Home / Heat and cooking

20 lb propane tank: what to check, how long it lasts, where it lives

By the Plain Prepper editors. Updated 2026-10-15.

We research products from makers' specs, manuals and safety agencies; we do not run hands-on tests. Links to Amazon may earn us a commission at no cost to you. How this works.

Quick answer

The 20 lb tank is the standard grill cylinder, and it doubles as outage fuel for a grill, camp stove or an approved heater on a hose. An exchange tank from AmeriGas holds 15 lb of propane, not 20. Before any fill, the tank needs an OPD valve and a valid date: PHMSA says requalify within 12 years of manufacture. Mr. Heater's Portable Buddy manual lists up to 48 to 110 hours on a 20 lb cylinder. Store it outside, upright and away from heat, never in a garage or basement.

What a 20 lb tank is and what it weighs

AmeriGas calls the 20 lb cylinder the standard propane grill tank, and says most mid-sized grills use one. The 20 lb figure is not the weight of the empty tank. Flame King's specs show what the steel itself weighs:

Flame King model	Build	Empty weight	Size	Extra
YSN201	Welded steel, powder-coated	18 lb	12.3 x 12.3 x 17.8 in	OPD valve
YSN230	Welded steel, powder-coated	20 lb	13 x 13 x 18 in	OPD valve and built-in gauge

A steel YSN201 holding 20 lb of propane would weigh about 38 lb (18 + 20), so plan on lifting that much. Flame King ships both empty and pre-purged, ready for a first fill, and lists them as DOT and Transport Canada certified after X-ray and hydrostatic testing.

Exchange or refill

Exchange is the quick option. AmeriGas says most retail locations offer grill tanks for sale and exchange, it accepts all brands for exchange, and some retailers can refill your tank instead. Two facts from AmeriGas shape the choice:

• Fill amount. AmeriGas grill tanks contain a net weight of 15 lb of propane. That is three quarters of a 20 lb tank's rating.
• Date handled for you. AmeriGas says tanks from a certified AmeriGas exchange retailer have already been recertified.

Refilling keeps the tank you own, including a gauge model you chose on purpose. Ask the refill location how much propane it puts in before you compare. For outage planning, what matters is pounds of propane on hand, so count exchange tanks at 15 lb each.

Check the valve and the dates before a fill

OPD valve. The propane industry's safety booklet says only to use cylinders with an Overfill Prevention Device, a safety feature required by law. Most have a triangular handwheel marked "OPD." If yours lacks one or you are unsure, exchange it or buy a new cylinder.

Condition. PHMSA says not to fill any cylinder with:

• Excessive rust, corrosion or pitting, particularly near the bottom
• Dents, bulges, cuts or cracks
• A missing or damaged foot ring, collar or valve cover
• A leaking or defective valve or pressure relief device

Dates. The manufacture date is stamped in the collar. PHMSA says cylinders must be requalified within 12 years of manufacture. After that, read the requalification stamp:

Mark after the date	Method	Next requalification
No letter	Volumetric expansion test	Within 12 years
S	Proof pressure test	Within 10 years
E	Visual inspection only	Within 5 years

PHMSA's example "0422 E" means a visual requalification in April 2022, due again by April 2027.

How long a 20 lb tank lasts

Two published figures give a starting point:

• Heater: Mr. Heater's Portable Buddy (MH9BX) manual lists up to 48 to 110 hours on a 20 lb cylinder, from the 9,000 BTU High setting to the 4,000 BTU Low setting.
• Grill: AmeriGas says a 20 lb tank should typically last about 15 hours on a standard mid-sized grill.

If you run an exchange tank holding 15 lb, scale the heater figure by 15/20. That is an estimate of about 36 to 82 hours (48 x 0.75 and 110 x 0.75). The manual also warns that run times drop significantly when operating continuously below 20°F. Never warm a cold tank with a heater or flame; the safety booklet forbids applying an external heat source.

For a multi-day outage, count tanks rather than guessing. Two full tanks on a Buddy at Low cover far more hours than one tank at High, so heat one room and dress warmly.

Storing and moving the tank

The safety booklet's storage rules are short:

• Keep cylinders outside, upright and away from ignition and heat sources. They are designed to sit outside in any weather, even full sun.
• Never use or store one in a basement, garage, shed or tent. Even an "empty" cylinder may hold enough propane to be hazardous.
• Do not keep a spare cylinder under or near a grill or other propane appliance.
• Keep the valve closed when the tank is not connected or not in use. Turn the cylinder valve off before floodwater rises.

For transport, secure the tank upright so it cannot roll, keep it out of the passenger area, drive straight to your destination and take it out right away. U.S. limits in a closed vehicle are no more than four 20 lb cylinders and no more than 90 lb of propane in total. AmeriGas adds: close the valve and use a plug if required, and never leave a filled tank in a hot vehicle.

Leaks, heater hoses and disposal

Do a bubble test at the start of each season and every time you connect: apply thick soapy water or leak detector solution on the valve and connection, open the valve slowly and watch. If bubbles persist after tightening, close the valve and call your propane retailer. If you smell gas, close the valve only if there are no flames or visible cloud of propane, leave the area and call 911.

The Buddy manual allows a 20 lb remote cylinder only when the cylinder stays outdoors, connected through Mr. Heater's listed hoses. Its F273704 Buddy series hose needs no fuel filter; the other listed hoses need filter F273699, replaced yearly. The manual is blunt: never bring a refillable propane cylinder indoors.

Never repair or modify a cylinder, and never use one that has been in a fire. Do not put old tanks in the trash. AmeriGas says exchanging is the easiest way to dispose of one, and most refill or exchange locations take unwanted tanks.

What to look for when you buy

Questions people ask

How much propane is in a 20 lb exchange tank?

AmeriGas says its exchange grill tanks contain a net weight of 15 lb of propane. A refill location may put in a different amount, so ask before you compare.

How long does a 20 lb propane tank last on a heater?

Mr. Heater's Portable Buddy manual lists up to 48 to 110 hours on a 20 lb cylinder, depending on the High or Low setting. Expect less below 20°F and less from a 15 lb exchange fill.

When does a 20 lb propane tank expire?

PHMSA says a cylinder must be requalified within 12 years of its manufacture date. After that, the stamp letter sets the next interval: 12 years with no letter, 10 years for S, 5 years for E.

Can I store a 20 lb propane tank in the garage?

No. The propane industry's safety booklet says never to use or store cylinders in a basement, garage, shed or tent. Keep them outside, upright and away from heat.

Sources

• Is Your Cylinder Safe to Fill? PHH50-0201-0323, Pipeline and Hazardous Materials Safety Administration
• Propane safety booklet PRC-101063D: portable cylinders, transport and storage, Propane Education and Research Council
• Grill tanks FAQ: tank size, net fill and grill runtime, AmeriGas
• Buy, exchange or dispose of a propane tank, AmeriGas
• Propane tank recertification, AmeriGas
• Portable Buddy MH9BX owner's manual: 20 lb runtime and remote cylinder rules, Mr. Heater (hosted by Lowe's)
• 20 lb LP cylinder with OPD, YSN201, Flame King
• 20 lb LP cylinder with OPD and gauge, YSN230, Flame King

Sources checked 2026-10-15.