Electrical power that does useful work, typically 95% to 100% of the apparent power. Measured in kW. See also reactive power.

Funding aimed at the reduction of greenhouse gas emissions and the removal of greenhouse gases from the atmosphere and oceans. See also mitigation finance.

A reduction in CO2e emissions, or the removal of CO2e from the atmosphere, that would not otherwise have occurred without a given project or change. See also baseline.

The maximum amount of apparent power that a DNO guarantees for any site with a Half Hourly Meter, measured in kVA. Also known as Availability, Agreed Supply Capacity, Authorised Service Capacity or kVA level.

Alternatives to traditional fossil fuels, including hydrogen, stored electricity and bio-fuels.

A unit of electrical current, commonly shortened to amp.

A meter which automatically collects consumption data and sends it to the supplier to ensure correct bills. See also smart meter and automatic monitoring & targeting.

AD. The breakdown of organic matter, by bacteria, in the absence of oxygen. This produces biogas.

The total power capacity required to operate an electrical system, and thus what a grid must be designed for. It is the square root of the sum of the squares of active power and reactive power.

Annual Quantity, the expected volume of gas consumption at a site, or via a specific meter, over one year.

An underground layer of rock, sand or gravel containing groundwater. Water emerges naturally from an aquifer at a spring, or can be extracted via a well or borehole.

The IPCC Sixth Assessment Report, published in 2023, which provides the IPCC's latest estimates of Global Warming Potential, and thus CO2e.

An SFDR standard for investments that promote environmental or social characteristics alongside other objectives. Such investments are often called 'light green'.

An SFDR standard for investments with an objective relating to sustainable investment and/or carbon emissions reduction. Such investments are often called 'dark green'.

AMT. Systems or equipment designed to automatically measure energy consumption and analyse that data to improve energy efficiency. System elements might include smart meters, sub-meters and software.

A gas or electricity bill that corrects previous undercharging. There are limits on how far back the supplier can go.

Where the futures price for a commodity is lower than the spot price. This is normal for perishable commodities, e.g. wheat. See also contango.

In the context of electricity generation, 'BoP' is all the infrastructure that supports the generator, but not the generator itself.

The lowest level of electrical demand, for a machine, site, country etc., over a given period (usually one day). See also peak load.

Groundwater which enters a river or other watercourse. As the level of groundwater is fairly stable, baseflow provides a steady minimum volume of flow.

An estimate of emissions of CO2e under current conditions, against which esimated emissions under alternative scenarios can be compared. Also known as the carbon, GHG or emissions baseline.

Negative sentiment with regards to the price or market for something, e.g. an expectation that the price of gas, or the level of a stock market, will fall.

Bioenergy with carbon capture and storage, i.e. the burning of biomass (which has absorbed carbon whilst growing) to produce energy, with a CCS system

The UK's largest energy suppliers, Centrica (previously British Gas), E.ON, Scottish and Southern Energy, RWE npower, EDF Energy and Scottish Power.

Mixed gases, typically methane, carbon dioxide and hydrogen sulphide, produced by the anaerobic digestion of organic matter.

Organic matter. As used in the energy industry, the term biomass generally implies that such organic matter will be burned to produce electricity and/or heat. Sometimes referred to as biofuel.

Hydrogen produced via gasification of bituminous coal, producing carbon dioxide, carbon monoxide and hydrogen.

Household wastewater from toilets.

Hydrogen produced via steam reforming with carbon capture and storage, ensuring that the CO2 by-product does not enter the atmosphere.

Hydrogen produced via gasification of lignite coal, producing carbon dioxide, carbon monoxide and hydrogen.

Business revenue derived from fossil fuel related activities, such as coal mining, oil and gas extraction and oil, gas and coal-based power generation.

Balancing Services Use of System charge. A flat fee for electricity generators, suppliers and transmission-connected users. Paid to National Grid ESO to cover transmission grid operating costs.

BMS. Integrated hardware and software to operate a building's lights, power, fire alarms, ventilation etc. Also known as a Building Automation System, or BAS.

Positive sentiment with regards to the price or market for something, e.g. an expectation that the price of electricity, or the share price of a company, will rise.

A charge by the DNO, to an electricity user, based on the Agreed Capacity for that user's site. Also known as Availability Charge.

