Advanced options
Assumes 75% stove efficiency and seasoned wood at about 4 kWh per kg (under 20% moisture). Buying by the loose cubic metre? Hardwood runs roughly 300-400kg per loose m3. Burn only dry "Ready to Burn" certified wood: wet wood wastes heat, tars the flue and breaks air quality rules.
What The Log Burner Running Cost Calculator Works Out
- Wood used per week: burning hours x stove output x an average load of 60% of rated (stoves are damped down more than they roar) gives heat delivered; dividing by 75% efficiency and 4 kWh per kg of dry wood gives kilograms of logs. A 5kW stove for 20 hours a week delivers about 60 kWh and burns roughly 20kg.
- Cost per week: kilograms x the price per tonne, with the pence per kWh of delivered heat underneath. Wood at GBP 250 a tonne lands near 8p per kWh of heat, between gas and electricity, which is why a burner is a lifestyle and resilience purchase more than a money-saver against mains gas, but a genuine saver against electric heating or off-grid oil.
- Heating season: the weekly cost x 30 weeks (editable in advanced options), with the tonnage you will need to store. A fiver or so a week makes GBP 150 to GBP 300 a season.
- Load, efficiency and dryness (advanced): edit the damped-down percentage, the stove's efficiency (Ecodesign stoves reach 80% plus, old open fires 20% to 30%) and the energy content of the wood. Wood above 20% moisture wastes energy boiling water, coats the flue in tar and smokes the neighbourhood; a GBP 10 moisture meter and the Ready to Burn mark police the line.
- Same heat from gas or electricity (advanced): the season's delivered heat priced through a 90% efficient gas boiler at your gas rate, and through a 100% efficient electric heater at your electricity rate, each with the saving or extra cost against wood.
- Loose load price per tonne (advanced): converts a price per loose cubic metre (hardwood runs 300 to 400kg per loose cube) into a per-tonne figure, plus the loads you need a season. Kiln-dried nets and garage bags are the expensive way to buy the same heat, loose loads the cheap one, and buying green wood a year ahead to season yourself cheaper still.
- Cost of burning damp wood (advanced): the extra spent per season if the same price buys 30% moisture logs at 3 kWh per kg and the stove loses ten points of efficiency to a cooler, smokier burn.
- Rules worth knowing: new stoves must be Ecodesign compliant; most urban areas are Smoke Control Areas where only exempt appliances or authorised fuels are legal; wet wood and house coal are no longer sold for home burning; sweep the chimney at least annually; and a carbon monoxide alarm is legally required with any new solid fuel installation.