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Active Power

Active power is the rate of producing, transferring or using electrical energy. This is measured in watts and often expressed in kW or MW and can be referred to as ‘Real Power’ or ‘Power’.

Agreed Capacity

An agreed amount of electrical load or supply, with the local Distribution Network Operator (DNO), at a property or address.

Air Source Heat Pump (ASHP)

A renewable heating system that uses electricity to take warmth from the air outside and repurpose it to heat and warm water. The machine absorbs the heat into a fluid, compresses this fluid to increase its temperature, then sends the resulting hot water to radiators or a underfloor heating system.


Automated Meter Reading - A meter which automatically collects usage data. This then transfers to a central database for billing.
AMR is the term given to a system that provides automatic meter readings remotely. It uses telephone technology and holds the ability to transfer data into a billing system.


Annual Quantity - This is the amount of gas that a site or meterpoint is expected to use, on average, in one year.

Availability (kVA)

Availability (kVA) or Agreed Capacity refers to the energy capacity limit for a site.
For example, if a site has an Availability of 150 kVA then the energy usage should not exceed that figure at any time.

Back Billing

This is a bill that is sent by your gas or electricity supplier to catch you up if you have previously been incorrectly charged for your energy use. There is a limit to how far back this can go and when your supplier is allowed to back-bill you for.


When market prices are cheaper for a future purchase than the current market prices and the opposite market condition to contango. Some storage facilities tend to switch off during backwardated market periods.

Base Load

This is the level of which electricity demand would never fall under. For example, a site with a maximum demand of 750 kVa, their level would never drop below 250 kVa, aka their base load.


A common term when talking about energy prices. When it's believed the market costs are about to decline or have declined.


Department for Business, Energy & Industrial Strategy. The department has responsibility for: business, industrial strategy, science, research and innovation, energy and clean growth and climate change.

Bill Language

On energy bills you may see the following letters:

A - This is for the ACTUAL reading.

E - This is for the ESTIMATED reading.

C - Means the CUSTOMER provided the reading.

Biomass & Biofuel

Biomass or biofuel is the use of plant-based material or organic matter to make fuel to produce heat or electricity. Sometimes this can be from industry or home waste such as wood pellets and is classed as a 'carbon neutral'. The carbon dioxide released during the generation of energy is balanced and absorbed by plants.


A common term when talking about energy prices. When it's believed the market costs are about to rise or have risen.

Capacity Charge

Also known as the Availability Charge. This is a set charge by the local Distribution Network Operator (DNO) for the maintenance of the electricity network, based on the Agreed Capacity of a property.

Central Switching Service (CSS)

The Centralised Switching Service has been created to make switching energy suppliers faster, more reliable, and more efficient. Consumers will be able to transfer data, payment details and account information the next day.
Previously it took three weeks to switch your gas or electricity supplier and many people found that the process was too complicated, too slow, and too often went wrong.

Competitive tender process

Competitive tendering generally promotes competition, transparency, and gives suppliers an equal opportunity to win business by bidding for it.


The opposite to a market condition ‘backwardation’ when market prices in the future are higher than current prices. This situation generally encourages a build-up of inventories. Contango is the opposite market condition to backwardation.

Cooling-off period

This is the period of time after the consumer has entered into a contract or signed up to a tariff where they can still break out of the contract without incurring cancellation fees.

Deemed Energy Contract

This is when one of your current contracts ends but your supplier continues to supply you, as no renewal has been set up. It can also occur if you move into a new business premises and don’t immediately agree a contract.
Deemed contracts are more expensive and is the supplier’s most basic offering. E.g. Deregulation of water in 2017.

Distribution Network Operator (DNO)

The DNO is the company that owns and operates the power lines and infrastructure that connects you to the Grid supply.

Dual Fuel (DF)

This is an energy contract where a customer takes electricity and gas from the same supplier (or two affiliated suppliers).


Distribution Use of System (DUoS) charges:
This covers the cost of maintaining + installing local networks and is paid to your Distributor Network Operator.

Transmission Network Use of System (TNUoS) charges:
This covers the cost of installing + maintaining the transmission system across England, Scotland, Wales and offshore, and is paid to the National Grid.

Erroneous transfer

When an energy supplier tries to take over a gas or electricity supply by mistake. Compensation can be claimed in some incidents if the customer is 'out of pocket' with higher rates and for the inconvenience.

Evergreen contract

A tariff which is for a period of an indefinite length, without a fixed term period or end date.

Greenhouse effect

When energy from the sun goes through the planet’s atmosphere, rather than being released back into space, it becomes trapped and causes temperatures to rise.

Green tariff

A supplier's promise to match all or some of the electricity you use with renewable energy, which then feeds back into the National Grid. So, the more people who sign up to a green energy tariff, the bigger the percentage of green energy in the national supply!

