Gas Holder
A vessel used to store gas.

Gas Point Registration Number (GPRN)
A unique 7 digit identification number (it may appear to have less if it starts with one or more zeros) allocated to a gas meter at a business or domestic supply point.

Gas Point Registration Operator (GPRO)
The GPRO works on an independent basis to manage the register of all natural gas points across the country. The office will supply details of the annual usage of a GPRN.

Gas Substation
A pressure reduction station located on customers premises where gas is reduced from mains pressure regulated at a medium or low pressure for domestic or industrial use.

Gas Transporter (GT)
Responsible for maintaining a gas supply network. They may also be requested by the Supplier via the Shipper to provide a meter for the consumers usage. Requires a GT licence.

Gas-fired Generation
Around one third of the UK and Ireland's electricity is currently produced by gas-fired power stations. Combined Cycle Gas Turbine (CCGTs) are currently the more favoured option for new large-scale electricity generation compared to new coal power stations. Burning natural gas to produce electricity does emit carbon dioxide, but the emissions are significantly lower than from coal. However, the availability of gas and the cost is likely to be unpredictable so there could be a risk that when you need the electricity there may not be enough available, or that relying solely on gas fired generation will lead to increases in your energy bills.

Breakdown of hydrocarbons into a syngas by carefully controlling the amount of oxygen present.

An intermediate distillate product used for diesel fuel, heating fuel and sometimes as feedstock.

Gate closure
Three and a half hours before the start of a settlement period, it defines the moment when bilateral contracting ends and the 'Balancing Mechanism' for a trading period begins.

This covers the production of electricity at power stations. At present the main fuels used are gas, nuclear and coal, although there is now a growing use of renewable forms of energy, such as wind power, the burning of gas from landfill and waste incineration.

A machine that converts mechanical energy into electricity.

Gigawatt (GW)
A unit of power equal to 1 billion watts; 1 million kilowatts, or 1,000 megawatts.

Gigawatt-hour (GWh)
The volume of energy supplied at a rate of one GW for the duration of one hour.

Global Warming
The gradual increase in the average temperature of the Earth's surface and atmosphere. The majority of scientists agree that the current warming we are experiencing is caused by the release of greenhouse gases from the burning of fossil fuels and other industrial processes.

GPRS - General Packet Radio Service
Mobile data service available to all users of the cellular communication systems global system for mobile communications.

Green Certificates
An official record proving that a specified amount of green electricity has been generated. Green certificates represent the environmental value of renewable energy production. The certificates can be traded separately from the energy produced.

Greenhouse Effect
The way gases in the earth's atmosphere trap heat. The build up of these gases, especially carbon dioxide, are thought to cause global warming.

Greenhouse Gas (GHG)
A gas that absorbs infra-red radiation (i.e. the suns heat and energy) in the atmosphere. Greenhouse gases include water vapour, carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), halogenated fluorocarbons (HCFCs), ozone (O3), perfluorinated carbons (PFCs), and hydrofluorocarbons (HFCs). These gases contribute to the 'greenhouse effect'.

Greenhouse Gas (GHG) Protocol
A widely used standard for emissions reporting. The protocol covers project emissions reporting and corporate emissions reporting. The corporate emissions reporting standard provides a methodology for calculation of a carbon footprint. The protocol was developed by the World Resources Institute and the World Business Council for Sustainable Development.

Greenwich Mean Time/Clock (GMT)
Some suppliers base their day/night split on GMT, others on clock times. The difference can be significant for consumers with plant operating at or near the cross-over period.

Grid Supply Point (GSP)
The GSP is the point at which energy is taken from the National Grid transmission system into a local distribution system.

Ground Source Heat Pump (GSHP)
A type of heat pump that uses the natural heat storage ability of the earth and/or the groundwater to heat and/or cool a building.

GSM - Global System for Mobile Communications
The most popular standard for mobile telephony systems in the world. Commonly used for transmitting data from advanced and Smart meters.