Siltuma Cena editorial · Published
Useful heat and a realistic pellet stock estimate
Price per tonne measures fuel cost. Price per useful MWh also depends on fuel energy and how much of it your heating system delivers. A stock estimate answers a different question: how long the bags may last.
Make the energy assumptions visible
Use these fictional assumptions only to follow the arithmetic: €300/t for pellets, 4.8 kWh/kg of fuel energy and 85% seasonal efficiency. One tonne contains 4,800 kWh, or 4.8 MWh, before losses. Useful heat is 4.8 × 0.85 = 4.08 MWh. Fuel cost is therefore €300 ÷ 4.08 = €73.53 per useful MWh.
If efficiency were 75% with the other inputs unchanged, useful heat would fall to 3.6 MWh and cost would rise to €83.33/MWh. These percentages are examples, not measurements of your boiler. Use the product’s declared energy value and a defensible system assumption. Include confirmed delivery costs in the fuel price if you want delivered heat cost; electricity, servicing and equipment costs remain separate.
Treat the stock date as a moving estimate
The site’s stock planner uses 15 kg bag equivalents. Forty such bags contain 600 kg. At an assumed 20 kg/day, that is 30 whole days; at 30 kg/day, it is 20. If your bags weigh 10 kg, convert the total mass first: forty 10 kg bags equal about 26.67 of the planner’s 15 kg units. Do not enter the unconverted count.
The planner suggests ordering ten days before estimated depletion. That is a planning buffer, not a supplier lead-time guarantee. Weather, hot-water use, boiler settings and empty or partly used bags can shift consumption. Record how much you actually use over several days and update the input after a cold spell. A calculated end date does not verify physical stock, moisture condition, delivery availability or the amount already in the hopper.
| Calculation | Result |
|---|---|
| 4.8 MWh/t × 85% | 4.08 useful MWh/t |
| €300 ÷ 4.08 | €73.53/useful MWh |
| 40 × 15 kg ÷ 20 kg/day | 30 days |
Questions for the seller
- What energy value is declared for this exact product?
- Does my consumption record include domestic hot water?
- What delivery lead time should I allow before the stock runs out?