Jargon buster

Our quick guide to some of the terminology you may encounter in the energy sector.

See below for explanations of common energy industry terminology.

Annual Quantity

The annual quantity of gas consumed.


British Thermal units, the amount of therms a piece of equipment would use in a specified time. This is used to work out daily, weekly and annual consumption and is used to work out an estimated Annual Quantity for a customer installing new equipment.

Bulk Bill

This is a bill which is comprised of invoices that relate to more than one account, and is always sent to Head Office. Also referred to as a consolidated bill.

Calorific value (CV)

This is a measure of the energy contained in gas. It represents the amount of heat released as the gas is burned.


Climate Change Levy. This is a Levy (tax) introduced by the Government on 1st April 2001 on the use of energy in industry, commerce and the public sector.

Day Ahead Market

The market for energy 24 hours in advance of a given time in any day.


Distribution Network Operator. A company that owns & maintains a network for transporting electricity.


Estimated Annual Consumption. An estimate of your forecast annual consumption provided by your data collector, based on historical meter reads.

Erroneous Transfers (ET's)

This is a process that is undertaken when a site is registered to a new supplier incorrectly. Agreement is obtained from the previous supplier to transfer back to them.

Fire Account Number

An account number which will appear on your invoice.

First and Next units (previously called Primary and Secondary units)

Bills are calculated using two different pricing bands: primary and secondary. The threshold at which you switch from primary to secondary prices depends on the tariff. To calculate the Primary (First) unit price the threshold limit is divided by 365 days and multiplied by the number of days the bill is for. Everything after that is charged at the Secondary (Next) rate.


Gigawatt. One billion watts. One million kilowatts. One thousand megawatts.

Hundreds of cubic feet (hcf)

Imperial meters measure the gas consumed by your home in hundreds of cubic feet. One unit represents the amount of gas needed to fill 100 cubic feet. 

How do we convert this into kilowatt-hours?

We have a licence requirement to bill you in kilowatt-hours for the gas you use (kWh).

All the figures we use to convert your gas usage into kWh can be found underneath your gas meter readings on your bill.

Here's how we do it:

For imperial meters: Take the volume used, shown with 'hcf' on the front of your bill and multiply this figure by 2.83 to convert to cubic metres (m³). Follow step 2 onwards.
For metric meters: Take the volume used, shown with 'm³' on the front of your bill.

Multiply this figure by the conversion factor of 1.02264, then by the calorific value shown on your bill underneath your meter readings.

Finally divide this figure by 3.6 to show your usage in kWh.

MPR (Meter Point Reference)

This is your unique gas Meter Point Reference number, and is used to identify your gas supply. Your MPR is on your gas bill, not on the meter itself.


Meter Serial Number. A number given to identify an actual meter.


Office of Gas & Electricity Markets. Regulator for gas & electricity businesses in Great Britain.


Supply Start Date


An imperial term that measures the volume of gas. KWh has replaced this. 1 Therm = 29. 3071 kWh