Methods and schemes to reduce CO2e emissions, often as part of a carbon offsetting scheme aiming for net zero.

CCS. Industrial carbon sequestration. Various methods are being developed, but the main method currently in use is to capture waste carbon dioxide at the point of emission, then store it underground.

The processes through which carbon moves between living matter, soil and rocks, water and the atmosphere.

CO₂, by far the most common greenhouse gas emitted, and slow to degrade in the atmosphere. Emissions come predominantly through the burning of fossil fuels and through various industrial processes.

A measure of the greenhouse gas emissions (measured in CO2e) over the full life cycle of a product or service.

Schemes for displaying the emissions associated with a good, e.g. from the Carbon Trust.

CO, a greenhouse gas.

Balancing emissions with carbon avoidance or carbon removal schemes to reduce greenhouse gases in the atmosphere, moving towards net zero.

Methods and schemes to remove CO2e emissions from the atmosphere, often as part of a carbon offsetting scheme aiming for net zero. See also carbon sequestration and carbon capture and storage.

Any process, natural or otherwise, that removes carbon dioxide from the atmosphere and stores it in a carbon sink.

Anything which absorbs material amounts of carbon dioxide, including natural carbon sinks such as the oceans or plants or man-made sinks such as facilities formed from depleted oil reservoirs.

CCA. A UK scheme in which firms reduce their energy use and carbon dioxide emissions, in return for a reduction on their Climate Change Levy.

A UK business tax added to electricity, coal and gas bills by the supplier, who passes it on to HM Revenue & Customs. See also CCAs.

Construction, design and management advisor. Monitors a construction project and ensures compliance with the Construction (Design and Management) Regulations 2015.

A UK-based international climate standards non-profit, formerly the Carbon Disclosure Project.

CSS. An OFGEM service, launched in 2022, to accelerate the process of switching electricity and gas providers.

Chlorofluorocarbons. Various greenhouse gases, controlled by the Montreal Protocol, with CO2e values between c. 4,660 and 13,900.

Combined heat and power, an electricity generation method that makes use of the heat by-product, e.g. by co-locating a biomass-fuelled power station with an industrial activity that requires heat.

Business models that encourage extensive re-use of products and materials and significant reductions in waste.

Structural changes in weather conditions over time, usually referring to changes predominantly caused by human activity.

Carbon dioxide equivalent, a unit of measurement for the expected greenhouse effect over 100 years from a gas, e.g. one tonne of methane is equivalent to 28 tonnes of carbon dioxide.

Where the futures price for a commodity is higher than the spot price. This is normal for investment commodities, e.g. gold, because interest rates are the key pricing factor. See also backwardation.

The 26th UN Climate Change Conference of the Parties, a November 2021 climate summit for countries that signed the UNFCCC, held in Glasgow in the UK.

The 27th UN Climate Change Conference of the Parties, a November 2022 climate summit for countries that signed the UNFCCC, held in Sharm El Sheikh, Egypt.

The 28th UN Climate Change Conference of the Parties, a December 2023 climate summit for countries that signed the UNFCCC, held in Dubai, in the United Arab Emirates.

A phenomenon in high voltage power lines where the surrounding air is ionised, creating a faint glow and a hum and potentially damaging the wire.

A measure of electric charge, equal to the charge delivered by one ampere in one second.

The Carbon Reduction Commitment Scheme, previously applicable to large energy users, but closed down in 2019.

DA. A business which aggregates data from various electricity meters, and then re-cuts that data, e.g. by site or supplier. The MOP, Data Aggregator and Data Collector are often the same business.

DC. A business that collects the data from an electricity meter and ensures that it is sent to the electricity supplier. The MOP, Data Aggregator and Data Collector are often the same business.

DEC. A public sector version of an Energy Performance Certificate. Required for certain buildings operated by public bodies.

The removal or reduction in use of carbon dioxide from an industry, economy or the environment. In practice, other greenhouse gases are also often included when the term is used.

A default energy contract, which might occur when a user moves into a property or fails to renew a previous contract. Deemed contracts are usually expensive.

DSR. A change in electricity consumption in response to a signal or incentive. Often the change is a reduction in consumption, but it might also be an increase, or a delay. Requires real time coordination between power users and their suppliers and/or network operators.

