Sydney conditions that shape the choice
Hardness of about 57 mg/L
That's Sydney Water's figure for Greater Sydney's drinking water, measured as calcium carbonate. The drinking water guideline that exists to limit scale in hot water systems sits at 200 mg/L.
A third of homes are units
Flats and apartments made up 30.7% of Greater Sydney's occupied homes at the 2021 Census. NSW strata rules class installing or replacing a heat pump as a minor renovation, which needs approval before work starts.
More than a third rent
35.9% of Greater Sydney's occupied homes were rented in 2021, above the NSW figure of 32.6%. If you rent, tell the landlord or agent as soon as the system starts failing, rather than on the morning it stops.
Frosty mornings out west
Camden Airport's average July minimum is 3.1°C, against 8.1°C at Observatory Hill. A heat pump heats water using the outside air, so in the south-west ask how a model performs on the coldest mornings.
What NSW sets, and what it leaves to you
Building Commission NSW requires a temperature control device whenever a hot water heater is replaced, whatever its type or location. An identical model is no exception; only replacing the solar collector panels on their own is.
That device keeps water at showers, baths, handbasins and bidets to 50°C, while the tank itself stores hotter water. The Australian Building Codes Board explains why: Legionella growth is reduced significantly at 60°C and above, so turning the thermostat down isn't the safe fix.
Swapping an existing system is listed as minor work, so no Notice of Work goes in before the plumber starts. Sydney Water still counts a hot water replacement as a job for a licensed plumber, and says to ask for the Certificate of Compliance when it's done.
The usual options in a Sydney home
| Help toward the cost in NSW | Ask before you buy | |
|---|---|---|
| Heat pump | Can attract an Energy Savings Scheme discount, plus small-scale technology certificates (STCs) if the model is on the Clean Energy Regulator's register and under 425 L | In a unit, has the owners corporation approved it? Where will the unit sit, and how does it run on a cold morning? |
| Solar water heater | Possibly an Energy Savings Scheme discount, plus STCs for registered models under 700 L | Who will do the roof work, and is the booster electric or gas? |
| Gas or electric, storage or continuous flow | None covered here | For gas, does the installer hold a gasfitting licence, and will you get the gas certificate as well? |
The Energy Savings Scheme, read carefully
Energy NSW calls it a discount, not a rebate. Its published figures, up to $640 when a heat pump replaces an electric water heater and up to $330 when it replaces gas, are marked indicative only. They come from a page updated on 6 February 2026, and the scheme's rules changed again on 7 September 2026.
You always make a minimum payment toward the system and its installation. Installers must partner with an Accredited Certificate Provider, and they work independently of the NSW Government, so be wary of anyone who sounds official. More on our NSW discounts page.
Questions for a Sydney hot water plumber
- Is the tank itself leaking, or is this a part you can replace?
- Which Accredited Certificate Provider are you partnered with, and where is the discount shown on the quote?
- Will you fit the temperature control device and give me the Certificate of Compliance?
- For a unit: what plans and details will the owners corporation need from you?
What we would do
Decide on the next system while the current one still works: type, size and where it will go. If you're in a strata building and want a heat pump, get the approval moving now, because a dead tank won't wait for a strata meeting. When you get quotes, ask for one written price that shows the full cost, every discount and what you pay, and treat any NSW figure you've read as a guide only.