RV Propane Duration Calculator

This calculator estimates how many days a propane tank will last by comparing its total energy content against the combined daily draw from the furnace, water heater, and stove. Outside Temperature is by far the biggest real driver of Tank Runtime, even though it doesn't read that way from a small nudge around its default: the furnace's assumed daily runtime jumps in four discrete bands -- 18 hours below 20°F, 12 hours from 20-40°F, 6 hours from 40-60°F, and just 1 hour above 60°F -- so Tank Runtime only actually moves once the temperature crosses one of those band edges, not with every small change. At the coldest band, the same tank lasts roughly a day; in mild weather it can stretch past a week and a half. Within Propane Tank Size and Furnace BTU Rating, the two inputs that do respond smoothly, Propane Tank Size has the larger true effect on Tank Runtime: it's a pure linear multiplier of the tank's total energy, while Furnace BTU Rating's effect is partly offset because it's only part of a larger daily-usage total that also includes the water heater and stove.

Furnace BTU Rating, in turn, dominates Daily BTU Consumption, Gallons Per Day, and Cost Per Day, since at the default settings the furnace burns roughly nine times as much propane per day as the water heater does. Propane Tank Size has no effect on any of those three daily-usage figures at all -- tank size only changes how long the supply lasts, not how fast it's consumed. This is a planning estimate -- actual usage varies with insulation quality, wind exposure, and how often doors and vents are opened.