The UK government's Department for Energy Security and Net Zero, responsible for energy supplies and prices, energy efficiency, green energy infrastructure and the UK's net zero commitment.

DER. Electricity generation and storage technologies that allow power to be supplied close to where it is used, often within a smart microgrid.

Electricity generation technologies that allow power to be supplied close to where it is used.

Short-distance, low voltage electricity infrastructure (typically wires on wooden poles), between the transmission grid and users. UK distribution is typically at 11,000 or 33,000 volts (though can be as low as 400 volts or as high as 132,000 volts).

An insulated pipe system to distribute heat from a central source to nearby commercial and residential buildings, common in northern and eastern Europe. Also known as heat networks or teleheating.

Distribution Network Operator. A licensed company that operates the distribution grid in one of 14 regions in Great Britain. Also known as a distribution system operator, or DSO.

A contract under which both electricity and gas are provided by one supplier.

The difficulties in managing grid stability with intermittent power from renewables. Named after the picture formed in a graph of electrical load throughout the day.

Distribution Use of System charges. Usage fees, Capacity Charges and standing charges paid to DNOs by those connected to the distribution grid, to cover installation, maintenance and operation costs.

Energy from Waste, or Waste to Energy. Generation of electricity (and sometimes heat) from waste materials (MSW). See RDF and SRF.

EV. Any vehicle that uses electricity as a means of propulsion (though usually referring to vehicles with no other fuel).

A form of energy resulting from the flow of an electric charge, usually along a metal wire.

Anything which consumes electricity, with 'electrical loading' referring to the amount of power required for that thing to operate.

The use of an electric current to cause chemical change in a liquid, e.g. oxygen and hydrogen are produced via the electrolysis of water (and the hydrogen produced is known as green hydrogen).

Gases (usually greenhouse gases) released from industrial (and sometimes natural) processes.

Defined in physics as the capacity to do work. Its many forms can be classified as either kinetic energy (e.g. motion, electrical, sound, heat) or potential energy (e.g. gravitational, nuclear, chemical, elastic). Measured in joules.

EaaS. A business model offering clients benefits in energy efficiency, security, or economics at minimal capital cost. Providers manage and fund the changes in return for ongoing fees.

EPC. An energy efficiency rating that must be available for certain buildings. The rating is from A (good) to G and is based on standardised information.

The uninterrupted supply of energy at stable and affordable prices. One art of the energy trilemma.

The difficulty in trying to balance the affordability, security and sustainability of energy.

An engineering, procurement and construction contract, in which the contractor delivers the whole project to the client on a 'turnkey' basis, with a set price, timescale and performance standards.

Energy service company. Broadly, an energy services provider, from generation to efficiency. More narrowly, a firm whose fees depend on reduced or cheaper energy for a client. See also Energy-as-a-Service.

Environmental, social, and governance. Three factors used to measure the sustainability, social impact, and non-traditional aspects of performance, for an investment or loan.

Energy Savings Opportunities Scheme, a mandatory energy efficiency assessment for most large UK and EU businesses (>250 staff, or sales > €50m (c. £43m) and total assets > €43m (c. £37m).

The European Union's system for the capping and trading of emissions, designed to create market incentives for decarbonisation.

The European Union's classification system for green and sustainable activities.

The European Union's policy response to the Paris Agreement, aiming for net zero by 2050.

Fuel cell electric vehicle. Use a hydrogen-powered fuel cell, rather than a battery, as the main source of electricity.

Any diet that is predominantly vegetarian but with small amounts of meat, fish and animal products.

A measure of the emission-equivalent miles travelled to bring food from its source to the consumer. Not intended as a complete measure and subject to certain criticisms.

Any device that converts the chemical energy of a fuel into electricity. Most commonly, hydrogen is combined with oxygen from purified air, with heat and water vapour produced as a by-product.

The heating of carbon-based material with minimal oxygen, generally above 500°C, in order to break down that material without combustion. See also pyrolysis.

One billion (1,000,000,000) tonnes, equal to 1,000,000,000,000 kg.

