Why moisture content is the number that matters most

Whatever you feed your stove, the single biggest factor in how well it burns is how much water is locked inside the wood. Freshly felled timber can be 50% water by weight or more. Every kilogram of that water has to be boiled off and driven up the chimney before the wood can give you any real heat, and doing that steals energy that should be warming your living room.

The practical target for a wood burning stove is a moisture content below 20%, with many experienced stove users preferring somewhere around 15–18%. At that level, logs light readily, burn with a steady flame and leave a crisp, grey-white ash rather than sticky black tar. Above 25%, you get hissing, spitting, smoky fires, poor heat output and a flue that soots up far more quickly. A cheap moisture meter, pressed into a freshly split face rather than the end grain, costs very little and takes the guesswork out of the whole business.

Seasoned logs: the traditional route

Seasoning is simply letting nature do the drying. Logs are split, stacked somewhere with good airflow and left for anything from nine months to two years, depending on species, split size and the weather. Softwoods such as pine and spruce dry faster; dense hardwoods like oak, ash and beech take longer but reward you with a longer, slower burn and more heat per log once they are ready.

Well-seasoned logs are a pleasure to use when they are genuinely dry. They are usually the cheaper option per cubic metre, they feel natural and they suit anyone with space to store a decent quantity. The catch is that "seasoned" is a word with no legal definition. A builder's bag advertised as seasoned may still be sitting at 28% moisture if it was split late and stacked in a damp corner. Bark that peels away easily, a hollow sound when two logs are knocked together and visible cracks radiating from the ends are all good signs, but only a meter gives you a definite answer.

If you buy in spring and stack it properly, you can finish the job yourself. Raise the stack off the ground on pallets, keep it under a breathable cover that protects the top while letting the sides breathe, and leave a gap between the stack and any wall. Never tarp the whole thing down tightly — trapped damp simply moves back into the wood.

Kiln dried firewood: consistency you can rely on

Kiln dried logs are heated in a large drying chamber until moisture content drops, typically to somewhere between 10% and 20%, and often to around 15%. The result is a reliably dry product that lights easily, burns hot and clean, and behaves predictably from the first log to the last. For anyone who has struggled with a sulking, smoky fire on a cold evening, that reliability is worth a great deal.

Because the water has already been driven out, kiln dried logs give noticeably more usable heat per log. You will generally get through fewer of them to reach the same room temperature, and you will produce less creosote in the flue, which means less sweeping and a lower risk of a chimney fire. They also store more compactly and can be brought straight indoors without the long drying period.

The trade-offs are cost and provenance. Kiln drying uses energy, so the price per bag or crate is higher, and the fuel used in the kiln affects the overall environmental picture. Look for suppliers who dry with waste wood or biomass, and buy in bulk where you can to soften the per-log price.

Cost, storage and how the two compare in practice

• Upfront price: seasoned logs are usually cheaper per cubic metre, but you may pay again in wasted heat if they are not properly dry.
• Heat per log: kiln dried generally wins, so the true cost per kilowatt hour is closer than the headline prices suggest.
• Storage: seasoned wood needs months of covered, ventilated space; kiln dried can be used almost immediately and kept in a log store or basket.
• Consistency: kiln dried is uniform; seasoned varies from bag to bag and even within a bag.
• Flue maintenance: drier wood means less soot and tar, so fewer sweeps and less chimney wear.
• Convenience: kiln dried suits small urban gardens, flats with a log store and anyone short on drying space.

Getting the best from either fuel

Whichever you choose, a few habits make a real difference. Store logs indoors only a day or two ahead of burning, and keep a small stock near the stove so it is at room temperature when it goes on. Build the fire with kindling and a couple of small splits, get the flue warm quickly, then add larger logs once the bed of embers is established. Burn hot and bright rather than slumbering — a stove left to smoulder on a low air setting is the fastest way to line your chimney with tar.

Have the flue swept at least once a year, more often if you burn a lot or use fuel of uncertain quality. And if you are buying seasoned logs, invest in a moisture meter and check a few split pieces from every load. Sending back a wet delivery is far easier than dealing with a blocked flue in January.

Many households settle on a sensible middle ground: a bulk load of seasoned hardwood bought early in the year and stacked to finish drying, topped up with a few crates of kiln dried logs for damp evenings, busy weeks and the depths of winter when you want guaranteed heat without the fuss.