Our principal operations are critical to the functioning of the economies we serve. The reliability of our energy networks is one of our highest priorities after safety.

In the UK, the total amount of electricity transmitted in 2009/10 was 287 TWh compared with 286 TWh for 2009/10. In the UK, the winter of 2010/11 saw demand from the electricity transmission network in England and Wales hit a peak of around 53 GW.

In the UK, Gas transmitted amounted to 1,199 TWh, compared with 1,150 TWh in 2009/10. 20. The maximum gas demand on the UK National Transmission System was 465 million standard cubic metres on 20 December 2010. Gas demand in the US was 218 TWh.

In the US, annual electricity transmission network peak demands were 7.58 GW in New England and 6.91 GW in upstate New York.

We use business specific performance indicators to measure our reliability performance. More information on the reliability of each of our businesses is included in the business sections on page 45 of our Annual Report and Accounts 2010/11.