At 15° C and one atmosphere of pressure, one gigatonne of CO₂ occupies c. 534,800,000,000 m³. This would fill the whole of the UK up to 2.2 metres high (534,800,000,000 m³ / 242,495 km² = 2.21 m).

GWP. The climate warming impact of a greenhouse gas, estimated over a given period by the IPCC. Values for a gas can vary significantly with time, as some gases degrade quickly whilst others persist.

Nitrogen and hydrogen can be converted into ammonia through the Haber-Bosch process. When the hydrogen used is produced using in a sustainable way, the ammonia is considered green.

Building design based on minimising the environmental impact from the construction and use of buildings.

The UK government’s collection of approved methods for appraising the use of public spending.

Electrons carrying electricity derived from renewable sources.

Gas produced and consumed in a way that results in lower greenhouse gas emissions than its fossil fuel equivalent, e.g. methane produced through anaerobic digestion or pyrolysis, green hydrogen or biologically produced propane.

Hydrogen produced via the electrolysis of water, using electricity from renewable sources.

Molecules used to store and transport energy in a sustainable manner, typically hydrogen or another green gas.

Proposal from left wing of the US Democratic Party for a US transition to a more sustainable economy.

Business revenue derived from sustainability related activities such as alternative energy, energy efficiency, green building, pollution prevention or sustainable water.

Sunlight absorbed by the Earth's surface is radiated back as infrared light. Greenhouse gases then absorb that infrared, trapping the heat. A moderate effect creates a tolerable environment for life.

GHG. Any gas that allows sunlight through but which absorbs infrared (preventing the energy from the sunlight from returning to space), including carbon dioxide, methane, water vapour and others.

Any initiative or practice which is designed to seem environmentally beneficial but which lacks any material objective environmental benefit.

Hydrogen produced via steam reforming without carbon capture and storage.

Household wastewater from sources other than toilets, including from baths, showers, kitchen sinks and appliances.

The electricity grid, comprising the transmission grid and the distribution grid.

The secure, safe and balanced operation of an electrical grid. A grid cannot store electricity, so grid operators must manage changes in demand and supply (e.g. intermittent supply from renewables).

GSHP. Extracts heat from the ground using an electrically-powered pump to circulate a fluid (typically water and antifreeze) through underground pipes then into a heat exchanger.

Underground water, the volume of which typically changes only slowly, in response to changes in seasons or long term climatic or water use changes.

The global warming potential of a given gas as measured over 100 years. Note, this measure may understate the impact of methane, which has very high GWP but degrades quickly.

The global warming potential of a given gas as measured over 20 years.

HHD. The electricity consumption data collected from a Half Hourly Meter.

HHM. An electricity meter that sends data to the supplier every 30 minutes, via a fixed telecoms line. Compulsory for any business that consumes 100 kW or more, they are a type of AMR meter.

Resource-intensive industries where demand is growing or is difficult to reduce, including cement, steel and plastics manufacturing, and transport via road, air and sea.

Hydrochlorofluorocarbons. Various greenhouse gases, controlled by the Montreal Protocol, with CO2e values between 79 and 1,980.

The heat energy transferred across a surface, e.g. the wall of a building. Calculated as the u-value times the surface area, times the difference in heat either side of the surface.

Hydrofluorocarbons. Various greenhouse gases, controlled by the Montreal Protocol, with CO2e values between 4 and 12,400.

A highly reactive element. As such, on Earth it is usually found within a compound, such as water (H₂O). When separate and in normal conditions it is a found as an H₂ molecule.

Internal Combustion Engine.

Independent Connections Provider, a company that is accredited to build electricity network infrastructure to the required standards.

Investing with the intention to benefit the environment and/or society in addition to making a financial return. See also the triple bottom line.

IoT. Interconnected sensors, meters and other devices, typically on or in a piece of equipment, that exchange data wirelessly.

The Intergovernmental Panel on Climate Change, part of the UN's World Meteorological Organization and dedicated to providing scientific data regarding climate change.

A unit of energy, equal to i) a force of one newton moving an object one metre and ii) the energy lost as heat when a one ampere current passes through resistance of one ohm for one second.

One thousand Watts.

One thousand volt-amperes. Used to measure apparent power and the Agreed Capacity at a site.

