Will your propane last the winter? A pre-freeze plan for the property

A tank gauge is a snapshot. It tells you what you have today and nothing about February, which is the month that actually decides whether you spent the winter comfortable or spent it watching a dial. The useful question is not how full is the tank but how many times will I fill it, and what will those fills cost — and that is a season-scale question three hour-scale calculators can answer in sequence.

Work it in that order. Load first, because everything downstream is a multiple of it. Then refills, because a tank that covers 40 percent of the season is a delivery schedule, not a supply. Then price, because propane is the one input you can still change after the arithmetic is done.

Step 1 — What the season burns

Seasonal load is the appliance’s rating multiplied by the hours it actually runs, not the hours in the season. That distinction is most of the error in home estimates. A furnace rated 80,000 BTU/hr across a 150-day heating season sees 3,600 hours of calendar, but a thermostat in a moderately cold climate calls for perhaps 30 percent of them — about 1,080 run hours. That is 86.4 million BTU, or roughly 944 gallons.

If you would rather not guess at duty cycle, take it from last year’s delivery tickets: total gallons burned is the one number that already has your climate, your insulation and your thermostat habits baked into it. Use the calculator to test changes against that baseline — a second appliance, a colder forecast, a warmer setpoint.

Step 2 — How many fills that is

Now divide the season by the tank. The trap is using the number painted on the side: a 500-gallon tank is a 400-gallon tank in practice, because NFPA 58 caps the fill at 80 percent of water capacity to leave the liquid room to expand. Against 944 gallons of demand, 400 usable gallons per delivery is 2.4 fills — and nobody sells a four-tenths delivery, so the real answer is three.

Rounding up is not pedantry here, it is the scheduling constraint. At about 6.3 gallons a day, a 400-gallon fill runs roughly 63 days — so the deliveries fall around day 1, day 64 and day 127, one every nine weeks, and the last of them lands in the back half of winter when routes are busiest and the weather is least cooperative. Knowing that in September is the entire advantage: it is the difference between booking a delivery and requesting an emergency one.

Step 3 — What it costs, and when to buy it

At $3.00 a gallon, 944 gallons is about $2,830of fuel. Price is the lever with the most travel in it, because residential propane is seasonal on the way up: EIA’s weekly survey runs October through March precisely because that is when the market moves, and it generally moves against the buyer. Pre-buy contracts, summer-fill pricing and budget plans all exist to sell you next winter’s gallons at this autumn’s number.

Whether that is worth it is arithmetic you can now actually do. You have a gallon figure; price it at the pre-buy rate and at a plausible midwinter rate, and the spread is what the contract is worth. Run it before you sign, not after — and note that a pre-buy only pays if your estimate is honest, since committing to gallons you don’t burn is its own kind of loss.

The same deadline closes the pool

Propane planning is calendar-driven, and it shares its deadline with the other job that has to happen before the first hard freeze. Closing a pool is not a cold-weather task you can postpone into cold weather: winterizing chemicals are dosed to hold water that is already cooling, and plumbing left full is plumbing that splits. Both jobs want the same weekend in early autumn, which is why they belong on one list.

If the pool has a propane heater, the two are the same decision rather than two neighbouring ones — every week you extend the swimming season is gallons off the winter allocation you just calculated, and it is worth pricing that trade explicitly before you decide when to close.

Common questions