Why the term “unit” can be confusing

On many park home sites supplied by bulk LPG tanks, individual homes are fitted with gas meters that do not measure energy directly. Instead, these meters usually record the volume of LPG vapour used.

In practice, this means:

• Residents are often billed a price “per unit”
• But the bill may not clearly state what that unit represents
• This makes it difficult to compare costs with other fuels or suppliers, which are normally quoted in pence per kWh
  

The key assumption used in this example

For illustration purposes, this explanation assumes what is most common on park home LPG systems:

1 unit = 1 cubic metre (m³) of LPG vapour recorded by the gas meter



Important Note:

This assumption only applies if your gas meter actually records usage in cubic metres (m³).

Some older or alternative meters record gas in cubic feet (ft³), which would require different conversion factors. Residents are strongly encouraged to check the front of their meter display to confirm the unit of measurement before relying on any running cost calculations.

How a volume “unit” translates into usable heat (kWh)

Because LPG meters measure volume, conversion factors are needed to estimate how much usable heat that volume represents.

Commonly used industry reference figures for propane are:

• 1 cubic metre (m³) of LPG vapour ≈ 3.85 litres of liquid propane
• 1 litre of propane ≈ 7.08 kilowatt-hours (kWh)

Using these figures:

3.85 litres × 7.08 kWh per litre = 27.26 kWh

This means that, under this assumption:

1 unit (1 m³ of LPG vapour) represents approximately 27.26 kWh of usable heat

Price example (illustrative only)

If a park site operator charges £3.30 per unit, the equivalent energy price can be estimated as follows:

• £3.30 ÷ 27.26 kWh = 12.1 pence per kWh (excluding VAT)

Domestic LPG is subject to VAT at 5%, giving:

• 12.1 p × 1.05 = 12.7 pence per kWh (including VAT)

Quick sense-check summary

Item Illustrative value

• Assumed meter unit 1m³ LPG vapour
• Liquid equivalent 3.85 litres
• Energy content 27.26 kWh
• Example charge £3.30 per unit
• Estimated price per kWh £0.121 excluding Vat
• Estimated price per kWh £0.127 including Vat

What residents are encouraged to do

• Check your gas meter to confirm whether it measures usage in m³ or ft³
• Ask the site operator to confirm in writing what a “unit” represents
• Ask what conversion factors are used between tank deliveries and resident billing
• Use kWh comparisons to better understand relative costs

This overview is intended to help residents ask informed questions and better understand their gas bills. Actual charges may vary depending on meter type, conversion methods, tariff structure, and VAT treatment.

Additional Charges

Park site operators frequently include a "Meter reading charge" on gas bills. Like standing charges for natural gas and electricty, this additional cost is excluded from our cost comparison calculations, as it isn't directly related to the amount of useable heat produced by boiler systems.