Propane Tank Size Calculator

Two separate questions: peak load and annual usage

Sizing a propane tank actually involves two different calculations that often get conflated: total connected load (the sum of every appliance’s maximum BTU-per-hour draw, which matters for whether the system can deliver enough propane pressure and flow when everything runs at once) and annual usage (how many gallons you’ll actually burn over a year, which drives how often you need deliveries). This calculator tracks both from the same appliance checklist, so a bigger household with more or larger appliances sees both numbers move together, rather than sizing off a single vague “how big is your house” heuristic.

Building an honest appliance checklist

The appliances that typically run on propane in a residential setting — furnace, water heater, range or cooktop, clothes dryer, fireplace, and less commonly a pool or spa heater and a standby generator — each carry a specific BTU-per-hour rating on their nameplate that can vary meaningfully by model and size. This calculator starts with reasonable typical values for each category, but the actual nameplate rating on your specific appliances is the number that matters for an accurate estimate — check the data plate rather than assuming a generic figure, especially for larger items like a furnace or pool heater where the range between a small unit and a large one is substantial.

Why a pool heater or generator changes the picture so much

Pool and spa heaters and standby generators carry disproportionately large BTU-per-hour ratings compared to everyday appliances — a pool heater alone can rival or exceed a home’s furnace in peak draw, even though it runs far fewer hours per year. Adding either of these to a household’s propane setup is frequently what pushes a recommendation from a smaller 250-gallon tank up to 500 gallons or larger, since the connected load calculation has to account for the possibility of that appliance running at its full rated draw, even if it’s not running constantly.

The 80% rule: why a “500-gallon” tank isn’t really 500 gallons of usable propane

Propane expands measurably as it warms, and a completely full liquid tank would have no room for that expansion — which is why propane tanks are, by design and by code, filled to only about 80% of their stated water capacity. A tank labeled 500 gallons delivers roughly 400 gallons of usable propane per full fill. This matters directly for planning delivery frequency: dividing this calculator’s estimated annual gallon usage by the tank’s usable capacity (not its nameplate size) gives a more accurate sense of how many deliveries a typical year requires.

Supplier-owned versus customer-owned tanks

Many residential propane customers don’t actually purchase their tank outright — a supplier installs and owns the tank as part of an ongoing service and delivery agreement, which is common for smaller residential tank sizes and removes tank maintenance and inspection responsibility from the homeowner. Larger installations, or homeowners who want the flexibility to shop between suppliers for the best delivery price, sometimes purchase their own tank instead. Ask local propane suppliers directly about which arrangement they offer and what it costs, since this varies by company and region and affects the real total cost of a propane setup beyond just tank size. See the HVAC BTU calculator for sizing the furnace load that often dominates this calculation, and the energy cost calculator for comparing propane’s ongoing cost against other heating fuel options.