Heater Fuel Runtime Calculator (Diesel & Gas)

Estimate how long a diesel or gas (LPG) van heater will run on a tank or bottle, from the heat output you actually use. The maths runs entirely in your browser — nothing you type is sent or stored.

Methodology

Rather than guessing a single L/h figure (every heater — Webasto, Eberspächer, Autoterm, Truma, Alde — has its own burn curve), this calculator derives consumption from the physics of the fuel itself: how much usable heat a litre of diesel or a kilogram of LPG actually contains.

Consumption rate (L/h or kg/h) = heat output (kW) ÷ (fuel calorific value (kWh per unit) × combustion efficiency).
Diesel calorific value ≈ 10.7 kWh/L — a published fuel-conversion figure, e.g. the UK Government's GHG conversion factors.
LPG/propane calorific value ≈ 12.8 kWh/kg (net) — a typical figure published by LPG suppliers.
Combustion efficiency (default 85%) is a typical figure for forced-air van heaters — a rule of thumb attributed here, not a spec for any one model. Check your exact unit's datasheet for its rated efficiency.
Runtime (days) = tank/bottle capacity ÷ (consumption rate × hours run per day).

This calculator gives a planning estimate from fuel physics, not a manufacturer-tested burn rate. Actual consumption varies by altitude, ambient temperature, heater condition and thermostat cycling. Cross-check against your specific model's datasheet (Webasto, Eberspächer, Autoterm, Truma, Alde all publish consumption tables) before planning a remote trip around it.

Methodology

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