How do I calculate the right heat pump size?
Start with roughly 50 litres of tank capacity per person per day, then adjust for how your household actually uses hot water. That rule of thumb covers normal showers, kitchen and laundry use. Push the size up if you have teenagers, a large bath that gets used, back-to-back morning showers, or plans for the household to grow. You can trim it down for a genuinely low-use household, but the penalty for undersizing, cold showers, is worse than the penalty for one size up, which is a slightly larger tank doing the same job comfortably.
| Household | Suggested tank size | Notes |
|---|---|---|
| 1 to 2 people | 200L | Covers a couple with normal use |
| 3 to 4 people | 250 to 300L | The most common family size we install |
| 5 or more people | 300L or twin systems | Size up, especially with teenagers |
Why does sizing matter more for heat pumps than electric storage?
Heat pumps recover more slowly than a resistive element, so the tank has to carry you through peak use. A conventional electric storage unit can brute-force reheat with a 3.6kW element. A heat pump heats gently and efficiently, which is the whole point, but it means that once the tank is empty you wait longer for hot water. The fix is not a bigger compressor, it is the right tank. This is why the 200 to 300L range dominates family installations, and why we ask about shower habits before we quote rather than after you have run out.
What does a heat pump cost installed on the Gold Coast?
As of 2026, a quality heat pump installed on the Gold Coast costs $2,500 to $4,500 after rebates, with rebates typically worth $1,000 to $2,500 depending on the unit and the incentives current at install time. Small-capacity Energy Efficiency Certificates and other schemes move around, so we confirm the exact rebate position when we quote. For comparison, an electric storage system runs $1,300 to $2,400 installed, gas storage $1,800 to $3,200, and gas continuous flow $1,900 to $3,500. The heat pump costs more upfront than plain electric storage but uses roughly a quarter to a third of the electricity, and paired with rooftop solar and a timer it is the cheapest hot water to run on the Gold Coast.
Does the Gold Coast climate suit heat pumps?
Yes, South East Queensland is close to ideal heat pump territory. A heat pump moves heat from the surrounding air into the water, so mild air temperatures year-round mean strong efficiency in every season. The cold-climate performance problems you may read about in reviews from Victoria or Tasmania are largely irrelevant here. Two local factors do matter: placement, because the units have a fan and are best positioned away from bedroom windows, and coastal air, so we choose units and positions with corrosion in mind for properties near the surf.
Can I replace my old electric system with a heat pump?
Usually yes, and it is the most common changeover we do, because a heat pump uses the same plumbing connections as the electric storage tank it replaces. Most swaps are completed in a day, and hot water is back the same evening, though heat pump first heat-up is slower than an element. Things we check at quote stage: the tempering valve, which must deliver no hotter than 50 degrees to bathroom fixtures under AS/NZS 3500.4, the drain arrangement for the relief valve, physical access for a tank that may be taller than the old one, and airflow around the unit. All hot water installation work in Queensland is licensed work, and we certify every install under QBCC licence 15243081.
What happens if I undersize or oversize?
Undersizing means cold showers and an overworked unit, while oversizing mostly just costs a little more upfront. An undersized heat pump runs longer, recovers slower than the household drains it, and the family learns the shower roster the hard way. An oversized one cycles less and always has reserve, at the cost of a couple of hundred dollars more and a bigger footprint. When a household sits between sizes, we size up, and we would rather lose a sale than install a 200L unit for a family of five.
Ready for cheaper hot water? Call Hills Plumbing & Gas on 0472 657 042. We size the system to your household, quote a fixed installed price including rebates, and certify everything under QBCC licence 15243081. See our hot water systems service.