If your air-conditioning system has an output of over 12kW, you need to meet certain requirements for inspecting the energy efficiency of your systems. If you have more than one air-conditioning unit within a building they are considered to be a single system.
In England, Northern Ireland and Wales, from 4 January 2011, if your air-conditioning system has an output over 12kW it must be inspected at least every five years. If your system was first put into service on or after 1 January 2008, it must have its first inspection within five years of the date when it was first put into service.
Inspections must be carried out at least every five years by an accredited energy assessor who will assess the efficiency of the system and advise on improvements.
Source: NetRegs