In a change from previous practice the 2004 workbook contains only data for calendar year 2004. Data for earlier years are available from the website as CSV files

To create demand by postcode for earlier years it is necessary to load both the data and the summary sheet, which are both in the same format as in this workbook, and carry out the calculation as described below.

1. Worksheet Data2004 contains gas demand (Annual Quantities in kWh) and customer numbers by postcode using the DTI's "Rule of Three" to ensure confidentiality (i.e. no item of AQ data refers to less than 3 supply points). A Transco Local Distribution Zone (LDZ) identifier has been added to enable cross reference with actual flow data for the relevant year in question.

Note: the AQ of a customer is its estimated annual consumption over a 365 day year under average weather conditions based on 71 years of weather. Consequently it will be different to the actual gas consumption. In addition not all loads are included within this dataset.

2. Worksheet Sum2004 compares the sum of the postcode demand to the actual gas demand by LDZ "assuming two separate weather conditions; one based on the average of 71 years, and other based on 35 years which allows for the impact of "Global Warming".

3. To create actual demand by postcode simply take the postcode you are interested in and use the appropriate % correction to scale the Domestic (0-73 MWh) and Industrial & Commercial (>73 MWh) to the correct level For example, in Scotland increase the domestic postcode data by 3.3% and for non-domestic decrease by 6.7% when scaling to the 35 year weather basis.

Some large Industrial and Commercial sites are not included in the main Transco Billing system so do not feature in the AQ by postcode data set for the Industrial and commercial sector

These loads, referred to as Unique Sites, are included as a separate line in the summary sheet, which are combined with the smaller I&C AQs to give a total non-domestic AQ for use in the scaling.

There are some customers, for example domestic customers in new housing estates, who are not connected directly to the Transco system. These small networks, knows as CSEPs or Connected System Exit Points are not included in the AQ data. They are included in the annual demand data which accounts for about half the difference between the AQs and the annual demand on the 71 year basis.

We recommend all the postcode analysis is scaled to the 35 year weather basis as the 71 year weather basis underestimates recent climate warming.

4. LDZ identifiers are consistent with those applied under the Network Code and are as follows:
SC = Scotland
NO = Northern
NW = North Western
NE = North Eastern
EM = East Midlands
WM = West Midlands
WN = Wales North
WS = Wales South
EA = Eastern
NT = North Thames
SO = Southern
SE = South Eastern
SW = South Western

For a map of these LDZs please refer to our 10 Year Statement