The Institute of Electrical Engineers recommend testing of commercial buildings every 5 years or change of occupancy (if sooner), but the Electricity At Work Regulations and the Electricity Supply Regulations are of particular importance here.

The Electricity At Work Regulations 1989 requires that "..as may be necessary to prevent danger, all systems shall be maintained so as to prevent, so far as reasonably practicable, such danger.."

The frequency of Test and Inspection must take into account:

(1) The type of installation
(2) Its use and operation
(3)The frequency and quality of maintenance
(4)The external influences to which it is subjected

Most insurance companies are now insisting that regular inspections are carried out on their clients premises, and failure to do so can in some cases mean that insurance can be null and void.