Home heating fuel is one of the few purchases where the price you pay depends almost entirely on when you buy. Heating oil and propane swing with global markets, seasonal demand, and weather forecasts, and the gap between a summer fill and a January fill can reach a dollar or more per gallon. Pre-buying attacks that volatility: you pay a set price in the off-season for fuel delivered through the winter. The same propane that fills residential tanks also powers equipment across construction rental fleets, so the buying mechanics are familiar to anyone who manages fuel at scale.
The 2008 season showed why timing matters. Retail heating oil climbed from roughly $3.00 a gallon in January to more than $4.70 by July, and propane followed with a spike above $3.20 before both collapsed later that year. Homeowners who locked prices in summer paid materially less than those who bought at the peak.
How Pre-Buy Contracts Work
A pre-buy contract is simple in shape: in spring or summer you agree to buy a set number of gallons at a fixed price, pay up front or in installments, and the supplier delivers those gallons when you call through the winter. You are effectively hedging the price risk yourself, betting that winter prices will exceed your locked rate.
Three contract types
- Fixed-price pre-buy: locks both the price and the volume of fuel you purchase.
- Capped price plan: you buy at the market rate when it sits below the cap and pay the cap when the market runs above it.
- Budget plan: no price lock at all; your estimated annual cost is averaged into equal monthly payments and settled at year end.
Fixed-price pre-buys suit homeowners who want certainty. Capped plans suit those who expect mild winters. Budget plans solve cash flow, not price, and carry a year-end bill that can surprise you.
What the fine print actually says
- Gallons covered: pre-buys often cap at a set volume, with market price for anything beyond.
- Delivery minimums: most suppliers require a minimum drop of 100 to 150 gallons for oil or a full tank for propane.
- Expiration: unused pre-bought gallons typically expire at the end of the season or roll over at the supplier’s discretion.
- Refundability: some contracts refund unused balances, others do not, and cancellation fees vary.
- Credit requirement: paying up front for 500 gallons at $3.50 ties up $1,750 before winter.
Running the savings math
A simple example shows the scale. A home that burns 900 gallons of heating oil in a winter saves $0.50 per gallon when the pre-buy price beats the winter market, which is $450 for the season. The same math applies to propane: 800 gallons at a $0.40 spread is $320.
Pre-buy is one way to manage energy cost, but it is not the only lever. The same fuel-versus-electricity calculus that drives propane autogas versus battery-electric decisions in commercial fleets applies at home when you compare a new furnace against a heat pump, and the choice of energy source can matter more than the timing of the purchase.
Heating Oil vs Propane: Fuel Facts That Matter
The two fuels are not interchangeable, and the numbers explain why. A gallon of #2 heating oil contains about 138,500 BTUs; a gallon of propane contains about 91,500 BTUs. Propane burns cleaner and lets furnaces reach 90 to 98 percent AFUE efficiency, while oil equipment typically runs 80 to 90 percent. After efficiency, the cost per useful BTU often lands closer than the raw prices suggest.
| Fuel | Energy per gallon | Typical appliance efficiency | Cost per million BTU | Delivery |
|---|---|---|---|---|
| Heating oil (#2) | 138,500 BTU | 80-90% AFUE | $28 to $36 at $3.50 to $4.50 per gallon | Tank truck; on-site storage |
| Propane | 91,500 BTU | 90-98% AFUE | $27 to $33 at $2.50 to $3.00 per gallon | Tank truck; on-site storage |
| Natural gas | 1,037 BTU per cubic foot | 90-96% AFUE | $15 to $20 per million BTU | Pipeline; no storage |
| Electric resistance | 3,412 BTU per kWh | About 100% at point of use | $38 to $48 at $0.13 to $0.16 per kWh | Grid |
| Heat pump | 3,412 BTU per kWh | 250 to 350% seasonal efficiency | $12 to $19 at $0.13 to $0.16 per kWh | Grid |
The example prices are illustrative; local rates change the ranking. What holds across regions is that natural gas and heat pumps usually beat oil and propane on cost per delivered BTU, while oil and propane win on independence from pipelines and the grid.
The electrification alternative
For some households the answer is to leave both fuels behind. The argument to stop using propane and oil and go electric is laid out in detail by Green Building Advisor, and the math improves as heat pump efficiencies rise and electricity prices hold steady. Where that switch is not practical, pre-buy remains the main tool for controlling the fuel bill you still have.
Efficiency and Maintenance: Protecting Your Fuel Investment
Pre-buying locks the price of the fuel; maintenance locks how much of it becomes heat. An oil burner running with a dirty nozzle or a propane furnace with a sooted heat exchanger can waste 10 to 20 percent of the fuel it burns, which quietly erases the savings from a good pre-buy price.
