How many pellets, how much coal or how many briquettes you need per heating season
A season's stock is not calculated "the way the neighbours do it" but from the house's heat loss: floor area, insulation, region and boiler efficiency. Below is a simple three-step method and a ready-made table for typical houses.
Step 1. How much heat the house loses over a season
The simplest estimate uses the specific heat loss per square metre over the heating season. For Ukraine (a season of 180-200 days, an average seasonal temperature of about 0 °C) the guide figures are:
| House | Heat loss, kWh/m² per season |
|---|---|
| New, insulated (walls with 150 mm mineral wool or 100 mm EPS, double-glazed windows, insulated roof) | 70-100 |
| Brick or aerated concrete without wall insulation, new windows | 120-160 |
| Old, uninsulated, single-glazed windows, cold loft | 180-250 |
Example: an insulated 120 m² house loses 120 × 90 = 10,800 kWh over a season. An old house of the same area loses 120 × 220 = 26,400 kWh, 2.5 times more. The region adjusts the figure by ±15%: in the South take the lower end, in the North and West the upper end.
Step 2. How much heat a kilogram of fuel gives in your boiler
Multiply the fuel's calorific value by the boiler efficiency. Typical values:
| Fuel | kWh/kg | Boiler and efficiency | Useful, kWh/kg |
|---|---|---|---|
| Anthracite | 8.5 | forced draught, 0.85 | 7.2 |
| Long-flame coal DG | 7.0 | conventional, 0.78 | 5.5 |
| Wood pellets | 4.8 | pellet boiler, 0.90 | 4.3 |
| RUF, Pini-Kay briquettes | 4.8 | conventional, 0.78 | 3.7 |
| Peat briquettes | 4.0 | conventional, 0.75 | 3.0 |
| Dry firewood | 3.6 | conventional, 0.75 | 2.7 |
If you heat with a stove rather than a boiler, take an efficiency of 0.6: consumption will rise by about a quarter.
Step 3. Divide one by the other
Stock, tonnes = seasonal heat loss, kWh ÷ (useful kWh/kg × 1000)
For an insulated 120 m² house (10,800 kWh): anthracite 10,800 ÷ 7,200 = 1.5 t; pellets 10,800 ÷ 4,300 = 2.5 t; briquettes 10,800 ÷ 3,700 = 2.9 t; peat briquettes 10,800 ÷ 3,000 = 3.6 t. For an old house of the same area (26,400 kWh): anthracite 3.7 t, pellets 6.1 t, briquettes 7.1 t, peat 8.8 t.
Add a 10-15% reserve to the result for a frosty winter and for the fuel you will burn for hot water if the boiler also heats water.
Ready-made table: consumption per season, tonnes
Average values for a house with normal insulation (130 kWh/m²) and a boiler of the appropriate type, with a 10% reserve. For an insulated house subtract 30-35%, for an old one add 50-70%.
| Floor area | Anthracite | DG | Pellets | Briquettes | Peat briquettes |
|---|---|---|---|---|---|
| 80 m² | 1.6 | 2.1 | 2.7 | 3.1 | 3.8 |
| 100 m² | 2.0 | 2.6 | 3.3 | 3.9 | 4.8 |
| 120 m² | 2.4 | 3.1 | 4.0 | 4.6 | 5.7 |
| 150 m² | 3.0 | 3.9 | 5.0 | 5.8 | 7.2 |
| 180 m² | 3.6 | 4.7 | 6.0 | 6.9 | 8.6 |
| 200 m² | 4.0 | 5.2 | 6.6 | 7.7 | 9.5 |
| 250 m² | 5.0 | 6.5 | 8.3 | 9.6 | 11.9 |
Converting tonnes into bags, pallets and big bags
- 25 kg bag (coal, peat briquettes): 40 bags per tonne.
- 15 kg bag (pellets): 66-67 bags per tonne; a pallet holds 65-70 bags, about 1 t.
- 10 kg pack of briquettes: 100 packs per tonne; a pallet holds 96 packs, about 960 kg.
- Big bag: about 1,000 kg for coal, pellets and peat.
