While the ship is at sea, there must be available at all times a supply of electrical energy sufficient to operate the radio installations and to charge any batteries used as part of a reserve source of energy.

Both the VHF and MF/HF installations must be simultaneously supplied.

A means of ensuring a continuous supply of electrical power must be provided to all GMDSS equipment that could be affected by an interruption in power.

If a UPS or equivalent is used to supply power to the ship's GPS receiver or other source of positional information, a means must be provided to ensure the continuous supply of the information in the event of a failure to the ship's main or emergency source of power.