo stove is perfect. An internal stove sitting in the water gets most of it across; an external one loses more to the garden. We assume about 70%.
kWh needed ÷ (4.1 × 0.7) = kg of woodThat depends on how fast the stove can push heat into the water – roughly 14kW for an internal stove, 10kW for an external one, burning steadily.
kWh needed ÷ kW delivered = hoursThe reason this matters is that moisture is the whole ball game. A log at 40% moisture holds roughly the same raw energy as a log at 15%, but a large share of it is spent turning the water inside the log into steam before any heat reaches your tub.
That is why a tub that “takes four hours” with wood off the back of a neighbour’s hedge takes closer to two with kiln dried. Same stove, same tub, same effort – different wood.
The figures the calculator gives are a fair estimate, not a promise. Wind, an uncovered tub, a stove that needs its baffle cleaning and how attentively you feed it all move the number. Buy for the worse case and keep the spare dry.
Delivery slots up to a month ahead.
Why Dry, Specifically
Dry wood is better everywhere. For a hot tub it is close to non-negotiable, and not only for the reason you would expect.
This is the argument that matters most and gets made least. In a stove, smoke goes up a two-metre flue and away. On a hot tub you are outdoors, at flue height, downwind of your own fire for two hours. Wet wood smoulders. Dry wood barely smokes at all.
The energy that boils water out of a wet log is energy that never reaches your tub. Dry hardwood gets a typical tub to temperature in two to four hours. Damp wood can add hours to that, and on a cold night may not get there at all.
A smoking flue in a Dorset garden on a still evening travels a long way. It is the single most common reason hot tub owners get a knock at the door, and it is almost always the wood rather than the tub.
Holiday Lets & Glamping
A wood-fired tub is a brilliant listing photo and a poor guest experience if the wood is damp. Guests do not know how to nurse a bad fire, and the review says the tub never got hot.
We supply sites across Dorset through the season – campsites, glamping fields, shepherd’s huts and holiday cottages – on a schedule rather than an emergency phone call.
Keep reading
For a typical 1,200 litre tub heated from cold, budget roughly 15 to 20kg of dry hardwood – about two net bags – and two to four hours. In deep winter with water coming in at 4°C it is nearer the top of that; in August with the tub already at 16°C it is well under. Once it is up to temperature, keeping it there with the cover on costs very little, well under half a kilo an hour.
Dry hardwood. Ash, oak, beech and our seasoned mixed are all good – dense wood gives a long steady burn, which is what a heat exchanger wants. Softwood burns fast and hot and then stops, so you spend the evening feeding it, and it spits. Kiln dried is the quickest to temperature; seasoned is cheaper and perfectly capable if you are not in a rush.
Almost certainly. We cut to 8 to 10 inches, roughly 20 to 25cm, and most wood-fired tub stoves take up to about 30 to 40cm. If yours is a small integrated stove, measure the door before you order a bulk load – and ash splits down easily by hand if you need to.
You can get a fire going with them, but it is a bad evening. Wet wood spends its energy boiling off water rather than heating your tub, so it takes far longer, and it smokes heavily – which matters more here than anywhere else, because you are sitting outdoors at the same height as the flue, in your own garden, next to your neighbours.
Two to four hours for a typical tub from cold, depending on size, the water temperature you start from and whether the stove is internal or external. Internal stoves sit in the water and heat it faster. The single biggest thing you control is the wood: dry hardwood will do it in the time above, damp wood may never quite get there.
It is a different shape of cost rather than a simple win. A wood-fired tub costs you two net bags and a couple of hours each time you use it, with nothing ticking over in between. An electric tub costs less per session but holds temperature around the clock. If you use the tub every day, electric usually wins; if you use it at weekends, wood usually does.
Yes, and it is a lot of what we do in summer. Sites across Dorset take regular drops through the season, either net bags for guests to help themselves or bulk delivered and bagged on site. Multiple properties under one owner can go on a single monthly invoice.
Anything treated, painted, glued or reclaimed – fence panels, pallets, old decking, chipboard. They release genuinely nasty things at head height while you sit in the water. Also no accelerants, ever. Kindling, a firelighter and dry hardwood is all it needs.
Dry hardwood cut to fit a tub stove. Free delivery across Dorset, pay on the day.
Delivery slots up to a month ahead.
Pay the driver on delivery. No deposit. 01202 022560