Half Hourly (HH) Data

These meters are electronically read by the supplier every 30 minutes for a more accurate billing.


This is calculated as a proportion of other costs and allows suppliers to offer competitive deals underneath the set level of a price cap. It allows customers to choose the best deal for them.

Large energy suppliers (The Big Six)

The large energy suppliers (often referred to as the 'Big Six') are the companies that hold supply licences and supply most of the energy to domestic households in the GB market.

Centrica Plc (also know as British Gas)
Scottish and Southern Energy (SSE)
RWE npower
EDF Energy
Scottish Power

Market segmentation

Splitting customers, or potential customers, in a market into different groups, or segments.


An organisation is classed as a microbusiness if they meet one of the following criteria…
• Employs fewer than 10 full-time employees and has an annual turnover no greater than €2 million (or balance sheet value)
• Uses up to 100,000 kWh of electricity per year
• Uses up to 293,000 kWh of gas per year


The Meter Operator (MOP) provides and maintains your electricity meter and communications. MOP = Meter Operator Provider.

A Data Collector (DC) is responsible for the collection and processing of your electricity data and delivering that data to your supplier.

Data Aggregator (DA) - Data Aggregators aggregate data to be submitted into Settlements so that accurate values of what a Supplier’s customers have “taken” is allocated to enable the accurate billing of that Supplier for the energy their customers have used.


Meter Point Administration Number (MPAN), also known as the Supply (S) Number, is unique to a property and is used by suppliers to decide your electricity rates.


Meter Point Reference Number (MPRN) is a unique 11 digit number used to identify a property and is used by suppliers to decide your gas rates.

National Grid ESO

The National Grid Electricity System Operator (ESO) is the electricity supplier for the UK. They make sure that electricity supply meets demand all day, every day.

Network Operators

Network Operators are responsible for running pipes and wires that bring gas and electricity to our homes and businesses. There are different owners in different parts of the country.

Non-Half Hourly (NHH) Data

Non-half hourly meters are for smaller power users that are supplied on monthly or quarterly tariffs.


The Office of Gas and Electricity Markets - an independent energy regulator for Great Britain who promote competition in the energy markets and regulate the gas and power networks.

Ombudsman services

Have been appointed by Ofgem (the UK gas and electricity regulator) to independently handle disputes between consumers and energy suppliers.

Shipperless Meter Point

A supply point that doesn’t currently have a registered shipper although it has in the past. Gas is being consumed through the meter but is not being charged as it doesn’t belong to a supplier at present.

Small Suppliers

Suppliers which operate in the domestic gas and electricity market but do not hold significant market share. This can refer to all suppliers other than the Big 6.

Standard Variable Tariff

A Standard Variable Tariff (SVT) - is an energy supplier’s basic offering and generally happens if a customer does not choose a specific energy plan.
For example, after their fixed contract or tariff ends, they are moved to an SVT until they choose a new one. It has an indefinite length and does not have a fixed term.

Standing Charge

A fixed monthly or daily amount that is paid to your electricity and gas supplier for maintenance and other costs, such as maintaining connection to the power network.

Surface Water

Rainwater that runs off roofs, gutters, pond overflows, public highways and driveways, that is classed as quite clean. This gets drained away and safely returned to watercourses. It appears as a charge on water bills and normally part of the standing charge fee.

Switching window

When a consumer reaches the end of their contract, there is a window of time when they can switch energy supplier. This is in accordance with their notice period, which can be found in their T&Cs.

Take-or-Pay (ToP)

With some suppliers, this is as an agreed minimum amount of gas/electricity to be used in a period of time, as part of the contract. Failure to use this amount still requires the buyer to pay for the full contracted volume.

ToU Tariff

Time of Use (ToU) tariff is when the charge varies depending on the time that the energy has been consumed. For example, the difference between day and night charges.

Transmission Network Operators

There are two different types of Transmission Network Operators in the UK...
National Grid operate most of the country's gas pipe networks, transporting energy from gas fields to end users. There are also Independent Gas Transporters (IGTs) who privately run as an additional option.

Unit Rate

The unit rate is the price-per-unit of both gas and electricity. For example, electricity is measured in kWh (kilowatt per hour) so a unit rate is the cost of each kWh used!

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Part of the Zenergi family

We are preferred partner and supplier to many associations including ASCL, WASBM, LASBM, BASBM, CAPSA and have been in partnership with some for over a decade. We regularly attend their conferences and give members the Positive Zenergi experience based on their needs.

Zenergi are also an approved partner with the Institute of School Business Leadership, offering ISBL members the provision of a customer service specialising in energy procurement, invoice validation and contract management.

We are proud in our unique offering, based around customer service excellence. We audit the suppliers we work with to make sure our customers are getting the best value and service and are pleased to offer OJEU compliant pricing.