Like many industries, the energy industry has developed an language all of it's own. Brokers and suppliers talk about Duos Charges and Triads and avialabiity, but what to they actually mean?

We've put together what we think is the most complete glossary of energy terms on the net, if you can't find what you're looking for here give us a call and we'll see if we can help you.


Daily Balancing:

Balancing, on a day-by-day basis, the amount of gas a supplier puts into and takes off a pipeline system.

Data Aggregator (DA):

The Data Aggregator or DA is the organisation appointed for aggregating the meter- reading data received from the Data Collectors and forwarded to the suppliers

Data Collector (DC):

The Data Collector or DC is the organisation responsible for collecting, processing and validating the meter reading data, who then passes the information to the Data Aggregator

Day-Ahead market:

The market trading for the day before the operating day.


Department of Environment, Food and Rural Affairs of the UK Government.


A measure of the variation of one day’s temperature against a standard reference temperature, typically 65 degrees Fahrenheit (18 degrees Celsius). Degree-days are used as a base for temperature-related weather derivative deals. There are both cooling degree-days (CDDs) and heating degree-days (HDDs).  For example a firm take out a 30-day CDD swap with a reference temperature 65 degrees F, and the average temperature on each day is 70 degrees F. The company is then due 150 (30 x 5) degree-days multiplied by the sum of money agreed for each degree-days. If the firm had taken out an HDD swap, it would have owed the same amount of money.


Option risk parameter that measures the sensitivity of an option price to changes in the price of its underlying instrument.

Delta Hedging:

An option is delta-hedged when a position has been taken in the underlying that matches its delta. Such a hedge is only effective instantaneously, because the option’s delta is itself altered by changes in the price of the underlying, interest rates, the option’s volatility and time to expiry. A delta-hedge must be rebalanced continuously to be effective.

Demand-side management:

Activities carried out to control the level and type of demand for electricity.


A financial instrument derived from a cash market commodity, futures contract or other financial instrument. Derivatives can be traded on regulated exchange markets or over- the-counter. For example, energy futures contracts are derivatives of physical commodities, and options on futures are derivative of futures contracts.


Distributed Generation Co-ordination Group, which is advising Ofgem on the effects of distributed generation on the UK electricity network.

Diesel generator:

Emergency generator used to restore essential supplies after loss of generation to enable safe shut down.


Where natural gas is put into a pipeline system at one end and the same amount of gas is delivered at another point, although the gas may not have been transported between the two points

Distributed Generation:

A distributed generation system is characterised by a number of smaller, interlinked generators, rather than one central generator. Distributed generation is typically connected at low voltage, i.e. to the distribution network. Otherwise referred to as Embedded Generation, this is generation that is typified by avoiding supplier transmission and distribution costs. Most often treated as negative demand by suppliers.

Distribution network:

Network for electricity distribution at voltages below that of the transmission network.  Typically 11kV or 33kV.


Declared Net Capacity. The equivalent capacity of intermittent plant adjusted from the rated capacity using a correction factor to enable comparisons with continuously operating plant.


Distribution network operators.

Dry Gas:

Gas with a low liquid content, usually below two gallons per 1,000 cubic feet. This may happen naturally, as in most of the fields in the southern North Sea, or the water content may be reduced by a dehydration process. Also known as lean gas.


Department of Trade and Industry.


Digest of UK Energy Statistics, an annual publication from DTI.

Dynamic plant data:

The operating parameters and running conditions for a plant. This data is used by the System Operator in accepting/declining bids or offers. Example: Maximum Delivery: Volume.