How long does an 11 kg LPG tank actually last?

The honest answer is four to six weeks for a household of four to six people who cook twice a day. But that range is wide enough to be nearly useless when you are trying to decide whether to order now or risk another week, so here is the arithmetic behind it.

Start with the burner, not the tank

A standard domestic LPG burner on full uses roughly 0.2 to 0.3 kg of gas per hour. A small simmer ring is nearer 0.1 kg. So an 11 kg cylinder holds something like 35 to 55 hours of full-power cooking.

Divide that by what you actually do:

If you are in that last row, you are buying the wrong size. A 22 kg cylinder costs less per kilo and halves the number of changeover days where you cannot cook.

Three things that quietly eat your gas

1. Flames licking up the side of the pan. Any flame you can see past the edge of the pot is heating the room, not your food. Turn it down until the flame tips just touch the base. This alone is commonly a 20–30% saving.
2. No lid. Boiling with the lid off can take half again as long. A lid is the cheapest efficiency upgrade in any kitchen.
3. A slow leak. If your tank is emptying noticeably faster than it used to and nothing about your cooking changed, check the hose and the regulator joint with soapy water. A leak too small to smell is still gas you paid for, leaving the building.

How to tell how much is left

Gauges on domestic regulators measure pressure, and LPG pressure stays almost constant until the tank is nearly empty — so the needle sits in the middle and then falls off a cliff. It tells you very little. Two better methods:

Weigh it. Every cylinder has its empty (tare) weight stamped on the collar, usually around 13–14 kg for an 11 kg tank. Put it on a bathroom scale. Current weight minus tare weight is the gas you have left. This is exact.

The warm-water trick. Pour warm water down the side of the tank, then run your hand down it. The metal is cool where there is still liquid gas and warmer above the line. You can feel the level to within a couple of centimetres.

Keep a spare, and order on a day you choose

The real cost of running a tank to empty is not money, it is the evening you cannot cook dinner. A spare 11 kg cylinder sitting in a ventilated spot means you change over when it suits you and order the refill the next morning. Most of our regular customers run two tanks permanently for exactly this reason.

Write the date on the tank with a marker each time you connect one. After two changes you will know your own burn rate better than any table on a website.