Kilowatt hour, a unit of energy equal to one kilowatt sustained for one hour. kWhth and kWhe are used to specify thermal and electric, respectively. See also TWh and MWh.

A 1997 international treaty setting emission targets for 37 developed countries to reduce their emissions on average to 5.2% below 1990 levels.

Long duration energy storage, typically more than 8 hours. Below this, lithium ion batteries are often the best storage option. Above this, other technologies may be preferred, e.g. pumped hydro.

An increase in CO2e emissions in one country, area, industry or company that results from reduced emissions and/or stricter emissions rules in another country, area, industry or company.

LCoE. The total set up and running costs over the lifetime of an energy generator, divided by the total energy produced by that generator, where both are calculated on a time-discounted basis.

'A traditional heating system using 'low temperature hot water', i.e. with temperatures generally below 90° C.

One million Watts.

Minimum Energy Efficiency Standards, a set of standards for UK landlords that requires rented property to meet or exceed a given Energy Performance Certificate level, which rises over time.

CH₄, a common greenhouse gas produced by geological and biological processes, e.g. digestion by livestock. Methane's Global Warming Potential is high in the short term, but it breaks down rapidly.

An OFGEM category. A firm with fewer than 10 staff, and with sales or total assets not above €2 million, is a microbusiness. A firm that doesn't meet those criteria, but uses no more than 100,000 kWh of electricity or 293,000 kWh of gas per year, is a microbusiness for that fuel.

A local energy system, where demand is partly or wholly met by on-site generation and energy storage. See also smart microgrid and distributed energy resources.

Funding for climate-related contingency plans and risk reduction. See also adaptation finance.

A 1994 international treaty to reduce and control manmade substances that damage the ozone layer. Many greenhouse gases with very high CO2e values, e.g. chlorofluorocarbons, are controlled by the treaty.

Meter operator provider, a business that installs, operates and maintains electricity meters. A MOP must be contracted to look after any Half Hourly Meter. The MOP, Data Aggregator and Data Collector are often the same.

Meter Point Administration Number, a 13-digit number that is unique for each property supplied with electricity.

Meter Point Reference Number, a 6 to 11-digit number that is unique for each property supplied with gas.

Municipal Solid Waste, general waste from households and businesses. Consists of food waste and, if not separated pre-collection, garden waste, paper, cardboard, plastics, glass, metal etc.

Megawatt hour, a thousand kWh. MWhth and MWhe are used to specify thermal and electric, respectively.

The National Grid Electricity System Operator, which operates the transmission grid, installing and maintaining infrastructure, and ensuring grid stability.

A naturally occurring gas, predominantly methane and other hydrocarbon gases such as ethane, propane, butane, pentane, hexane, and trace amounts of carbon dioxide, nitrogen and other gases.

The position where emissions produced by a company, country or person are fully offset by schemes that reduce greenhouse gases in the atmosphere. Net zero is best viewed as a step towards zero emissions.

Businesses that operate electrical grids, gas distribution networks, and the related infrastructure. See also DNO and TNO.

The force required to accelerate one kilogram of mass at a rate of one metre per second squared.

NF₃, a greenhouse gas with a CO2e of around 16,600.

N₂O, a greenhouse gas with a CO2e of around 265.

Charges for using an electrical or gas grid and government charges levied on grid users. See DUoS and TNUoS.

Data from any electricity meter that is not a Half Hourly Meter.

Any electricity meter that is not a Half Hourly Meter.

An OFGEM category. Any firm that is not a microbusiness in respect of electricity, gas, or both. Note, it is possible to be a microbusiness for one fuel and a non-microbusiness for another.

The Office of Gas and Electricity Markets, the energy regulator for Great Britain. Note, the Utility Regulator governs electricity, gas, water and sewerage in Northern Ireland.

A unit of electrical resistance. Can be defined as the resistance present when one volt passes through a conductor and produces a current of one ampere.

O₃, a greenhouse gas.

A 2015 international treaty aiming to limit the rise in global average temperatures to below 2° C above pre-industrial levels, and to pursue efforts to limit it to 1.5° C.

Policies, decisions, business models etc. that are in line with the targets set out in the Paris Agreement.

The highest level of electrical demand, for a machine, site, country etc., over a given period (usually one day). See also base load.

