Electrical Connections for Duplexes and Granny Flats in the Inner West: What You Need to Know

How do electrical connections work for duplexes and granny flats? A duplex usually needs separate metering and a separate main switch for each dwelling, and if the lots will be subdivided, each lot should have its own network connection. A granny flat is normally supplied from the main house through a new sub board, with the option of a private sub-meter or a separate retail meter. Getting a Level 2 ASP involved at the design stage avoids costly changes once construction has started.

⚡ Quick Answers: Duplex and Granny Flat Connections

• Does a duplex need two connections? Usually two meters and two main switches; two separate connections if it will be subdivided.
• Does a granny flat need a new connection? Usually not. It's normally fed from the main house supply via a sub board.
• Can a granny flat have its own meter? Yes, either a private sub-meter or a separate retail meter.
• Will I need three-phase? Only if the combined load calculation says so, often driven by EV chargers and electrification.
• Who handles the network side? A Level 2 ASP, including the Ausgrid application and connection.
• When should I plan it? Before the plans are finalised.

1. Duplexes: two dwellings, two installations

A dual occupancy duplex is two separate homes, so each needs its own electrical installation: its own main switch, safety switches, metering and switchboard. The key question is whether the duplex will be strata or Torrens subdivided. If it will, each lot should have its own connection to the network so one owner's supply doesn't run through or depend on the other lot. That usually means two consumer mains runs and two meter positions, planned from the start. Retrofitting a second connection after the building is finished is far more disruptive.

2. Granny flats: usually one supply, a new sub board

In NSW, a secondary dwelling generally can't be separately subdivided from the main house, which is why most granny flats are supplied from the existing property connection. The usual setup is submains from the main switchboard to a new sub board in the granny flat, with its own main isolator and safety switches. The main house's supply, consumer mains and switchboard need to be able to carry the combined load, which is where older Inner West terraces often need an upgrade first.

3. Metering options

• Shared meter: simplest and cheapest, with costs split privately. Rarely ideal for a rented granny flat.
• Private sub-meter: tracks the granny flat's usage for internal cost sharing on the one retail account.
• Separate retail meter: the granny flat is billed directly by its own retailer. Costs more to set up but keeps tenancies clean.

Duplexes almost always use separate retail meters, one per dwelling.

4. Capacity: single-phase or three-phase?

Two all-electric households with induction cooking, heat pump hot water, ducted air conditioning and EV chargers can add up to a substantial combined demand. A maximum demand calculation under AS/NZS 3000 shows whether single-phase supplies are enough or whether three-phase makes sense. For a duplex, each dwelling can have its own single-phase or three-phase supply. For a granny flat, the question is whether the main house supply can carry both. Our guide to single-phase vs three-phase consumer mains explains the difference.

5. Cable routes on narrow Inner West blocks

Many Inner West duplex and granny flat sites are narrow, with limited side access, shared driveways and rear lanes. The cable route from the connection point to each meter position, and from the main board to a rear granny flat, needs to be worked out on site. Our guide to granny flat electrical connections on narrow Inner West blocks goes into the access challenges in detail.

6. The connection process

1. Site assessment and load calculation during design.
2. Meter positions and cable routes shown on the plans.
3. Connection application to Ausgrid for any new or altered connection.
4. Temporary builders supply during construction if needed.
5. Consumer mains, switchboards and sub boards installed.
6. Notification of Service Work, meters installed by the retailer's metering provider, and a Certificate of Compliance for Electrical Work.

If your build starts on temporary power, our guide to moving from temporary builders supply to a permanent connection covers the handover.

How High Demand Electrical helps

We're a Level 2 ASP team (Licence 397193C) that works with Inner West owners, builders and designers on duplexes and granny flats from the design stage. We calculate the load, plan meter positions and cable routes, lodge the Ausgrid application, install consumer mains and boards, and certify the finished job.

Duplex and Granny Flat Connection FAQs (Inner West)

Does each side of a duplex need its own power connection?

Usually yes, and always plan for it if the duplex will be subdivided. Each dwelling generally needs its own metering and main switch, and separately titled lots should each have their own connection so one lot's supply doesn't rely on the other.

Can a granny flat have its own electricity meter?

Yes. A granny flat can be fed from the main house supply with a private sub-meter, or have a separate retail meter so it's billed independently, which suits rented granny flats.

Will I need three-phase power for a duplex?

Not always. It depends on the combined maximum demand, especially with EV chargers, heat pumps and induction cooking. A load calculation shows whether single-phase supplies are enough.

When should I bring in a Level 2 ASP?

At the design stage, before plans are finalised, so meter positions, cable routes and the connection application are sorted before construction starts.

Can a granny flat be subdivided in NSW?

Generally no. Secondary dwellings in NSW usually can't be separately subdivided, which is why most granny flats are supplied from the main dwelling rather than a separate network connection.

Plan Your Duplex or Granny Flat Connection

Designing a duplex or granny flat? Get a consumer mains and connection quote or call 0402 559 777. We'll help you lock in the electrical design before the builder starts.