What Size Hot Water System Do I Need Calculator
Work out what size hot water system you need. Answer a couple of questions about your household and system type, and the calculator returns a recommended capacity (litres for storage), then prices it.
Your what size hot water system do i need details
Storage systems are sized by litres; continuous-flow systems by flow rate.
Continuous-flow systems never run out, so they can be sized a little smaller.
Below the typical range for this service.
An undersized tank runs out of hot water; an oversized one wastes energy keeping water you do not use hot. Size it to your household and when you use hot water most.
Where the money goes
Estimated breakdown for your configuration
💰 Ways to save
- Heat pump and solar systems cost more upfront but far less to run, and attract rebates.
- Continuous-flow systems suit smaller spaces and never run out, so can be sized tighter.
How we estimate this
A household of 3–4 typically needs a 250–315L storage system (or a continuous-flow unit) in 2026, costing roughly $1,100 to $5,000 supplied and installed depending on type. Larger households need more capacity.
Pricing reviewed: October 2026.
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Pricing reviewed October 2026. Indicative Australian costs, not a quote.
Understanding what size hot water system do i needs in Australia
A household of 3–4 typically needs a 250–315L storage system (or a continuous-flow unit) in 2026, costing roughly $1,100 to $5,000 supplied and installed depending on type. Larger households need more capacity.
Size storage systems by litres and household size; continuous-flow systems by flow rate. An undersized tank runs out of hot water, while an oversized one wastes energy keeping unused water hot.
Frequently asked questions
What size hot water system do I need?
A 1–2 person home suits ~125–170L storage; a 3–4 person home ~250–315L; 5+ people need 315–400L or continuous flow. Size up if everyone showers at once.
Is a bigger hot water system better?
No, an oversized tank wastes energy keeping unused water hot, while an undersized one runs out. Size it to your household and peak demand.
Are you a solar / trades business?
Everyone on this page is working out what what size hot water system do i need costs because they are ready to hire. Put your business right beneath the calculator, in your state, so you are who they find. From $50/mo.