Various greenhouse gases, controlled by the Montreal Protocol, with CO2e values between 6,630 and 11,100.

Any diet based on plants and fish, but excluding meat.

Hydrogen produced via the electrolysis of water, using electricity from nuclear sources.

Any diet based wholly or predominantly on foods derived from plants.

Any diet based on poultry and plants, excluding red meat and pork.

Active power over apparent power, typically 95% to 100% in a well-functioning electrical system. See also reactive power.

Power Purchase Agreement, a contract between an electricity supplier and a large-scale energy user.

Principles for Responsible Investment, an investor body that promotes six principles for sustainable investment. Initially proposed and supported by the UN, it is sometimes known as the UNPRI.

The heating of (mainly) carbon-based material in the absence of oxygen, at around 200°C to 800°C, in order to break down that material without combustion. See also gasification.

The reciprocal of the U-value. A high value indicates better insulation performance.

The change in energy in the atmosphere, in Watts / m². Positive radiative forcing (rising temperatures), may be due to the greenhouse effect, other atmospheric effects, or solar radiation changes. Also known as climate forcing.

Refuse Derived Fuel. Waste (MSW) which is processed into a fuel for an EfW plant. Typically this involves separation of recyclables and non-combustible material, shredding, drying and compression.

Electrical power that does not do useful work, but which is necessary for an electrical system to work well. It is typically 0% to 5% of the apparent power. See also active power.

Energy derived from a source that is naturally replenished, including solar, wind, water, geothermal and biomass.

The difficulty that an electrical current faces in moving through an object, measured in ohms.

Simplified Building Energy Model, a government-approved method of calculating the normal energy needed for heating, cooling, air conditioning and lighting for a commercial building.

Science Based Targets initiative, a non-governmental body that sets standards and provides methodologies to help firms reduce their carbon emissions and set net zero targets.

Direct pollution emissions from activities that a company controls, e.g. the combustion of fuel on site.

Indirect emissions from energy purchased and used by a company.

All other indirect emissions generated up and down a supply chain. Whilst difficult to calculate, focusing solely on scope 1 and scope 2 emissions can miss key impacts, e.g. by flattering 'bad' companies and failing to recognise the benefits from 'good' companies. See also leakage.

The Sustainable Development Goals, 17 social, developmental and environmental objectives published by the UN in 2015. They are the successor to the UN's eight Millennium Development Goals.

An electricity tariff where the price varies with the point in the year. See also Time of Day tariff and Seasonal Time of Day tariff.

SToD. Any electricity tariff where the price varies with the time of day and the point in the year. See also Time of Day tariff and Seasonal tariff.

The EU's Sustainable Finance Disclosure Regulation, a climate investments disclosure system designed to enhance transparency and reduce greenwashing. See Article 8 and Article 9.

A gas and/or electricity supplier that is not one of the Big Six.

A utility meter, produced under the SMETS standard, that automatically collects consumption data, and can both send data to, and receive data from, the electricity or gas supplier. See also AMR meter.

A microgrid with monitoring sensors and software controls to increase efficiency, respond to price signals, and balance energy demands, generation and storage. See also Internet of Things.

The UK's Smart Metering Equipment Technical Specifications, the standards governing smart meters. Currently the second generation rules are in force, known as SMETS2.

Solid Recovered Fuel. RDF that has been sorted and shredded to a higher standard to improve combustion efficiency in EfW plants.

Hydrogen production method based on turning methane and water into carbon dioxide and hydrogen through two chemical steps.

SO₂, a gas that causes atmospheric pollution, with some indirect climate effects. It is not considered to be a greenhouse gas.

SF₆, a highly stable (and thus long lasting) man-made greenhouse gas with the highest CO2e, around 23,500. Used to insulate electrical components, for which demand is growing as more renewables are connected to the grid.

Abnormal water on the surface of the land, due to very heavy rain, floods, rapid ice melt etc. Occurs when the ground below is saturated.

Normal water on the surface of the land, e.g. in lakes, rivers, wetlands, reservoirs and canals.

Synthesis gas, a manufactured mix of hydrogen and carbon monoxide, sometimes with carbon dioxide and/or methane.

