When to Reorder Propane — The 20–30% Rule and How to Plan Ahead

The 20–30% Rule

The most widely cited guideline in the residential propane industry is to call for a delivery when your tank gauge reaches 20–30%. This recommendation comes from major propane suppliers, industry associations, and the Propane Education and Research Council (PERC).

The reasoning behind this threshold is twofold:

1. Safety buffer: It keeps you from ever running out of propane between the time you call and when the truck arrives. Even if delivery takes a week, you have enough propane to continue using your appliances.
2. Avoid empty tank consequences: If a fixed propane tank runs completely empty, your supplier is required to perform a pressure test and leak check before refilling. This delays your delivery and costs you money. The 20–30% threshold is designed to prevent this from happening.

Why Running Out of Propane Is Worse Than Just Being Inconvenient

Many homeowners have the idea that running out of propane is roughly equivalent to running out of gas in a car — you call, they come, they fill it up, done. This is not how it works for fixed residential tanks.

When a fixed propane tank runs completely empty, propane safety regulations require the supplier to perform a pressure test before refilling. This test checks that the entire fuel system (regulator, pipes, valves, and appliances) is intact and leak-free after having been depressurized. Here's what that means in practice:

• A technician must visit your property — which requires scheduling, often 1–3 days out
• The pressure test typically costs $50–$150 and is the customer's responsibility
• If a problem is found, repairs must be completed before propane is restored
• You have no heat, no hot water, and no cooking until the process is complete

In winter, this can be genuinely dangerous for vulnerable household members and livestock. Even in mild weather, it's a significant disruption. The 20–30% reorder threshold exists specifically to avoid this scenario.

Understanding Propane Delivery Lead Times

Propane delivery is not like ordering something online that arrives the next day. Delivery schedules vary by supplier, season, and location:

Normal conditions

Most residential propane suppliers can deliver within 3–5 business days of a request. If you call at 25% in September with moderate usage, you will almost certainly receive your delivery before hitting 10%.

Winter peak demand

During the heating season — particularly following a cold snap when many customers order simultaneously — delivery times can stretch to 7–14 days with some suppliers. This is the most common scenario in which people accidentally run out: they waited until 15–20% and then couldn't get a delivery before running dry.

Remote or rural properties

Propane trucks follow routing schedules. If you live or own a property in a rural area, your supplier may only run deliveries to your area on specific days of the week. Combined with normal lead time, this can mean your first available delivery slot is 10+ days out. For remote properties, a 40% reorder threshold is a more prudent standard.

Automatic delivery programs

Many propane suppliers offer automatic delivery programs where they monitor your usage (based on degree-day calculations or tank monitors) and schedule deliveries proactively. If you're enrolled in automatic delivery, you don't need to call — but you should still keep an eye on your level and know your supplier's policies. PropanePal is useful even with automatic delivery, as it gives you an independent record of deliveries and spending.

Adjusting Your Reorder Threshold for Your Situation

The 20–30% standard is a good starting point, but you may want to adjust based on your specific circumstances:

• Primary residence in cold climate, propane heating: Use 30% or higher. Your daily usage in winter is high; any delivery delay hits hard.
• Seasonal cabin or vacation property: Use 40%. Delivery to remote properties often takes longer, and you may not be present to monitor the situation if the weather turns unexpectedly cold.
• RV or portable cylinders: Use 25–30%. When you're on the road, propane refills are convenient and frequent — but plan ahead before setting off on a long trip.
• Grill use only, warmer climate: 20% is fine. Low usage and no heating risk.
• Generator tank: Keep it well above 30% year-round. You need propane to be available at any moment, not just when it's convenient to order.

How to Calculate When You'll Hit 20–30%

Knowing when to call is different from knowing today you're at 30%. Ideally, you want to anticipate the 20–30% threshold and call before you get there.

The formula is straightforward:

Days until 20% = (current gallons − gallons at 20%) ÷ daily usage rate

For example: A 500-gallon tank at 55% has 275 gallons. At 20%, it has 100 gallons. The difference is 175 gallons. If you're using 2.5 gallons per day, you'll hit 20% in 175 ÷ 2.5 = 70 days.

This calculation is exactly what PropanePal does automatically. Log your gauge reading, and PropanePal shows you the number of days until your reorder threshold and the specific recommended order date — updated every time you log a new reading.

Pre-Season Fill Planning

One of the smartest moves a homeowner can make is scheduling a propane fill in October — before the heating season begins in earnest. Here's why:

• Propane prices tend to be lower in fall before winter heating demand peaks
• Delivery windows are wider in fall when suppliers are less busy
• You start heating season with a full tank, maximizing your buffer
• You avoid scrambling for delivery during the first serious cold snap of the year

PropanePal tracks your usage from previous years. After one heating season of logging, you can use your historical fall-to-spring consumption to estimate how much propane to request for your pre-season fill.