Buying Guide
What Size Hot Water Cylinder Do I Need?
4 minute read
Cylinder sizing is not just about litres. Two systems with the same capacity can perform very differently depending on how fast they reheat and how your household uses hot water.
Start with peak demand
The critical question is not how much hot water you use in a day, but how much you use in your busiest hour — typically consecutive morning showers, sometimes with laundry running at the same time.
General guidance
As a broad starting point, smaller households are often served by cylinders in the 135–180 litre range, mid-sized families by 180–250 litres, and larger households by 250–300 litres or more. These are indicative only.
Your installer will size the system properly based on occupancy, fixtures, usage patterns and the recovery rate of the specific model.
Why oversizing isn't free
A larger cylinder takes more space, costs more, and carries slightly higher standing losses. The goal is a system correctly matched to the household, not the biggest one that fits.
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Sizing should be confirmed on site by a qualified professional.
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