For peace of mind
Thankfully, the Government is committed to ensuring that all new build and extension projects comply with a sustainable approach. This goes for both domestic and commercial projects. Current UK building regulations require a certain number of lights within the building to be energy efficient: 

In the case of domestic applications the requirement is for one energy efficient light per 25 square metres, or one in four of the total light fittings, whichever is the greater. Roughly speaking this equates to 25% of lights that need to be energy efficient. Spaces such as garages and store rooms cannot be included within this calculation.

For commercial buildings the regulations are slightly more complex. Rather than being based on number of fittings, an average overall light output of 45 lumens per circuit watt or more is required for the lighting scheme. In some cases (bars and hotels) this increases to 50 lumens. Essentially this means that most lights will need to be energy efficient.

The future will no doubt see further tightening on the energy efficiency requirements with proposals already in the pipeline particularly on domestic properties.