Liquefied petroleum gas, universally known as LPG, is a group of hydrocarbon gases, primarily propane and butane, that are gaseous at normal atmospheric pressure and temperature but liquefy under moderate pressure, allowing large volumes to be stored and transported in relatively compact cylinders or tanks. LPG is an important fuel for the approximately two million UK homes that are not connected to the mains natural gas network.

Propane vs Butane

The two main LPG gases are propane (C3H8) and butane (C4H10). Propane has a lower boiling point of minus 42 degrees Celsius, meaning it vaporises reliably down to very cold temperatures and is suitable for outdoor use and year-round applications in the UK climate. Butane has a higher boiling point of minus 2 degrees Celsius, which means it does not vaporise well in cold weather and is unsuitable for outdoor cylinders in winter. For this reason, propane is generally used for central heating and hot water applications, while butane is used for portable gas appliances and patio heaters in warmer conditions.

How LPG Is Supplied

LPG is supplied in portable cylinders in various sizes, from the small cartridge used in camping stoves to the large 47kg commercial cylinders used for heating. For properties with significant LPG use, a larger bulk tank installed on the property is more cost-effective and convenient than exchanging cylinders. Bulk tanks are typically owned or leased from the LPG supplier, who delivers fuel by tanker. The tank size is calculated from the property's annual consumption.

LPG for Home Heating

LPG central heating works in the same way as natural gas central heating, using a boiler that burns the gas to heat water for radiators and domestic hot water. LPG boilers are available from the same manufacturers as natural gas boilers and achieve similar efficiency ratings. The main difference is cost per unit of energy: LPG is typically more expensive per kWh than natural gas but significantly cheaper than direct electricity, making it a viable alternative to oil heating in off-grid locations.

Summary

LPG is a mixture of propane and butane stored under pressure in cylinders or bulk tanks. Propane is suitable for year-round outdoor use; butane is not suitable in cold weather. LPG provides central heating, hot water, and cooking fuel for off-grid properties. It is more expensive per unit than natural gas but cheaper than direct electricity. LPG is heavier than air and pools at low levels on leaking; detectors must be positioned accordingly.