Wood or Coal in a Stove: Which Burns Longer and Which Is Cheaper?

Short answer: coal gives more heat per kilo and burns longer in a stove. Seasoned wood (20% moisture) gives about 4.1 kWh/kg, or ≈3,500 kcal/kg; Soma lignite gives 4,800–5,200 kcal/kg according to its bag declaration. For the same heat, about 1.4–1.5 kg of wood replaces 1 kg of Soma coal. Wood lights easily, burns fast with flame and leaves little ash.

Current prices and types: Coal prices → · Firewood prices →

Does wood or coal give more heat?

According to Forest Research, stacked air-dry logs (20% moisture) have a net calorific value of 4.1 kWh/kg; 4.1 × 860 ≈ 3,500 kcal/kg. Coal varies by type. For details see how many calories firewood has and how many calories coal should have.

Which burns longer?

Coal. First, density: the same firebox holds about 3–5 times more energy with coal (6,400 ÷ 2,000 ≈ 3.2; 7,300 ÷ 1,400 ≈ 5.2). Second, how it burns: according to a guide adapted from Iowa State Extension, heated wood breaks down and gives off flammable gases that carry more than half of its heat; these burn quickly as flame and leave embers. A wood stove therefore needs frequent refuelling.

The guide of Türkiye Kömür İşletmeleri (TKİ, the state coal company) calls for top-down burning: fill the stove two-thirds with coal, light it with pieces of wood placed on top, and never add coal to a stove that is already burning. One load is planned to last a long time. Steps: how to light a coal stove.

Which is cheaper?

Compare cost per useful kWh, not price per kilo: cost per kWh = price per kg ÷ (kcal/kg ÷ 860) ÷ stove efficiency. The EU Ecodesign regulation (2015/1185) sets a minimum efficiency of 65% for closed solid-fuel stoves burning fuels other than pellets; if wood and coal burn in the same closed stove, efficiency cancels out and the decision comes down to the calorie ratio. Wood breaks even only if its price per kilo is at most this share of the coal price (3,500 ÷ coal kcal):

• Lignite (3,800–4,500 kcal/kg): wood at 78–93% of the coal price per kilo or less.
• Soma (4,800–5,200 kcal/kg): 68–73% or less.
• Siberian (7,000–7,800 kcal/kg, dry basis): 45–50% or less. Dry-basis values exceed as-delivered ones, so the real ratio is a bit higher.

Take per-kilo prices from the cards below or the price list and put them into the formula. For seasonal quantities use the fuel calculator and how much fuel should I buy.

Which one suits your stove?

Check the manual first. Multi-fuel stoves that also burn coal have, as the manufacturer Stovax describes, a raised grate, an ashpan below and a primary air inlet that brings air from beneath the grate. Do not burn coal in a wood-only stove without a grate. A pellet stove takes neither wood nor coal; pellet vs coal stoves is a separate topic: pellet stove or coal stove.

Is wood or coal more poisonous?

Both can poison. According to the CDC, carbon monoxide forms whenever fuel burns, including in stoves. The Ecodesign regulation sets the same carbon monoxide limit for wood and coal in closed stoves: 1,500 mg/m³ (at 13% O₂). Coal smoke also carries sulfur dioxide, nitrogen oxides, particulates and mercury (EIA); the WHO recommends against using unprocessed coal in homes. No fuel is smokeless.

• Have the chimney cleaned at least once a year (TKİ).
• Burn top-down; never add coal to a burning stove, and at bedtime put it out if possible or leave the lower air inlet and flue damper open (TKİ).
• Never keep a not fully extinguished ash bucket indoors (TKİ).
• Install a carbon monoxide detector near sleeping areas (CDC).
• If anyone has a headache, dizziness or weakness, ventilate, get them into fresh air and call 112 (Turkish Ministry of Health). Details: stove gas symptoms and carbon monoxide detectors.

What does it depend on?

• Type of coal: the calorie gap between lignite and imported coal changes the comparison completely.
• Wood moisture: 4.1 kWh/kg applies at 20% moisture; green wood gives less heat.
• Stove design: grate, air inlets, seals.
• Storage space: a tonne of wood takes more than twice the space of a tonne of coal.

Frequently asked questions

Is it better to burn wood or coal in a stove?

Coal if you want long, steady heat and your stove is rated for it; wood for quick lighting, little ash and short heating. Most users light coal with wood.

How much wood equals 1 tonne of coal?

By calorific value, 1 tonne of Soma coal (4,800–5,200 kcal/kg) equals about 1.4–1.5 tonnes of wood at 20% moisture (4,800 ÷ 3,500 ≈ 1.37; 5,200 ÷ 3,500 ≈ 1.49).

Can wood and coal be burned together?

Coal is lit with wood anyway (TKİ). In a multi-fuel stove, yes; but do not add coal to a burning stove; light a new load top-down after the stove has gone out.

Which produces less ash?

Wood: firewood with bark leaves 1.0–1.2% of its dry weight as ash; coal leaves 12–28% according to bag declarations.

Wood or charcoal for a barbecue?

Barbecues use charcoal made from wood, not stove coal: how to light charcoal.

Sources: calorific value, density and energy per volume Forest Research, "Typical calorific values of fuels"; wood ash COFORD, "Wood ash"; ster weight OGM, ster conversion; minimum efficiency and carbon monoxide limit (EU) 2015/1185 Ecodesign, Annex II; top-down burning and safety TKİ, coal stove guide; stages of wood combustion University of Arizona / Iowa State Extension; grate Stovax; coal emissions EIA; WHO, household air pollution; wood moisture EPA Burn Wise; carbon monoxide CDC and Turkish Ministry of Health. Coal values are product bag declarations. Conversion: 1 kWh = 860 kcal.