The defintion of an electrical installation requiring a COC is:
“electrical installation” means any machinery, in or on any premises, used for the transmission of electricity from a point of control to a point of consumption anywhere on the premises, including any article forming part of such an installation irrespective of whether or not it is part of the electrical circuit, but excluding -
(a) any machinery of the supplier related to the supply of electricity on the premises;
(b) any machinery which transmits electrical energy in communication, television or radio circuits;
(c) an electrical installation on a vehicle, vessel, train or aircraft.
So it seems the power generating portion (the supply) wouldn't need a COC, but the installation it supplies would.