Task Force on Climate-related Financial Disclosures. Formed by the G20 and the Financial Stability Board to improve climate disclosure (some standards are mandatory for large UK firms from 2025.)

ToD. An electricity tariff where the price varies with the time of day. See also Seasonal Time of Day tariff and Seasonal tariff.

Transmission Network Operators. Businesses that operate the electrical transmission grid or the gas transmission system.

Transmission Network Use of System charge. Fees for electricity generators, suppliers and transmission-connected users. Paid to National Grid ESO to cover transmission grid installation and maintenance costs.

One of several different measures of weight, not to be confused with a tonne. The short ton, still widely used in the US, is 2000 lbs, or around 907 kg.

A standardised international metric measure of weight, equal to 1000 kg.

At 15°C and one atmosphere of pressure (i.e. at sea level), one tonne of CO₂ occupies c. 535 m³. This would fill a tennis court to a height of just over 2 metres (534.8 m³ / (23.77 m x 10.97 m) = 2.05 m).

Time of Use tariff. Any energy billing arrangement that offers lower prices based on the time of consumption.

Manufactured fuel gas, usually referring to 'coal gas', which is produced by the gasification of coal. Also known as 'artificial gas' and now largely replaced by natural gas.

Third party intermediary, an energy broker.

Long-distance, high voltage electricity infrastructure (typically wires on steel pylons). UK transmission is at 400,000 or 275,000 volts.

When electricity is transmitted along a power line, some energy is lost to resistance and corona discharge. The amount varies depending on length of transmission, design and ambient temperature. In the US, around 5% of power is lost in transmission.

A process which combines CHP with cooling. Also known as CCHP, or combined cooling, heat and power.

The concept of making business and investment decisions based on the effects on people and the planet, as well as profit.

Hydrogen produced via the pyrolysis of methane, by passing natural gas through molten metal, plasma or thermal gas. If the energy source is renewable and the solid carbon by-product is permanently bound, the process is carbon neutral.

Terawatt hour, a billion kWh or a million MWh. TWhth and TWhe are used to specify thermal and electric, respectively.

The rate at which heat transfers through a material, measured in watt/square meter-kelvin (W/m²-K). Used to measure the insulating ability of a material or building, with a low rate indicating better insulation.

The UK's emissions trading system, operational since 1 January 2021 following the UK's departure from the EU. It is modelled on the EU ETS.

The United Nations Framework Convention on Climate Change, a 1994 international treaty to reduce the atmospheric concentrations of greenhouse gases.

The price per kWh for electricity or gas, or the price per cubic metre for water.

Large-scale production of electricity or other utilities, usually for sale to others rather than for local consumption.

Vehicle to Grid, interoperability and communication between an electric vehicle and the grid, allowing charging of the vehicle and for the vehicle to be a battery to aid with grid stability.

Vehicle to Everything, interoperability and communication between a vehicle and other entities, usually viewed as part of the Internet of Things.

Any diet based on solely on plants, excluding meat, fish and all animal products.

Any diet based on plants and animal products (e.g. milk and eggs), but excluding meat.

A measure of voltage. Can be defined as watts per ampere, or joules per coulomb.

A unit of electrical power which is sometimes equivalent to one Watt, but can also vary based on certain factors. See also kVA and Agreed Capacity.

The difference in electrical potential energy between two points, measured in volts. Analogous to a difference in pressure in a hydraulic system.

Virtual Power Plant, a distributed but coordinated network of small to medium electricity generators, electricity storage systems and/or power-consuming devices which use Demand Side Response.

The top surface of the layer of groundwater. Typically this is not horizontal, rather the profile is influenced by the land surface profile above, and with downward slopes towards nearby rivers.

A unit of power used to measure energy transfer, equal to one joule per second. See also kilowatt and megawatt.

A heating system which uses a liquid, usually water, to transfer heat.

Hydrogen that occurs naturally, found (rarely) in underground deposits.

In physics, the movement or change of an object. For movement in a straight line, it is measured as the force required multiplied by the distance moved. Measured in joules.

Used to refer to hydrogen produced via the electrolysis of water, either by using electricity from solar sources, or from mixed sources (some renewable, some fossil fuel based).

Where a company, country or person produces no greenhouse gas emissions, rather than just reaching net zero.

Our energy and climate glossary