Propane and Heating Oil Bills: When the Fuel Arrives by Truck
Why this matters
A gas or electric bill measures use over a billing period. A propane or heating oil bill measures a delivery. The ticket says how much fuel went into the tank on the day the truck came, and nothing about when that fuel was burned. A homeowner who gets a delivery three times the size of the last one assumes the new furnace burned three times as much, when the real difference may be that the truck stayed away twice as long. Read delivered-fuel bills the wrong way and you will chase a fault that is really a calendar.
Safety first on any propane call. If the customer smells gas, everyone leaves the house without touching switches, appliances or phones inside, and calls the propane supplier's emergency number or 911 from outside. If the tank has run completely empty, do not relight pilots or restart appliances. In many states, under rules adopted from NFPA 54 and NFPA 58 in the edition that state uses, the supplier must leak-check the system before service is restored after a run-out, and that is the supplier's job, not the service tech's.
The delivery ticket, laid out
DELIVERY TICKET 20417 DATE 01/19
PRODUCT: PROPANE TANK SIZE 1,000 GAL
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GAUGE BEFORE 40 % GAUGE AFTER 80 %
METER START 116,402.1 METER END 116,812.1
GALLONS DELIVERED 410.0 [1]
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PRICE PER GALLON P [2]
PRODUCT CHARGE 410.0 x P
DELIVERY OR HAZMAT FEE fixed, if any [3]
TANK RENTAL per year, if leased [3]
TAX percent, where it applies
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LAST DELIVERY 12/01 DAYS SINCE 49 [4]
DEGREE DAYS SINCE 1,250 [4]
[1] Gallons delivered comes from the truck's meter, not the tank gauge. 116,812.1 minus 116,402.1 is 410.0 gallons. The truck meter is the measurement that is certified by the state's weights and measures program. The tank gauge is an estimate: here it moved from 40 to 80 percent, which on a 1,000 gallon tank implies 40 percent of 1,000, or 400 gallons. The 10 gallon gap is normal float-gauge slop. When gauge and meter disagree, the meter wins.
Why a propane tank stops at 80 percent. Propane is stored as a liquid under pressure and expands substantially as it warms, so tanks are filled to about 80 percent of their water capacity to leave vapor space. A 1,000 gallon tank holds about 800 gallons of propane at most, and a 500 gallon tank about 400. That ceiling caps the largest delivery possible: this ticket's 410 gallons fits, but the same delivery could never go into a 500 gallon tank.
[2] Price per gallon. The rate depends on the customer's arrangement with the dealer: a market price on the day, a pre-bought price set before the season, a capped price, or a budget plan that spreads payments. Read the price line on each ticket rather than assuming it is the same. A cost comparison across a winter has to separate gallons from price before it says anything about equipment.
[3] Fees. Delivery, fuel surcharge, hazmat, minimum-delivery and tank rental charges vary by dealer. A small delivery carries the same fixed fee as a large one, which is why small will-call orders cost more per gallon all-in.
[4] Days and degree days since the last delivery. Not every ticket prints these. Dealers that schedule automatic deliveries track them because they predict when the tank will need filling. When they are on the ticket, they are the most useful lines on it.
Heat in a gallon
To compare a delivery with anything else, convert it to heat. Commonly used figures:
- Propane: about 91,500 BTU per gallon, so a gallon is about 0.915 therm.
- No. 2 heating oil: about 138,500 BTU per gallon, so a gallon is about 1.385 therms.
So 410 gallons of propane is 410 times 91,500, or about 37.5 million BTU, which is 375 therms. A gallon of oil carries about 1.5 times the heat of a gallon of propane (138,500 divided by 91,500 is 1.51), which is why gallon counts cannot be compared across the two fuels. Putting fuels on one cost scale belongs to a sibling (see related: How to Compare Heating Costs Across Fuels per Million BTU).
Worked example: the delivery that was 69 percent bigger
A customer had a new propane furnace installed in late October. Their 12/01 delivery was 242 gallons. Their 01/19 delivery, the ticket above, was 410 gallons. They call to say the new furnace is a fuel hog.
What the customer compared. 410 divided by 242 is 1.69. The January delivery was 69 percent bigger.
Was each delivery a refill to the same level? This is the gate. Dividing a delivery by the days since the last one only measures use if both deliveries filled the tank to the same point. Both tickets show "gauge after 80 percent," so each one replaced what was burned since the delivery before it. If one had been a partial fill (a customer who asked for a fixed number of gallons), the arithmetic below would not hold, and you would need the gauge readings to reconstruct use.
