Guide · services
Water, sewer and power, priced and explained.
What connecting a granny flat costs, the shared-services rule most buyers have never heard of, and what quietly moves the number.
Connecting a suburban granny flat typically costs $5,000 to $20,000 across water, sewer, power and stormwater. Nearly every council requires shared connections with the main house: one meter, one driveway, sub-metering for tenants. Rural blocks swap sewer for septic at $8,000 to $18,000.
The short version
Services are the least visible cost in a granny flat project and the second most variable after the crane. Suburban blocks with town water, sewer and power nearby typically spend $5,000 to $20,000 connecting. Rural blocks trade sewer for septic and can add tanks and pumps. Almost every council requires the granny flat to share the main house’s connections, which shapes the whole design.
The shared-services rule
Councils keep secondary dwellings secondary: one water meter, one power connection, one street number, one driveway, shared with the primary dwelling. Moreton Bay writes it into approval conditions explicitly. Practically this means your granny flat tees off the house rather than getting its own meters, and separate billing for a tenant is handled with private sub-meters, not utility accounts.
Each service, priced
| Service | Typical cost | Notes |
|---|---|---|
| Water | $1,000–$4,000 | Tee off the house line; distance is the cost |
| Sewer | $2,000–$8,000 | Gravity if the falls allow, pump if not; build-over-sewer approvals where lines run close |
| Septic (rural) | $8,000–$18,000 | Where no town sewer; treatment system plus irrigation area |
| Power | $1,500–$6,000 | Sub-main from the house board; board upgrades are the wildcard |
| Stormwater | $500–$3,000 | Roof water to the kerb or lawful point |
| Service location survey | $1,500–$2,200 | Find everything before designing; ours invoiced $2,200 |
What decides your number
- Distance: every metre of trench is money. Siting the granny flat near the existing services run is worth more than most finish upgrades.
- Falls: sewer wants gravity. A block that falls away from the street may need a pump well, a few thousand extra.
- The switchboard: older homes with full boards need upgrades before a sub-main goes in. Get the sparky’s opinion early.
- Sewer easements: building near mains triggers build-over-sewer rules; our Brisbane job carried that approval and the clearances shaped the siting.
Every plumbing and electrical connection is licensed-trade work with compliance certificates: an owner-builder coordinates it but does not do it. Connection points and requirements are documented in your drawings, and the service location report we price into approvals finds everything before anyone designs over the top of a main.
Straight answers
Can my tenant have their own power bill?
Not a separate utility account in most councils; the connection is shared with the house by approval condition. A private sub-meter measures their usage and you bill on it, which is standard practice for granny flat rentals.
What if my block has no sewer?
A septic or treatment system replaces it, $8,000 to $18,000 with its irrigation area, and it needs its own council approval. Common and routine on acreage.
Who does this work?
Licensed plumbers and electricians only; compliance certificates go to the certifier. Siting the dwelling close to existing runs is the single best way to spend less here.
Where this lands on price
Every price, every way to buy, on one page.
Kit $59,900 to finished and installed, with the all-in number printed.