First, define what the system has to do
Write down how many showers run at once, whether a bath is used regularly and when the household needs most hot water. Tell the installer if the current system runs short or if the household is changing. Those details are more useful than bedrooms alone.
The system planning tool turns your answers into an enquiry brief. Read the heat pump guide and gas system guide for the specific installation questions behind each option.
Compare the way heat is supplied
A heat pump uses electricity to transfer heat from the surrounding air into stored water. Gas systems use gas, with storage and continuous-flow options. Those different approaches affect space, capacity, recovery and the pattern of energy use.
The Australian Government's hot-water system overview describes the main system categories. It provides a starting point, but the proposed model's documentation and the property assessment determine how an installation should be planned.
Look at the location before choosing the model
For a heat pump, ask about airflow, clearances, condensate drainage, access for maintenance and sound near bedrooms or neighbours. Check the proposed location against the manufacturer's requirements. A narrow service area can change which options are suitable.
For gas, ask the installer to check supply and the appliance's installation requirements. Continuous-flow sizing involves simultaneous flow and temperature rise. A nominal flow figure doesn't, by itself, prove that the unit will meet every household scenario.
Put required plumbing, electrical or gas alterations into each quote. Otherwise a lower headline can simply describe less of the job.
Make running-cost assumptions visible
Ask which tariff, hot-water usage and operating schedule underpin any estimate. If you have rooftop solar electricity, ask how heating would be scheduled and what generation is actually available after other household uses.
The Government's smart-home guidance discusses scheduling hot-water heating. An installer and your retailer can explain the practical controls and tariff arrangement for your home. Don't assume daytime operation or an advertised saving is automatically appropriate.
If you'll keep gas for cooking or another appliance, include that when comparing ongoing costs. If the plan involves leaving gas entirely, ask for any required disconnection work to be identified. Avoid a savings comparison that silently assumes a different household setup.
Compare support after installation
Ask who services the proposed model, how warranty work is arranged and what routine maintenance is required. For a heat pump, confirm the arrangements for any specialist electrical or refrigerant work. Product cover and installation workmanship aren't always handled by the same party.
The right decision should come with an explanation of the model, capacity, site conditions and complete installed scope. Use the cost guide to compare the written proposals and the rebate guide to clarify any incentive assumptions.
You can request a replacement enquiry without committing to a system type. State that you'd like both options explained against the same household brief.