How big a hot water system do I need?
Get the size wrong and you'll either run out of hot water every morning or pay to heat water you never use. The right size depends on how many people live in the house, how many bathrooms you have, the type of system, and when you all use hot water. Here's a plain guide to sizing, and the questions we ask before recommending a system.
What decides the size
People in the house
More people means more showers, washing and dishes. It's the biggest factor.
Bathrooms used at once
Two showers running at the same time need much more hot water per minute than one.
Type of system
Electric, gas and heat pump storage tanks recover at different speeds, and continuous flow systems are sized by flow rate rather than litres.
Your habits
Long showers, a big bath, or everyone showering in the same hour all push the size up.
A rough guide
These are general starting points only. We size every system for the actual home.
- Electric storage: electric tanks recover slowly, so they're sized larger. Roughly 125 to 160 litres for one or two people, 250 to 315 litres for three to five, and more for larger households.
- Gas storage: gas reheats quickly, so a smaller tank goes further. Roughly 135 to 170 litres suits many families of three to five.
- Continuous flow: sized by litres per minute. Around 16 to 20 litres per minute suits one bathroom at a time; 26 litres per minute or more suits two showers running together.
- Heat pump: usually similar tank sizes to electric storage, with the recovery speed depending on the model and the weather.
Questions we ask before recommending
- How many people live here now, and will that change soon?
- How many bathrooms, and do two showers ever run at the same time?
- Do you have gas connected, and what's on your roof or side path?
- Is the current system running out, or just old?
- Where is the far bathroom? Long pipe runs affect the choice. See flow and return systems.
We'll give you two or three options that suit your home, with a fixed price for each before any work starts.
In southern Eastern Suburbs homes
Many family homes in Matraville, Pagewood, Maroubra and Botany still have a tank that was sized for a smaller household, or a small electric unit that can't keep up once the kids are teenagers. Upsizing, switching to gas continuous flow where gas is connected, or a heat pump are the usual solutions. Our hot water guide compares the types.
Why locals call us
- Local to Matraville and the southern Eastern Suburbs
- Free on-site quotes, with a fixed price before any work starts
- Lifetime labour warranty on our workmanship
- 100+ five-star Google reviews
- Licensed plumbers and gasfitters (Lic. 398171C)
Common questions
What size hot water system do I need for a family of four?
As a rough guide, around 250 to 315 litres for electric storage, 135 to 170 litres for gas storage, or about 20 to 26 litres per minute for continuous flow. It depends on your habits and bathrooms.
Is a bigger hot water system always better?
No. An oversized tank costs more to keep hot. The best system matches how your household uses hot water.
Why do electric systems need bigger tanks than gas?
Electric tanks reheat more slowly, so they need to store more hot water to get through busy times.
How do I size a continuous flow system?
By flow rate in litres per minute, based on how many hot taps and showers run at the same time.
Related help: hot water replacement, hot water guide, continuous flow hot water, heat pump hot water and hot water running out. Local pages: hot water Matraville, hot water Pagewood, hot water Maroubra and hot water Botany.