Key terms and issues explained

Mae’r dudalen yma ar gael yn Gymraeg.

On this page you will find a range of key terms explained. Please click on a letter below to be taken to a list of terms and on "show" to read the explanation.

Economies of scale

Where the average costs of producing a good or providing a service falls as output increases.

Economy 7 / Economy 10

A type of tariff that has different unit rates for consumption during the day and during the night. The number following Economy refers to the number of hours for which night-time rates are available.

End of Fixed Term Notification

A communication from a supplier to a consumer, indicating that the fixed term period of the consumer’s energy supply contract is due to expire, and setting out the arrangements that the consumer will default to and the options available to the consumer to act in response to this notification.

Estimate of consumption

Estimate of the amount of energy used in a particular period of time, for example over the last three months.

Estimated annual cost/personal projection

The estimated cost of energy to a consumer over a 12 month period, based on a specified methodology and the best available information about that consumer’s consumption.

Evergreen contract

A tariff which is for a period of an indefinite length and which does not contain a fixed term period.