Gallons per day. The 12/01 delivery replaced 28 days of use: 242 over 28 is 8.64 gallons a day. The 01/19 delivery replaced 49 days: 410 over 49 is 8.37 gallons a day. 8.37 divided by 8.64 is 0.97. Per day, use fell 3 percent.
Check from the other side. At December's rate of 8.64 gallons a day, 49 days would have needed 8.64 times 49, or 423 gallons. The house took 410. That is 13 gallons less than December's pace, about 3 percent of 423. Same answer.
Per degree day. Heating degree days measure how cold a period was (see related: How to Weather-Normalize Two Winters of Bills). The December period had 700, the January period 1,250. 242 over 700 is 0.346 gallons per degree day; 410 over 1,250 is 0.328. 0.328 divided by 0.346 is 0.95, so per unit of cold the house used 5 percent less. Both periods ran close to 25 degree days a day (700 over 28, and 1,250 over 49, which is 25.5), so the per-day and per-degree-day answers agree in direction, and the January delivery is big because the truck stayed away 49 days instead of 28.
What to tell the customer. "Your January delivery covered 49 days, and the one before covered 28. Per day the house used about 3 percent less, and about 5 percent less once you allow for the weather. The big ticket is the gap between deliveries, not the furnace." Then stop. The figures are delivery-based estimates that include the water heater, range and dryer, not a measured furnace efficiency, and the honest limit of what this can show belongs in savings claims without overpromising (see related).
Heating oil tickets
Oil tickets look much the same, with differences that change how you read them.
Fills often go by whistle, not gauge. Many oil tanks have a vent alarm that whistles while air is being pushed out and stops when oil nears the top. The driver fills until it stops. The ticket may not show a gauge reading at all, only gallons and "fill." Two whistle-stop fills are close to refills to the same level, but a tank filled while the alarm was silent or missing is not.
Tank size is nominal. A common indoor tank is called 275 gallons, and it is never filled to its full nominal capacity. Do not read a 275 gallon tank as able to take a 275 gallon delivery.
The burner gives you a cross-check. Oil use can be estimated from the nozzle rating and burner run time, which lets you compare a delivery-based figure with the equipment (see related: How to Estimate Oil Use From Nozzle Size and Burner Run Time).
Oil also heats water in many houses. A boiler with a tankless coil or an indirect tank burns oil every day of the year. The summer delivery tells you the baseline.
What changes the reading
Automatic versus will-call delivery. On automatic delivery the dealer predicts use from degree days and a house-specific figure, sometimes called a K-factor (degree days per gallon, or its inverse), and schedules the truck. When equipment changes, the dealer's figure is stale until a few deliveries recalibrate it, so a new furnace can bring an early or a late truck for reasons that have nothing to do with how much fuel it burns.
A new appliance on the same tank. A pool heater, generator, fireplace or dryer added to a propane system adds load the old deliveries never carried.
A shared or second tank. Some properties have a separate tank for a pool heater or an outbuilding. Make sure the tickets you are comparing are for the same tank.
Price, not gallons. If gallons per day held still and the bill rose, the change is in line [2] or line [3]. Compare price per gallon across the tickets before touching anything mechanical.
A leak. A real increase in gallons per day, with weather taken out and no new load, deserves a leak check by the propane supplier or the oil service company before anyone looks at combustion. Propane and oil systems do not show up on a utility meter, so the delivery record is the only record of a slow loss.
Where readers go wrong
Comparing deliveries instead of periods. A delivery is a bucket of fuel that covers however many days elapsed. Without the days, it is not a rate.
Trusting the tank gauge over the truck meter. A float gauge that is off by several percent on a 1,000 gallon tank is off by dozens of gallons.
Mixing propane and oil gallons. A gallon of oil carries about 1.5 times the heat of a gallon of propane. A shop that switched a customer from oil to propane and compares gallon counts will report a fuel-use increase that is mostly unit.
Reading one winter's ticket as a verdict. Two tickets give one comparison. The sibling that builds a full season from a run of tickets is where the stronger answer comes from (see related: How to Estimate Delivered Fuel Use From a Run of Tickets).
References
- See related: Propane Homes: What Every Trade Should Know
- See related: How to Estimate Delivered Fuel Use From a Run of Tickets
- See related: How to Compare Heating Costs Across Fuels per Million BTU
- NFPA 58 (Liquefied Petroleum Gas Code) and NFPA 54 (National Fuel Gas Code), in the editions your state has adopted, which set container filling limits and the leak-check practice after an out-of-gas event
- U.S. Energy Information Administration heat content figures for propane and No. 2 distillate fuel oil