Over 100A Three Phase in Sydney: The Ausgrid Approval Process Explained

If your Sydney property sits in Ausgrid territory — the eastern suburbs, inner city, north shore, or northern beaches — and you need more than 100 amps per phase, you can't just order a bigger switchboard and get on with it. Anything above 100A per phase triggers a formal network approval process with Ausgrid, and skipping a step usually means a rejected application, a delayed switchboard, or a defect notice after the work is done.

Here's the process, start to finish, for homes, apartment buildings, commercial fitouts, and developments in Ausgrid's network that need a supply upgrade beyond 100A three phase.

Why 100A is the line in the sand

Under the Service and Installation Rules of NSW, any main switchboard rated above 100 amps per phase requires the network distributor to review and approve the switchboard design before it's built. For Ausgrid, that means submitting the Ausgrid Switchboard Compliance Statement, main switchboard plans, and a single line diagram through the Ausgrid connections portal. Ausgrid's technical standard NS114 sets out what the board needs to look like before it's accepted.

This affects strata buildings adding EV chargers, commercial kitchens, office fitouts, warehouses, and larger homes running pools, ducted air conditioning, and induction cooking off the one board.

Step 1: Establish the actual maximum demand

Before Ausgrid will look at anything, you need a number: how many amps per phase does the site actually need? For a new build, a Level 3 ASP designer calculates this using AS/NZS 3000 Appendix C — adding up lighting, socket outlets, cooking, hot water, air conditioning and EV charging loads, then applying diversity factors, since not everything runs at once.

For an existing building, a calculated figure is often overly conservative. This is where power logging earns its keep: a Fluke or Dranetz logger sits on the switchboard for one to four weeks and records what the site actually draws, phase by phase. Many buildings that look maxed out on paper have real spare capacity once you measure it — and the reverse is also true. Ausgrid will accept either a calculated figure for new work or a measured figure with supporting data for existing sites, but you need one before you go further.

Step 2: Check whether the street has capacity

The next question isn't about your switchboard — it's about the transformer and street mains feeding your property. Ausgrid needs to confirm the local low-voltage network can actually deliver the extra load. If the transformer is already heavily loaded, or the street cabling is undersized for your new demand, Ausgrid may require network augmentation works before your connection can proceed, which changes both the cost and the timeline. This capacity check happens as part of the application, and it's the step most homeowners and builders don't budget time for.

Step 3: Submit the connection application

With a maximum demand figure in hand, the application goes to Ausgrid through the connections portal. For anything beyond a basic residential upgrade, this is typically managed by a Level 2 ASP electrician working alongside a Level 3 ASP designer, since the application needs supporting technical documentation, not just a form.

Step 4: Design and submit the switchboard

A Level 3 ASP designer prepares the main switchboard design to NS114 — protection settings, metering arrangement, busbar ratings, and physical layout — and the Ausgrid Switchboard Compliance Statement is completed and lodged with the design pack.

Step 5: Get switchboard design approval

Ausgrid reviews the submission against NS114 and the Service and Installation Rules. Common rejection reasons include missing single line diagrams, incorrect fault level ratings, and metering compartments that don't match Ausgrid's current specification. Getting this right the first time is the single biggest lever on how long the whole project takes — a rejected design pack can add two to four weeks.

Step 6: Installation

Once the design is approved, the physical work happens: the new switchboard is manufactured to the approved design, installed, and connected. Depending on scope this covers consumer mains, metering, and any network-side connection work carried out by a Level 1 ASP electrician.

Step 7: Inspection

Ausgrid or its appointed inspector checks the completed switchboard and installation against the approved design before energisation. This is a physical, on-site inspection — not a paperwork exercise — and it picks up anything that drifted from the approved drawings during construction.

Step 8: Testing

Protection settings, earthing, insulation resistance, and metering accuracy are tested and recorded. For larger commercial and multi-tenancy sites this also confirms load balancing across phases is within acceptable limits.

Step 9: Commissioning

The connection is energised, metering is confirmed live and reporting correctly, and the site is formally handed over. From here it's a working, compliant connection recognised by Ausgrid.

How long does this take with Ausgrid?

For a straightforward residential or small commercial upgrade with a clean application, budget four to eight weeks from application to commissioning. Sites needing street-level augmentation, or with a rejected first-round switchboard design, can run considerably longer — which is exactly why getting the max demand figure and switchboard design right the first time matters.

Where projects usually get stuck

• Submitting an application without a proper maximum demand calculation or power log, so Ausgrid can't assess the request.
• A switchboard design that doesn't match NS114 — wrong fault ratings, missing metering provisions, or an incomplete compliance statement.
• Assuming the street has spare capacity without confirming it, then discovering augmentation works are required midway through a build program.
• Treating the >100A threshold as a formality rather than a full design-and-approval process.

HDE manages the full Ausgrid connection process

High Demand Electrical is Level 1, Level 2 and Level 3 ASP accredited, so we can run this process end to end in Ausgrid's network — from the initial power logging or max demand calculation, through switchboard design and Ausgrid approval, to installation, inspection, testing and commissioning.

If you're planning a supply upgrade beyond 100A three phase in an Ausgrid area — for an apartment building, commercial fitout, or larger home — get in touch and we'll scope the application before you commit to hardware.