Anthracite or long-flame coal: which to choose for a boiler or stove
Anthracite gives more heat and burns longer; long-flame coal is easier to light and works in any stove. Which of the two is more cost-effective for you depends on the draught of your boiler and on how you heat: once every twelve hours or several times a day.
The essential difference
Both are coal, but from different stages of "maturity". Long-flame coal (DG, ДГ) is young bituminous coal with 35-45% volatile matter: gases and tars that are released when heated and burn with a long flame. Anthracite is the oldest coal, with 2-8% volatiles and almost pure carbon. That is why anthracite burns without a flame, as a glowing bed, while long-flame coal burns like firewood, with fire and smoke. All the practical differences follow from this.
| Parameter | Anthracite | Long-flame coal DG |
|---|---|---|
| Calorific value | 7,000-8,000 kcal/kg (8-9 kWh) | 5,500-6,500 kcal/kg (6.5-7.5 kWh) |
| Burn time per load | 8-12 hours | 4-6 hours |
| Lighting | difficult, on a bed of firewood or DG | from paper and kindling |
| Draught | strong draught needed: forced draught or a chimney of 6 m or more | natural draught is enough |
| Smoke and soot | almost none | noticeable, the chimney needs cleaning more often |
| Ash content | 10-15% | 10-20% |
| Carbon monoxide with weak draught | high risk: it smoulders | lower risk, but it exists |
| Price per tonne | higher | lower |
| Price per kWh | close to DG, sometimes lower | close to anthracite |
Draught is the main criterion
Anthracite does not burn on its own: the bed needs a constant flow of air from below, otherwise it smoulders, the temperature drops and carbon monoxide forms. There are two sources of draught: a forced-draught fan with a controller, or a tall chimney (6 metres or more, straight and insulated). If your boiler has forced draught, anthracite will work as intended. If the boiler is a simple one, the chimney is short or has bends, or you have a stove or pot-belly stove, choose long-flame coal: it will catch and burn on whatever air is available.
A quick on-site check: light some firewood, close the door and open the ash-pit damper. If the flame roars and pulls upwards, the draught is good and anthracite will do. If it burns sluggishly and smoke comes into the room when you open the door, there is not enough draught for anthracite.
How you heat
Once every twelve hours, morning and evening. Anthracite: a single load of AO holds an even heat for 8-12 hours, and the boiler needs no attention during the day or night. DG cannot do this: a load burns out in 4-6 hours, and at three in the morning the house will be cold.
Several times a day while you are at home. Long-flame coal: it catches quickly, heats quickly and is easy to top up in small portions. Anthracite is inconvenient in this mode: lighting takes a long time, and a heated load is "wasted" if you do not use it.
A country house used at weekends. DG or peat briquettes: a cold house has to be warmed quickly, and anthracite cannot do that.
Working out the price of heat
Anthracite is more expensive per tonne but gives 20-30% more heat per kilogram. The formula: divide the price per tonne by the calorific value of a tonne. A hypothetical example: anthracite at 12,000 UAH/t with 8 kWh/kg gives 1.50 UAH per kWh; DG at 9,500 UAH/t with 7 kWh/kg gives 1.36 UAH per kWh. With this ratio DG is slightly more cost-effective; with a different price gap, anthracite is. Plug in the current prices from our categories and you will see which is better for your region.
Then factor boiler efficiency into the price of heat: in a boiler with forced draught anthracite burns more completely (80-85% efficiency), in a simple boiler DG delivers 70-80%, in a stove 50-60%. And allow for the ash: 15% ash content means you will carry out 150 kg of ash from every tonne of coal.
Common mistakes
Anthracite in a stove or fireplace. It smoulders, gives little heat and produces carbon monoxide. For stoves, use only long-flame coal, briquettes or firewood.
Closing the flue damper "so it burns longer". With anthracite this is dangerous: without air the bed smoulders and releases CO. Partly close the damper only when there are no blue flames left on the bed, and never close it completely.
Filling the firebox to the top with DG. The volatiles need air; a full firebox without it produces black smoke and soot. Add DG in portions onto a glowing bed.
Mixing in a single load. Sometimes this makes sense: DG at the bottom for lighting, anthracite on top. But you should not run a boiler with forced draught on a 50/50 mix of anthracite and DG: the controller is set up for one type of fuel.
The short answer
| Situation | Choice |
|---|---|
| Boiler with a forced-draught fan, you load it twice a day | Anthracite AO or AM |
| Automatic boiler with an auger | Anthracite AS |
| Simple boiler without forced draught | Long-flame coal DG 50-100 |
| Stove, masonry heater, pot-belly stove, sauna stove | Long-flame coal DG or briquettes |
| Country house at weekends | Long-flame coal or peat briquettes |
| Boiler house with mechanised feed | Anthracite AS/AM or DG 13-100, as per the boiler manual |
If you are not sure about your boiler's draught, buy a trial batch of a few bags each of DG and anthracite and see how they burn. That is cheaper than making a mistake with a whole tonne.
Questions and answers
Why does anthracite burn poorly or go out in my boiler?
The most common reason is weak draught. Anthracite needs a constant flow of air from below: a forced-draught fan or a straight, insulated chimney of 6 metres or more. Without this the bed smoulders, the temperature drops and carbon monoxide forms. Anthracite is lit on a bed of firewood or DG; lighting and air supply are covered in detail in the article how to heat with coal.
How long does one load of anthracite or long-flame coal burn?
A load of anthracite AO holds an even heat for 8-12 hours, so loading the boiler in the morning and evening is enough. Long-flame coal DG burns out in 4-6 hours and has to be topped up at night. On the other hand, DG catches faster and is better suited to heating several times a day.
Can I mix anthracite and long-flame coal?
Sometimes it makes sense: DG at the bottom for lighting, anthracite on top. But running a boiler with forced draught on a 50/50 mix is not a good idea: the controller is set up for one type of fuel.
How can I check whether the draught is strong enough for anthracite?
Light some firewood, close the door and open the ash-pit damper. If the flame roars and pulls upwards, the draught is good and anthracite will do. If it burns sluggishly and smoke comes into the room when you open the door, there is not enough draught for anthracite, so choose long-flame coal.
Which is cheaper per unit of heat: anthracite or DG?
Anthracite is more expensive per tonne but gives 20-30% more heat per kilogram. A hypothetical example: anthracite at 12,000 UAH/t with 8 kWh/kg gives 1.50 UAH per kWh, DG at 9,500 UAH/t with 7 kWh/kg gives 1.36 UAH. The result depends on the price gap, so plug in the current prices from the coal section and allow for your boiler's efficiency.
Why does long-flame coal produce black smoke and soot?
The volatile matter in DG (35-45%) burns completely only with enough air. If you fill the firebox to the top, there is not enough air, and the result is black smoke and soot. Add DG in portions onto a glowing bed, and clean the chimney more often than you would with anthracite.
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Prices per tonne and per bag, stock and delivery across Ukraine are on the category page. For wholesale: special terms.