A fall tune-up checklist
- Replace or clean the oil filter and nozzle.
- Check burner electrode settings and flame color.
- Verify carbon monoxide levels in the flue; readings above 100 ppm need attention.
- Test the pressure regulator and gas line connections on propane equipment.
- Inspect the heat exchanger for cracks and corrosion.
- Confirm the thermostat and zone valves cycle correctly.
Waste math example
A 10 percent efficiency loss on an 800-gallon propane season wastes 80 gallons, worth $200 to $260 at typical winter prices. A tune-up that costs $150 to $300 pays for itself in a single season when it recovers even half of that loss.
Suppliers and service companies sell annual contracts that bundle these checks, and a propane heater service performed once a year keeps efficiency and safety in line. The same cadence applies to oil boilers, where a summer service call is cheaper than a January breakdown.
Tanks, Delivery, and Backup Power
Storage shapes the buying decision. Propane arrives by truck into a tank you rent or own; the standard residential sizes are 120, 250, and 500 gallons, and the supplier fills to 80 percent capacity. Heating oil stores in a 275-gallon tank, usually in the basement or buried outside. Tank ownership matters: owned tanks open the market to any supplier, while rented tanks tie you to the leasing company’s prices.
Delivery logistics
Most propane suppliers use a will-call system where you request fills, or an automatic system that monitors usage and schedules drops. Will-call customers who let a tank run low pay for emergency deliveries and can find themselves on a wait list in a cold snap. Oil dealers run similar routes, so a low tank in January means paying whatever the spot market charges.
Generators and the shared tank
Propane’s role extends past the furnace. The same tank can feed a water heater, a cooktop, a fireplace, and a backup generator, and dual-fuel generators that run on gas or propane give homeowners a second use for the stored fuel. Sizing a generator against the tank, rather than buying whichever model is on sale, keeps the whole system coherent.
Estimating Fuel Use and Sizing Your Purchase
A pre-buy contract only pays off if the volume matches reality. Under-buy and you pay market rates for the overflow; over-buy and you tie up cash in gallons you never burn. Two numbers drive the estimate: the size of the heated space and the local climate measured in heating degree days.
A practical estimating method
- Pull your last three years of delivery records; history is the most reliable predictor.
- Adjust for efficiency upgrades, such as a new furnace, by scaling the history.
- Compare against regional norms: a home in a cold climate burns 700 to 1,200 gallons of heating oil or 800 to 1,500 gallons of propane per season.
- Add buffer for hot water and appliances that share the fuel.
- Size the contract at 80 to 90 percent of the estimate and top up at market price if winter runs long.
Generator consumption math
| Generator load | Propane use per hour | Hours per 200 usable gallons |
|---|---|---|
| 5 kW at half load | 1.0 to 1.3 gallons | 154 to 200 hours |
| 7.5 kW at half load | 1.5 to 1.8 gallons | 111 to 133 hours |
| 10 kW at half load | 2.0 to 2.5 gallons | 80 to 100 hours |
Generators are a common reason propane use runs over the heating estimate, and knowing how much propane a generator uses at various loads lets you budget the tank against both heat and power. Running a 7.5 kW generator at half load for eight hours a night during an outage burns roughly 12 to 14 gallons, a real line item on any winter fuel plan.
Combine the two tables and the picture sharpens: a 250-gallon tank that is 80 percent full holds 200 usable gallons, which covers about a week of continuous generator run time at a 5 kW load, before a single degree of heating.
Natural Gas, Electric, or Pre-Buy Oil and Propane?
The pre-buy decision sits inside a bigger question: which fuel should heat the house at all. Natural gas, where a pipeline is available, usually delivers the lowest cost per BTU with no tank and no pre-buy, but it comes with connection fees and no price hedge against a cold winter. Electricity has no fuel delivery at all but costs more per BTU except with heat pumps.
Running the comparison with local rates
The full comparison of natural gas versus propane, including energy output, cost, and safety, is worth running with your actual local rates before signing any pre-buy. Locking a price on the wrong fuel is still locking in the wrong price.
A final decision sequence
- Compare the delivered cost per million BTU for every fuel available at your address.
- Factor in equipment age; a failing furnace changes the fuel decision entirely.
- Check tank ownership and delivery terms before committing to a supplier.
- Read the pre-buy contract for volume caps, expiration, and refund rules.
- Lock only the gallons you expect to burn and keep a small cash reserve for the overflow.
For homes that stay on oil or propane, pre-buying remains a solid, low-effort hedge. Combine a mid-summer price lock with a tuned-up furnace, a realistic gallon estimate, and a tank that is owned or competitively priced, and the winter fuel bill becomes one of the more predictable expenses of the year.