Pairing a heat pump hot water system with solar panels is one of the smartest energy upgrades an Australian homeowner can make. Hot water typically accounts for 20–30% of a household's electricity bill — and a heat pump hot water system with solar panels can slash that cost to near zero. Here's exactly how the combination works, what it saves, and how to set it up correctly.
Why Heat Pump Hot Water and Solar Are a Natural Fit
A heat pump hot water system uses electricity to run a compressor — similar to a reverse-cycle air conditioner — to extract heat from the surrounding air and transfer it to water. They're 3–4 times more efficient than a conventional electric resistive element: one unit of electricity produces three to four units of heat energy.
This is particularly powerful when that electricity comes from solar panels. During a sunny day, your panels may generate significantly more power than your household needs. Without a heat pump hot water system, that excess typically gets exported to the grid for 5–10c/kWh. With a heat pump, you can divert that surplus into heating your hot water tank instead — effectively storing solar energy as hot water.
How Much Electricity Does a Heat Pump Hot Water System Use?
A modern heat pump hot water system (250–315L tank, which suits most Australian families) typically draws 500–900 watts while running. With a Coefficient of Performance (COP) of 3–4, it uses approximately 1.0–1.5 kWh of electricity to produce the equivalent of 3–5 kWh of heat.
Over a full day, a heat pump hot water system for a family of four typically consumes 1.5–3.0 kWh of electricity — colder regions push that a little higher, as covered in our guide to heat pump hot water in cold climates. At a grid rate of 30c/kWh, that's 45–90c per day, or $165–$330 per year — already much cheaper than a gas or resistive electric system.
| Hot Water System Type | Annual Energy Cost (4-person household) |
|---|---|
| Gas storage (mains pressure) | $400–$600 |
| Electric resistive element | $700–$1,100 |
| Heat pump (grid-powered) | $165–$330 |
| Heat pump (solar-powered) | $0–$80 |
The Solar Savings: Real Numbers
If you have a 6.6kW solar system generating an average of 26 kWh per day (typical in Queensland), your heat pump only needs to draw 1.5–3 kWh of that — easily covered by midday solar surplus. The savings depend on what you'd otherwise be paying:
- Replacing a gas hot water system: Eliminates $400–$600/year in gas costs, plus you remove the daily gas supply charge ($300–$400/year if gas is disconnected). Total saving: $700–$1,000/year.
- Replacing a resistive electric system: The heat pump uses 65–75% less electricity, and when powered by solar that cost drops to near zero. Saving: $600–$1,000/year.
- Running cost on solar vs grid: If you time your heat pump to run midday (when solar is generating), the effective electricity cost is $0 instead of 30c/kWh — saving $165–$330/year just on the hot water electricity.
Timer Settings: The Key to Maximising Solar Use
The biggest practical step to align your heat pump with solar generation is setting its timer to run during peak solar hours. Most heat pump systems allow timer scheduling via a controller or app. Aim for:
- Start time: 10am–11am (solar well established)
- Duration: 2–4 hours (enough to fully heat a tank)
- Winter adjustment: Start slightly earlier (9am) as the pump may need longer in colder weather
Some advanced systems support "solar divert" modes, similar to EV chargers, where the heat pump is automatically triggered when excess solar generation is detected. Systems from brands like Reclaim Energy support this via compatible solar inverter integrations.
State Rebates That Make This Combination Even Cheaper
Both solar panels and heat pump hot water systems attract government rebates in Australia, and you can claim both:
- Solar STCs: Reduce upfront solar cost by $2,500–$4,000 for a 6.6kW system
- Heat pump rebates (federal STCs): Reduce the cost of a heat pump hot water system by $600–$1,000
- State-specific rebates: Victoria's Hot Water Rebate offers up to $1,000. NSW PDRS provides point-of-sale discounts. SA and QLD also have rebate schemes that can further reduce costs.
In a state like Victoria, combining all available rebates, a heat pump hot water system (normally $3,500–$4,500 installed) could cost as little as $1,500–$2,500 out of pocket.
Performance in Cold Climates
Heat pump hot water systems are slightly less efficient in cold weather, as there's less ambient heat to extract from the air. In Melbourne or Canberra winters, a heat pump's COP may drop from 4 down to 2.5–3. This means it uses more electricity — but it still runs, and at 30c/kWh grid cost, it's still far cheaper than a resistive element.
For alpine areas and very cold climates (Snowy Mountains, Orange, Ballarat, Tasmania highlands), models with a "Boost" resistive element can ensure hot water even on very cold nights. Just ensure the boost element is set to only activate when the heat pump can't keep up, not as a default.
Calculate Your Combined Savings
The exact savings from pairing a heat pump hot water system with solar depend on your current hot water system, household size, location, and how much daytime solar surplus you have. Use our Heat Pump Hot Water Savings Calculator to model the full picture — including the combined effect of solar panels offsetting your heat pump's electricity use and eliminating your gas supply charges if you disconnect gas entirely.