- Bulk: weighed on the warehouse scales; a tipper truck usually carries from 5 tonnes.
So 3 tonnes of anthracite means 120 bags or 3 big bags; 5 tonnes of pellets means 5 pallets; 6 tonnes of peat briquettes means 240 bags or one tipper truck load.
How much space it will take
Bulk density will tell you whether your stock will fit in the shed: anthracite 0.9-1.0 t/m³, DG 0.8-0.9 t/m³, pellets 0.65 t/m³ (a 1.2×0.8 m pallet stands 1.8 m high), briquettes on a pallet about 1 t/m³, peat briquettes 0.7-0.8 t/m³. Pellets and briquettes must be stored under a roof only, coal can cope with a lean-to shelter, and peat needs a dry room.
Why your neighbour's figures are different
There are three reasons for the discrepancy. The first is the indoor temperature: every degree above 20 °C adds 5-6% to consumption. The second is fuel moisture: green firewood or damp pellets give a third less heat. The third is how you run the fire: anthracite smouldering with the draught turned down is used more economically than at "full throttle". So the table is a guide for purchasing, and you will see the exact figure after the first season if you keep count of the bags.
If you would rather not do the maths yourself, give us a call: based on the floor area, year of construction and boiler model, we will calculate your stock and suggest packaging that is convenient to store.
Questions and answers
How many tonnes of pellets do I need for the winter for a 100 m² house?
A 100 m² house with normal insulation (about 130 kWh/m² per season) and a pellet boiler needs about 3.3 t of pellets including a 10% reserve. An insulated house will need 30-35% less, i.e. about 2.2 t, while an old uninsulated one will need 50-70% more, 5-5.6 t. The exact figure comes from calculating your house's heat loss.
How much coal do I need for the winter for a 100-120 m² house?
A house with normal insulation needs roughly 2.0 t of anthracite or 2.6 t of DG coal per season for 100 m², and 2.4 t of anthracite or 3.1 t of DG for 120 m². Anthracite gives more useful heat per kilogram (about 7.2 kWh in a forced-draught boiler versus 5.5 for DG), so you need less of it. For an old uninsulated house, multiply these figures by 1.5-1.7.
How can I calculate my own fuel consumption for the heating season?
Multiply the floor area by the specific heat loss: 70-100 kWh/m² for an insulated house, 120-160 for an uninsulated brick house, 180-250 for an old one. Divide the result by the useful heat per tonne of fuel: 7,200 kWh for anthracite, 4,300 for pellets, 3,700 for briquettes. For example, an insulated 120 m² house: 10,800 ÷ 4,300 = 2.5 t of pellets; add a 10-15% reserve to the result. The calorific values of different fuels are collected in the article fuel calorific value.
How many bags of pellets are in a tonne and how many pallets do I need per season?
A tonne holds 66-67 bags of 15 kg pellets, and one pallet holds 65-70 bags, i.e. about 1 t. So a 5 t stock of pellets means 5 pallets. Coal and peat briquettes in 25 kg bags come to 40 bags per tonne, briquettes in 10 kg packs to 100 packs per tonne.
How much space does a tonne of pellets, coal or briquettes take up?
The bulk density of pellets is about 0.65 t/m³, so a tonne takes up roughly 1.5 m³ (one 1.2 × 0.8 m pallet, 1.8 m high). Anthracite weighs 0.9-1.0 t/m³, DG 0.8-0.9 t/m³, briquettes on a pallet about 1 t/m³, peat briquettes 0.7-0.8 t/m³. How to store your stock so the fuel does not get damp is explained in the article how to store pellets, coal and briquettes.
Why does my neighbour with the same house use a different amount of fuel?
Every degree of indoor temperature above 20 °C adds 5-6% to consumption. Green firewood or damp pellets give a third less heat, and how you run the fire matters too: anthracite smouldering with the draught turned down is used more economically than at full power. So the tables are a guide for purchasing, and the exact figure becomes clear after the first season if you keep count of the bags.
Buy the fuel covered in this article
Prices per tonne and per bag, stock and delivery across Ukraine are on the category page. For wholesale: special terms.