What size heat pump hot water system do I need?
Updated October 2026
As a rough guide, a 250 to 270 litre heat pump suits most homes of one to three people, and a 300 to 315 litre unit suits three to five. The right size also depends on how many bathrooms you use and whether everyone showers at the same time. Don't just copy the old tank size, because it may never have been right.
Quick sizing guide
| Household | Typical tank size | Typical installed price |
|---|---|---|
| 1–3 people | 250–270 L | ~$4,000 |
| 3–5 people | 300–315 L | ~$4,725 |
Prices are Perth metro supply-and-install figures from independent price guides, checked October 2026. Your exact price depends on your home and the unit, and we confirm it in writing after a site visit.
Why the size matters
An undersized system runs out partway through the evening, usually right when the last person jumps in the shower. An oversized one costs more to buy and more to run for capacity nobody uses. Getting the size right matters more than the brand.
What we look at
- How many people live in the house and how many bathrooms are in use
- Whether hot water use is bunched into one window or spread through the day
- Big users like a large bath, a rain shower head or a busy laundry
- Whether you've got solar and can heat the tank in the middle of the day
- Where the unit can sit, with enough airflow around it
Why not just match the old tank?
The old system may have been undersized from day one, or your household may have changed since it went in. Heat pumps also recover differently to electric elements and gas burners, so a straight like-for-like size isn't always the right answer. We work it out on site and explain the reasoning.
Questions
Is a 270 litre heat pump enough for a family of four?
Sometimes, if showers are spread out. If everyone showers in the same hour, a 300 to 315 litre unit is usually the safer pick. We confirm it on site.
Does a bigger heat pump cost more to run?
A bigger tank holds more hot water, so it uses a bit more to keep it hot. That's why we size it to your household rather than just going big.
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Free quote within 24 hours. One all-in price, agreed before we start.
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