How long does a 20-pound propane tank last?

A 20-pound propane tank holds roughly 430,000 BTUs of energy. A two-burner camp stove running one burner at medium heat burns about 7,000 BTUs per hour, giving roughly 60 hours of cooking time from a single tank. A 30,000 BTU indoor propane heater running continuously would drain the same tank in about 14 hours. Actual runtime depends entirely on the BTU rating of your appliance and how hard you run it.

Can I store propane tanks in my garage or basement?

No. Propane tanks must be stored outdoors in a well-ventilated area away from heat sources and ignition points. Never store propane cylinders indoors, in a basement, in an attached garage, or in any enclosed space. Propane is heavier than air and will accumulate at floor level if a small leak occurs — a spark can ignite the accumulation. Store tanks upright on a flat surface at least five feet from any structure entry point.

How do I know if my propane tank has a leak?

Propane is odorless but suppliers add ethyl mercaptan, which smells like rotten eggs or sulfur. If you smell this near a tank or appliance, turn off the supply valve immediately, leave the area, and call your supplier or emergency services from outside. To test connections and hoses, apply soapy water — bubbles indicate a leak. Never test with an open flame.

What size propane tank do I need for whole-home backup?

A 120-gallon tank provides a meaningful emergency reserve for cooking and supplemental heating. A 250-gallon tank supports a whole-home propane backup heating system through a typical winter outage of several weeks. For permanent whole-home heating as a primary or backup system, 500 gallons is the common residential minimum. Tank size depends heavily on the BTU load of your appliances and how many days of autonomy you need.

Propane Basics — New World Survival

WHY IT MATTERS

Propane stores indefinitely. Nothing else quite does.

Gasoline degrades in 30–60 days without stabilizer. Diesel fares better but still degrades. Propane has no shelf life — a tank filled today is as good in five years as it is now. For long-term backup energy storage, that's a meaningful advantage.

Indefinite shelf life

Propane doesn't degrade, gum carburetors, or lose energy density over time. A tank stored properly five years ago burns identically to one filled last week.

Works in cold weather

Propane vaporizes at -44°F, so it functions in nearly any winter condition. Gasoline cold-starts are unreliable; propane appliances and generators start reliably at temperatures where gas balks.

Broad appliance support

Cooking stoves, space heaters, water heaters, whole-home furnaces, clothes dryers, and dual-fuel generators all run on propane. One fuel, many uses.

TANK SIZES

The right tank for the job.

Propane tanks come in five practical sizes for household use. The right size depends on what you're powering and how much autonomy you need.

20 LB · ~430,000 BTU

Grill tank

The standard portable cylinder used for gas grills and camp stoves. Holds about 4.7 gallons. Widely available for exchange at hardware stores and gas stations.

Best for: camp stoves, portable heaters, small grills. Easy to transport and exchange.

100 LB · ~2.16M BTU

Portable backup tank

Holds about 23 gallons. Too heavy to carry when full (about 170 lbs) but can be moved on a hand truck. Typically used for generator backup and supplemental heating.

Best for: backup generator fuel, outdoor heaters, patio use. Filled by a propane supplier truck.

120 GAL · ~10.5M BTU

Residential starter

The smallest permanently installed residential tank. Provides meaningful backup capacity for cooking, water heating, and supplemental heat. Typically above-ground installation.

Best for: cooking backup, water heating, or a dedicated generator supply.

250 GAL · ~21.5M BTU

Whole-home backup

Supports a whole-home backup heating system through a multi-week winter outage when paired with an efficient propane furnace. Common size for homes in cold climates using propane as a secondary heat source.

Best for: backup whole-home heating plus cooking and water heating.

500 GAL · ~43M BTU

Primary heating tank

The standard minimum for homes using propane as their primary heating fuel. Typically filled once or twice per season. Requires a setback from structures per local fire code.

Best for: primary whole-home heating. Above or below ground installation available.

Tanks 120 gallons and larger are typically leased from and filled by a propane supplier, not purchased outright. Ask about lease terms, delivery schedules, and automatic fill programs before committing to a supplier.

HOW LONG IT LASTS

The BTU math. Two minutes to your answer.

Every propane appliance has a BTU rating. Every gallon of propane contains 91,502 BTUs. Divide the tank's total BTUs by the appliance's BTU rating to get hours of runtime.

THE FORMULA

Tank gallons × 91,502

= total BTUs in tank

Total BTUs ÷ Appliance BTU/hr

= hours of runtime

Tanks are filled to 80% capacity (never 100%) — a "20 lb" cylinder holds 4.7 gallons, not the full theoretical volume. Actual runtimes are 10–20% lower than calculated due to efficiency losses.

RUNTIME REFERENCE · 20-LB TANK (4.7 GAL · ~430,000 BTU)

ApplianceBTU/hrRuntime

Camp stove (1 burner, medium) 7,000 ~60 hrs

Mr. Heater Buddy (indoor heater) 9,000 ~48 hrs

Gas grill (two burners, medium) 24,000 ~18 hrs

Portable generator (dual fuel) 35,000 ~12 hrs

Propane patio heater (outdoor) 46,000 ~9 hrs

Runtime estimates at continuous rated output. Real usage with cycling and partial output extends actual runtime.

Affiliate disclosure: New World Survival earns a small commission on purchases made through links on this page, at no cost to you. We only recommend gear we'd put in our own kit.

STORAGE AND SAFETY

Store it right. Know the smell.

Propane is safe when handled correctly. These are the rules that matter.

Storage rules

Never store cylinders indoors, in a basement, or in an attached garage
Never store near a heat source, open flame, or electrical panel
Store upright on a flat, stable surface outdoors
Keep at least five feet from any door, window, or structure entry
Keep the valve cap on when not connected
Inspect cylinders for rust, dents, and damaged valves before use
Cylinders have a 12-year inspection date stamped on the collar — check before refilling

Leak detection

Propane is odorless. Suppliers add ethyl mercaptan — a sulfur compound that smells like rotten eggs — so leaks are detectable. If you smell it near a tank, appliance, or supply line:

Turn off the supply valve immediately
Do not operate any switches, lights, or devices
Leave the building and move upwind
Call your supplier or 911 from a safe distance
Do not re-enter until cleared by a professional

To test connections without a flame: brush soapy water on hose connections and the regulator. Bubbles indicate a leak. Tighten the connection and retest. Replace any hose that leaks at the hose itself rather than a connection point.

Outdoor appliances stay outdoors

Propane patio heaters, outdoor grills, and turkey fryers are not rated for indoor use and produce CO at levels that accumulate to dangerous concentrations indoors. The indoor-rated heaters — Mr. Heater Buddy series and similar ODS-equipped models — are a different product. See the Heating During Outages guide for safe indoor heating options.

RELATED GUIDES

Propane basics. Stored energy on your terms.