Why Do Coal and Firewood Prices Change? Calorific Value, Moisture, Kg vs Tonne and Season

Short answer: firewood and coal prices mostly reflect the heat you get per kilo. The UK's Forest Research says well-seasoned wood gives about 2 times the heat of freshly cut wood; coal bag declarations range from 3,800 to 8,200 kcal/kg. Delivery terms, bagged or bulk buying and the season add to that. Current figures are in the live list below.

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

What determines firewood and coal prices?

When you buy fuel you are really buying heat, not weight. That is why setting two bag or tonne prices side by side is misleading; the real comparison is cost per unit of heat. All the factors below can be measured:

How does moisture change the price of firewood?

According to Forest Research's “Wood as Fuel” guide, moisture has the greatest effect on the net calorific value of wood: the water in it has to evaporate before the wood burns, and that heat goes up the chimney as steam. The guide says well-seasoned logs can have approximately twice the calorific value of green logs. So a kilo of cheap but wet wood can deliver more expensive heat than a kilo of dry wood that looks dearer. The same guide notes that many manufacturers specify 20% moisture or less, which can take two summers or more of air drying.

When comparing quotes, ask about moisture first: our product declarations list oak firewood at 15–20% and six-month oak at 25–30% moisture. We explain how to spot wet wood in how to season firewood and heat values by species in how many calories firewood has.

How does calorific value change the price of coal?

Higher-calorie coal burns fewer kilos for the same heat. The arithmetic is simple: since 1 kWh = 860 kcal, coal at 7,000 kcal/kg gives about 8.1 kWh per kilo (7,000 ÷ 860) and coal at 4,000 kcal/kg about 4.7 kWh (4,000 ÷ 860). Divide the price per kilo by kWh per kilo and you have the cost per kWh. The Manisa Provincial Directorate of Environment and Urbanisation also notes that imported coal has a high calorific value and low sulphur.

See how many calories coal should have for minimum values, and wood or coal in a stove for comparing heat and burn time.

Price per kg or per tonne: how do you compare?

“How much is a kilo of firewood?” and “how much is a tonne of coal?” convert into each other with the same sum. Divide a tonne price by 1,000, or a bag price by the bag weight, and you get the price per kg.

We cover ster-to-tonne conversion for firewood in how many sacks and sters in 1 tonne of firewood, and tonne and bag sums for coal in the price of 1 tonne and 1 bag of coal.

Why do delivery, bags and bulk buying change the price?

Heating fuel is heavy; carrying and handling are a real part of the final price. Whether the truck can reach your door, which floor it goes to, whether porters are needed and how much you order at once all change the total. Forest Research also advises asking whether a quote includes delivery and whether you are buying by weight or by volume. Bulk can be cheaper per unit if you have a dry store; bulk fuel that gets wet takes the saving back.

How do the season and imported coal affect the price?

Demand is not spread evenly across the year; when the weather turns cold, orders bunch up and well-seasoned stock runs out faster. The measurable benefit of buying early is that wood stacked under cover with airflow keeps drying until you start burning it. The price of imported coal also depends on exchange rates, freight and port costs on top of the coal itself, so it can move more than domestic coal during the season.

What does it depend on?

• Moisture: The biggest driver of heat per kilo in firewood.
• Calorific value and its basis: kcal/kg for coal, and whether it is dry basis or as received.
• Unit of sale: Kg, tonne, bag or ster; convert to the same unit before comparing.
• Delivery terms: Floor, truck access, porters and quantity.
• Permit: For coal, the Sales Permit and the declaration on the bag.
• Season: In the busy period choice narrows.

Where are the current prices?

We deliberately quote no figures here; a price written into an article goes stale from the day it is published. Current per-kg, per-bag and per-tonne prices for firewood and coal are in the live list directly below this article and on our price list page. Work out how much fuel you need for the winter with our fuel calculator and multiply by the price per kg.

Frequently asked questions

How do you work out the price of a kilo of firewood?

Divide a tonne price by 1,000, or a sack price by the sack weight. For a 30 kg sack, sack price ÷ 30 gives the price per kg. Current figures are on the price list.

How many sacks are in 1 tonne of oak firewood?

It depends on the sack weight: 1,000 ÷ 30 ≈ 33.3 sacks of 30 kg, or 40 sacks of 25 kg. For sters, see our article on how many sters are in 1 tonne of firewood.

Why can cheap firewood end up expensive?

Part of the weight of wet wood is water. According to Forest Research, freshly cut wood gives around half the heat of well-seasoned wood, so the heat you pay for per kilo can cost more.

Why does the price per kilo of coal vary so much?

Because calorific value varies: bag declarations range from 3,800 to 8,200 kcal/kg. Compare by dividing the price per kg by the heat per kg.

Should you buy coal by the tonne or by the bag?

The arithmetic is the same: with 25 kg bags, 1 tonne = 40 bags.

Sources: Forest Research (UK), “Typical calorific values of fuels” (wood 4.1 and 5.3 kWh/kg, house coal 7.5–8.6, anthracite 9.2 kWh/kg, densities); Forest Research / Biomass Energy Centre, “Wood as Fuel: A Guide to Choosing and Drying Logs” (effect of moisture, about twice, 20% moisture, delivery and unit questions); Manisa Governorship, Provincial Directorate of Environment and Urbanisation, “Information Note on Air Pollution” (Sales Permit, calorific value and sulphur of imported coal); Official Gazette of Turkey, “Regulation on the Control of Solid Fuels for Air Quality” (Art. 11: Sales Permit and bagged sale).