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From dual fuel to erroneous transfers, the world of gas and electricity can be a confusing place – in part due to the sheer volume of jargon out there. Luckily for you, we’ve put together this A-Z of energy market terminology to help you make sense of those bills.

Actual read

You'll usually see this on correspondence from your energy supplier. An actual read is a manual meter read taken by the customer, as opposed to the estimated read which is decided based on previous usage. 

Annual quantity

The amount of gas consumed per year.

Big Six

You'll often hear us refer to Big Six energy companies when we're talking about different providers. The Big Six are the largest suppliers in the UK and are as follows: British Gas, E.ON, EDF Energy, Npower, Scottish Power and SSE. 


This stands for British Thermal Units and refers to the amount of heat used by an appliance. BTU is used to work out your estimated annual quantity for new heating equipment. 

Capped plans

On a capped plan, the amount you pay for each unit of energy will remain the same for a set period of time, while it can't increase it may reduce if gas and electricity prices fall. 

Calorific value

The amount of heat released when your gas is burned is known as CV (calorific value). 


Designed to improve energy efficiency, the Climate Change Levy is a tax for businesses on energy usage. 


The Distribution Network Operator is the company that maintains the electricity network. 

Dual fuel

Dual fuel is where your gas and electric bills are consolidated into one plan.


Also known as Estimated Annual Consumption, EAC is your estimated energy consumption for the upcoming year based on your past meter readings. 

Economy 7

This is a type of energy tariff that lets you pay lower rates per kWh during the night. 

Economy 10

This is a type of energy plan whereby you pay normal prices most of the time, but you receive cheaper rates during ‘off-peak’ periods. Those ‘off-peak’ times are usually specified by the energy provider are and spread throughout the day.

Energy monitor

An energy monitor is a device that shows you how much energy you're using in real time. Learn all about them in our handy energy monitor guide.

Estimated bills

Often energy suppliers will estimate your usage based on the average for your area and building type. If you'd rather get a more accurate read, you can request to submit manual readings. If you'd like to make that process even more streamlined, you could look into installing a smart meter which automatically sends your exact usage to your supplier. 

Erroneous transfers

Sometimes energy suppliers accidentally switch the wrong person's supply when transferring to a new provider, this is what's known as an ET or erroneous transfer. 

First and next units

These are the different pricing bands for energy bills. Customers are usually on first unit price and will eventually be moved on to next unit price at a later date depending on the tariff. 

Fixed rate

If you’re on a fixed rate plan, your provider will freeze your energy rates for a set period of time. This means you won’t need to worry about price increases during your contract. Learn more about the different types of energy plans here.

Gas safe register

As the official gas registration body in the UK, all gas engineers must be on the Gas Safe Register.

Green Energy

This is a type of energy that is generated from natural, renewable sources such as solar power and wind. Read all about it in our Green Energy guide


A GW is a gigawatt used to measure power.


A kilowatt is a measure of power and is comprised of 1000 watts. 


This stands for kilowatts per hour, this is how your energy consumption is calculated. 


A Levy Exemption Certificate means that the holder doesn't need to pay a Climate Change Levy charge on top of their business electricity charge. 


A Meter Operator is the company responsible for energy meter installation and maintenance. 


The Meter Point Administration Number is your unique 21 digit electricity supply number, you can find yours on your electricity bill or by calling your electricity distributor. 

MPAN state

Your MPAN state refers to the way your electricity supply is identified. It will either be live - where the supply is fully operational, de-energised - where the meter is connected to the distributor but no electricity can be used, or it can just be disconnected meaning that the MPAN won't be used in the future. 


Your MPR stands for Meter Point Reference and is used to identify your gas supply. This can be found on your gas bill, if you haven't got one to hand you can call the National Grid to find out. 


Not to be confused with the popular 90s instant messaging app, the MSN is actually your Meter Serial Number. This identifies your physical meter as opposed to the supply.

No Standing Charge / Nil Service Charge

Some energy plans come without a standing charge (this is the fixed price set by a supplier that you have to pay each day for being given access to your gas and electricity) If your Standing Charge is covered with your tariff payments you may see No Standing Charge or Nil Service Charge written on your statement. 


The Office of Gas and Electricity Markets is the energy market's government regulator for the UK. They set policies and make decisions across the industry. 


Pence Per Unit is the most common method for charging customers.

Prepayment meters

With this special type of meter, you pay for your energy up front using a key or card rather than on a credit plan. Find out more about prepayment meters and whether they're right for you with our handy guide

Renewable energy

This is an energy supply that comes from sources that renew themselves naturally, such as water, sun and wind.

Single fuel plans

If you buy your gas and electricity from different suppliers, you’ll be on a single fuel plan. This can sometimes work out more expensive than dual fuel, you can use our Energy Saver app (available on Google Play and the App Store) to find out if you could be saving money on your energy bills by moving to a dual fuel deal.

SMETs1 and SMETs2

SMETs stands for Smart Metering Equipment Technical Specifications. These are the 2 different types of smart meters that have been rolled out to energy customers. SMETs2 is the most recent version, it communicates with your provider using a secure Government data network which is easily compatible with other suppliers should you choose to switch. SMETs1 meters on the other hand connect to your energy supplier through 3G, similar to a mobile phone. The trouble is that the data from these meters can't be read by all suppliers which makes switching suppliers tricky. You can find out more about smart meters here


This stands for your Supply Start Date, if you're switching suppliers you'll want to ensure this lines up with your old provider's expiry date. 

Standard plans

If you’ve not chosen a specific deal with your energy supplier, you’re more than likely on a standard plan. These are usually the most expensive so it pays to see if your provider offers any other deals. Use our Energy Saver app (available on Google Play and the App Store) to find out if you could be saving money on your energy bills.

Standing charge

Most energy tariffs have a standing charge, this is a combination of gas and electricity supply fees as well as fixed network service charges.

Transportation charge

This is what the National Grid charge for the national transportation of gas through the gas network.


Variable Direct Debit is how much you’ll pay monthly to cover the cost of your billed consumption. This usually means you’ll pay a reduced standing charge.