Heat Pump Hot Water Savings Calculator Australia
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Compare the running cost and lifetime savings of a heat pump hot water system against your existing gas, electric or off-peak hot water — with STCs and state rebates (VEU in Victoria, ESS in NSW) netted off automatically. Built for Australian retail rates and 2025–26 incentive levels.
Household and current system
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Your heat pump payback
Payback period
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to recover net cost
Annual savings
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vs your current system
Net out-of-pocket
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price after STC + state rebate
Current run cost
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existing system, per year
Heat pump run cost
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new system, per year
Lifetime net (15 yrs)
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total benefit over service life
Net cumulative position (savings minus net cost)
Year-by-year savings table
| Year | Annual savings | Cumulative savings | Net position |
|---|
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How to use this calculator
- Pick the system you currently have. Electric resistive is the most expensive to run; off-peak electric and gas are mid-range; solar electric boost is the cheapest of the legacy options.
- If you're on gas and have a recent bill, enter the actual MJ/day. Otherwise leave it at 0 — the calculator estimates it from household size and system efficiency.
- Use a realistic annual-average COP. Manufacturer brochures often quote a peak COP under ideal conditions; the AS/NZS 4234 rated COP (or "STC zone-3 COP") is closer to real-world performance.
- Stack rebates. Federal STCs apply nationally; state schemes (VEU, ESS, others) layer on top. Ask your installer for an itemised quote.
Key assumptions
- Hot water demand: 4 kWh thermal per person per day, in line with AS/NZS 4234 medium-load profile.
- System efficiencies: electric resistive 100%, gas storage 65%, gas instantaneous 85%, solar electric boost ~50% grid input on average.
- Off-peak electricity priced at 65% of peak retail rate (typical Australian metropolitan ratio).
- Heat pump: 1 kWh electricity in → COP × kWh thermal out (default COP 3.5).
- Annual savings held constant across the 15-year horizon. Real-world gas tariffs have been rising faster than electricity, so the result is conservative for gas-replacement scenarios.
- Installation cost is fully captured upfront, with STC and state rebates netted off before payback maths.
Frequently asked questions
How much can a 4-person household save?
Replacing a gas storage system: typically $400–$700/yr. Replacing electric resistive: $600–$1,100/yr. Replacing off-peak electric: $200–$400/yr. Replacing solar electric boost: $100–$250/yr. Plug your numbers in above for a household-specific figure.
What rebates can I claim?
Federal STCs apply nationally and are deducted at the point of sale by accredited installers. On top of that: VIC offers $1,000–$1,400 via Victorian Energy Upgrades; NSW offers $300–$640 via the Energy Savings Scheme; SA and ACT have separate programs. Always ask the installer to itemise every rebate on the quote.
Should I install a heat pump if I have solar panels?
Yes — and run it during the day. A timer-set heat pump pulls 1 kWh of electricity to deliver 3.5 kWh of hot water; if that 1 kWh is solar you'd otherwise have exported at 5 c/kWh, the operating cost approaches zero. Pair this calculator with our solar payback calculator for a full picture.
What's the difference between brochure COP and real-world COP?
Brochure peak COP is measured at 20°C ambient and a small temperature lift. Real-world annual COP is lower because air and water-tank temperatures vary across seasons. Use the AS/NZS 4234 rated COP, or the "Zone 3" / "Zone 4" figure on the rebate paperwork — that's the number installers and rebate calculators use.
Heat pump or solar hot water — which is better in 2026?
Heat pumps have largely overtaken thermosiphon solar hot water for new installs. They're cheaper to buy, simpler to plumb, and pair better with rooftop PV (you let your panels charge the heat pump rather than a separate solar collector). Existing solar hot water systems in good condition are still worth keeping — just service annually.
Can I disconnect gas entirely?
If hot water is your last gas appliance, yes — switching it electric lets you cancel the daily gas supply charge (typically $250–$400/yr in 2025–26). The calculator only models running cost; if you can disconnect gas, add the supply charge to your annual savings for a more accurate result.
Related calculators and reading
Solar Payback Calculator
Model the payback period and 25-year lifetime savings of a rooftop solar system. Solar makes heat pump hot water nearly free to run during the day.
Run solar payback →Home Battery Payback Calculator
If you're already converting hot water to electric, model how a battery captures your evening surplus and pays back across 15 years.
Run battery payback →How to reduce your electricity bill
Article — the highest-impact moves Australian households can make in 2025–26, including how heat pumps, solar and timers stack.
Read article →This calculator provides general estimates only and is not financial, energy or product advice. Rebate values are indicative and change frequently — always confirm current STC and state rebate amounts with an accredited installer before purchasing.