What Size Hot Water System Do I Need?
When it comes to hot water systems, size really does matter! While it might seem easiest to replace your old unit with the same size, it’s always worth taking a step back to assess your household’s current hot water needs. The right-sized system will save you money, improve efficiency, and make sure no one ends up with a cold shower.
Why Does Size Matter?
A system that’s too small will struggle to keep up with demand - especially during peak times like busy mornings. Constantly running out of hot water isn’t just frustrating, it can put unnecessary strain on your system.
On the flip side, a system that’s too large may seem like a safe bet, but it can be a drain on your wallet. Larger tanks use more energy to keep water hot - even when you’re not using it - which means higher energy bills for no added benefit.
💡 The goal is to find a system that comfortably meets your needs, without paying for more than you use.
What Size Do I Need?
Sizing depends on a few key factors:
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Number of people in your household
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Number of bathrooms/showers
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Shower habits (length, timing, and showerhead type)
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Whether you use hot water for laundry or dishwashing
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Peak usage times (e.g., everyone showering before school or work)
Typical System Sizes by Household
Here’s a general guide based on average Australian household usage:
Electric Hot Water Systems
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Continuous system (heats water on demand):
4-person household: ~160 litres -
Off-peak system (heats overnight, stores for next day):
4-person household: 250–315 litres
Gas Storage Systems
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Efficient and quick to reheat
4-person household: ~170 litres
Heat Pump Systems
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Energy-efficient alternative to electric
4-person household: 270–315 litres
📌 These are just averages. If your household uses multiple showers at once or prefers long showers, you may need a larger unit.
Electric hot water system
| Number of people | Peak usage | Tank size |
| 5 – 8 | High | 400 |
| Low | 250 | |
| 3 – 6 | High | 315 |
| Low | 160 | |
| 2 – 4 | High | 160 |
| Low | 125 | |
| 1 – 3 | High | 125 |
| Low | 80 |
Gas or LPG hot water system
| Number of people | Peak usage | Tank size |
| 5 – 8 | High | 340 |
| Low | 170 | |
| 3 – 6 | High | 260 |
| Low | 160 | |
| 2 – 4 | High | 160 |
| Low | 135 | |
| 1 – 3 | High | 135 |
| Low | 90 |
Need Help Choosing?
At Hot Water Boss, we’ll help you work out your peak hot water usage and recommend the right size system for your home and lifestyle. Whether you’re upgrading or replacing an old system, we’ll make sure you get the perfect fit - no more guesswork, no more cold showers. And don't forget, we offer free, fixed price all-inclusive quotes on system replacement with installation for Jimboomba, Logan, Brisbane, Gold Coast, Redlands (mainland), and Scenic Rim!
