Heating Fuel Cost Comparison Calculator (Pellets, Oil, Gas, Wood, Electricity)
The true cost of one kWh of heat from two fuels sold in different units, the yearly bill for each, the saving and the price at which they would break even.
Results
The dashed line marks the value you entered.
What this tool does
Fuels are sold by the kilo, litre, cubic metre or kWh, so sticker prices cannot be compared — what matters is the price of a kWh of heat that actually reaches the room. That is the price per unit divided by the energy in a unit and by the efficiency of the appliance. Wood pellets are commonly quoted at around 4.8–5 kWh/kg, heating oil near 10 kWh/L and natural gas around 10–11 kWh/m³ (check your supplier), while firewood varies with how dry it is. Efficiency matters as much as price: a modern condensing boiler or pellet stove returns most of the energy as heat, an open fire sends much of it up the chimney.
Formula
cost per kWh of heat = price ÷ (energy per unit × efficiency) · yearly cost = heat needed × cost per kWh
Variables
| Symbol | Meaning | Unit |
|---|---|---|
dem | Heat you need in a year | kWh |
pa | Fuel A — price per unit (kg, litre, m³ or kWh) | — |
ea | Fuel A — energy in one unit | kWh |
xa | Fuel A — efficiency of the appliance | % |
pb | Fuel B — price per unit (kg, litre, m³ or kWh) | — |
eb | Fuel B — energy in one unit | kWh |
xb | Fuel B — efficiency of the appliance | % |
SV | Yearly saving of the cheaper one | — |
CH | Cheaper way to heat | — |
CA | Fuel A — cost of one kWh of heat | — |
CB | Fuel B — cost of one kWh of heat | — |
YA | Fuel A — cost over a year | — |
YB | Fuel B — cost over a year | — |
UA | Fuel A — units burned in a year | — |
UB | Fuel B — units burned in a year | — |
BE | Price of fuel B at which both cost the same | — |
Worked example
- Heat you need in a year15,000 kWh
- Fuel A — price per unit (kg, litre, m³ or kWh)0.4
- Fuel A — energy in one unit4.8 kWh
- Fuel A — efficiency of the appliance85 %
- Fuel B — price per unit (kg, litre, m³ or kWh)1.1
- Fuel B — energy in one unit10 kWh
- Fuel B — efficiency of the appliance90 %
- Yearly saving of the cheaper one363
- Cheaper way to heatFuel A
- Fuel A — cost of one kWh of heat0.0980
- Fuel B — cost of one kWh of heat0.1222
- Fuel A — cost over a year1471
- Fuel B — cost over a year1833
- Fuel A — units burned in a year3676
- Fuel B — units burned in a year1667
- Price of fuel B at which both cost the same0.882
Limitations
- Prices and emission factors are yours to enter. The tool ships with no tariff table and assumes nothing about your country or supplier, so change the defaults to match your own bill.
- Coverage and consumption figures vary between products. Take the values from the manufacturer's datasheet for the product you are actually using.