Main switch circuit breakers in WA: what the rules say

By Elysium Electrical Contractors | Licence EC 16523 | Sources: WA Electrical Requirements, August 2023, and Western Power requirements, April 2023 | Last checked 24 October 2026

Every electrical installation in Western Australia needs a main switch. Western Power says a main switch circuit breaker must be installed when a new premises is connected or an existing connection is altered. This is our plain-language summary of what the official documents say. [1][2][3]

Two devices, not one

The WA Electrical Requirements say both a service protection device and a main switch are required in all consumer installations. [1]

The service protection device is there to electrically protect the consumer’s mains and metering equipment from the effects of short circuit faults within the installation. It also provides a point of electrical isolation for safe replacement of metering equipment, for electrical contractors, and for the network operator. [1]

Western Power’s requirements say the service protection device does not replace the installation main switch and must not be treated as overload circuit protection for the consumer’s installation, equipment, consumer mains cable or circuitry. [2]

What Western Power requires

Western Power says that if you are connecting a new premises to its network, or altering an existing network connection, you are required to install a main switch circuit breaker. It gives solar systems, EV chargers, large appliances and air conditioners as examples. [3]

Its Western Australian Service and Installation Requirements say that, where required by the network operator, the consumer’s main switch must be a circuit breaker with visible and lockable isolation facilities. The document calls this a mandatory requirement for all connections to the Horizon Power and Western Power distribution networks. [2]

A single main switch must be rated to the lesser of the network connection service or the allocated capacity agreed for the installation. [2]

When an existing connection is altered

The same document says that when a consumer starts an alteration, addition or relocation of an existing network connection or metering equipment, the altered arrangement is classified as a new installation. It must be upgraded to comply with the Western Power requirements, section 6 of the WA Electrical Requirements, the Metering Code and other applicable requirements and standards. [2]

It also says that connecting embedded generation, energy storage systems or vehicle charging to an existing network connection is classified as an alteration. [2]

The document says its requirements are not retrospective, unless an existing consumer electrical installation or part of it is altered, modified or upgraded, or constitutes a safety issue as determined by an authorised inspector. [2]

Three-phase homes

Western Power says homes with a three-phase connection require a linked three-phase circuit breaker. If all the load sits on one phase, the main switch may trip, and the electrician must spread the load evenly across the phases. [3]

If the breaker trips more often

Western Power says the circuit breaker is designed to trip when service capacity is exceeded. If tripping increases after installation, an electrician should review your total load. If it exceeds your allocated capacity, you can authorise the electrician to apply for a supply upgrade, or apply yourself. [3]

An electrical contractor installs the circuit breaker on the switchboard or meter box. The contractor must assess your electrical demand against Australian Standards and Western Power requirements. If the demand is likely to exceed a standard connection service, an application to upgrade the connection may be required. [3]

Our suggestion, not an official requirement: if you are adding solar, a battery, an EV charger or an air conditioner, ask your electrician whether the job counts as an alteration to your connection.