Consumer mains are the cable running from your point of attachment to the main switchboard. Submains run onward from that main switchboard to a separate switchboard elsewhere on the property, such as a unit, a granny flat, a shed or a tenancy. Consumer mains are Level 2 ASP work. Submains are usually standard licensed electrical work.
The two terms get swapped around constantly, and which one a quote or a defect notice uses decides who may do the work, who signs it off, and who pays. Here is where one stops and the other starts.
What are consumer mains?
Consumer mains are the single set of conductors carrying power from the point of supply on your property to your main switchboard. The point of supply is the point of attachment where an overhead service line lands on your wall or pole, or the pit where an underground service comes in. Everything on the network side of that point belongs to Ausgrid. Everything from that point inward, consumer mains included, belongs to you.
There is normally one set per property, sized for the load of the whole installation. If yours are undersized or no longer legal to reconnect, see do you need a consumer mains upgrade.
What are submains?
A submain is any set of conductors running between one switchboard and another switchboard inside the same installation. It leaves a protective device in the main switchboard and finishes at a distribution board somewhere else on the property. Nothing about a submain touches the network.
Submains appear wherever power travels a distance and then splits again:
- A block of units, where a submain runs up the riser to each unit's own board.
- A granny flat or secondary dwelling with its own board.
- A detached garage, shed, studio or pool board at the back of the block.
- A commercial building, where each tenancy or floor has its own board.
The quick test: if the cable ends at a board with its own main switch and breakers, it is a submain. If it ends at a power point or a light, it is a final subcircuit.
Where do consumer mains stop and submains start?
The main switchboard is the dividing line: consumer mains arrive at it, submains leave it. A standard single house with one switchboard usually has no submains at all.
| Feature | Consumer mains | Submains |
|---|---|---|
| Runs from | Point of attachment or underground pit | The main switchboard |
| Runs to | The main switchboard | Another switchboard or distribution board |
| How many per property | One set | None, one, or many |
| Protected by | The service fuse at the point of supply | A circuit breaker in the board it leaves |
| Who can work on it | Level 2 ASP only | Any licensed electrician |
| Network disconnection needed | Yes | No |
Who owns the submain, and who pays to fix it?
On a single-title property the owner owns everything from the point of attachment inward, submains included. Strata is where it gets argued. There the answer turns on what the cable feeds rather than where it runs: a submain feeding more than one lot is common property and the owners corporation repairs it, while a cable serving only your lot is yours even where it passes through a common wall. The full breakdown is in who pays for electrical repairs in a strata building. Between a landlord and a tenant it is simpler: a submain is part of the building.
Not sure which cable you are looking at?
DM Electrical is accredited for Level 1 and Level 2 ASP work and based in Brookvale, so the mains, the switchboard and the submains get sorted in one visit rather than across two trades. Available 24/7 across the Northern Beaches and wider Sydney.
Does a submain need a Level 2 electrician?
Usually not. A submain sits inside your installation, so any licensed electrician can install, repair or replace one. Consumer mains form part of the service connection, so replacing them means disconnecting and reconnecting the property, and only an accredited Level 2 ASP is authorised to do that.
Submain work often lands alongside work that is Level 2, because adding a granny flat board can push the property past what the existing mains and switchboard were sized for. In that case one accredited team can do the lot rather than two trades waiting on each other. Either way the electrician must lodge a Certificate of Compliance Electrical Work.
What size should a submain be?
A submain has to carry the full demand of everything downstream of it and still deliver usable voltage at the far end, which is why length matters as much as load. The wiring rules cap total voltage drop at 5 percent from the point of supply to the furthest point of use, and a long run to a back shed uses much of that budget before anything is switched on.
Two things drive the sizing. Maximum demand is the calculated load of every circuit the far board feeds, not the sum of the breaker ratings, so a board running a cooktop and a hot water unit is a different number from one running a few power points. Run length matters separately: a 40 metre run to a studio can need a larger cable than a 5 metre run carrying the same load.
What goes wrong with submains?
The most common submain problem is not a fault at all, it is a cable too small for what has been added behind it. The original run was sized for a shed with a light and a power point, then a workshop and a pool pump went on the end of it. The symptoms are easy to mistake for something else:
- Lights dimming in the flat or shed when a large appliance starts, while the rest of the property is unaffected.
- The breaker feeding the submain tripping under load when nothing at the far board is faulty.
- Total loss of power to one building while the main switchboard shows nothing wrong.
Buried runs fail differently, and the damage rarely announces itself until an RCD starts tripping in wet weather. A switchboard upgrade is usually when it surfaces, because a new board makes the state of the cable feeding it obvious.
Frequently asked questions
Is a submain the same as consumer mains?
No. Consumer mains run from the point of attachment to the main switchboard, and there is only one set per property. Submains run from that main switchboard onward to another board, such as a unit board, a granny flat or a shed. Consumer mains are Level 2 ASP work because they form part of the service connection. Submains sit inside your installation and can be done by any licensed electrician.
Do I need a Level 2 electrician to replace a submain?
Not usually. A submain is internal wiring, so a licensed electrician can replace it without disconnecting the property from the network. You need a Level 2 ASP when the job also touches the consumer mains, the metering or the service connection.
Who pays to replace a submain in a unit block?
In NSW strata, a submain feeding more than one lot is common property, so the owners corporation pays and the cost comes out of levies. A cable serving only your lot is your responsibility even where it runs through a common property wall. What the cable feeds decides it, not where it runs.
Can a submain run underground to a shed or granny flat?
Yes, and it is the normal way to feed a detached building. The cable has to be rated for direct burial or run in conduit at the required depth, and the circuit needs RCD protection at the board it leaves.
The bottom line
One property, one set of consumer mains, arriving at one main switchboard. Anything running out of that board to another board is a submain. That switchboard is the line between the two, and also the line between Level 2 ASP work and standard electrical work. If a quote uses one term and you are not sure it is the right one, ask which side of the main switchboard the cable sits on. DM Electrical holds Level 1 and Level 2 ASP accreditation and works out of Brookvale across Sydney. Get in touch and tell us what you are looking at.