 The concept of the Energy Park was extended into non-residential buildings built across Watling Street in Knowlhill where a number of low energy office buildings have been constructed including the two phases of the headquarters buildings of the National Energy Foundation.Another area where Energy World continues to have an impact derives from the Milton Keynes Energy Cost Index (MKECI) , which was used to calculate the energy efficiency of the Energy World houses.Based on the results and feedback from Energy World, this was to evolve into the UK's first national energy efficiency rating scheme for buildings, with the launch in 1990 of the National Home Energy Rating scheme (NHER) .