Quick answer
Size on simultaneous demand, not on bedrooms. As a working guide: 150L suits two adults, 200L suits three to four, and 250L suits four or more or any household that runs a bath and a shower at the same time. Oversizing costs you standing heat losses every day of the year; undersizing gives you cold showers every morning. The deciding question is how many hot outlets run at once at your busiest time.
What you can do now
- 1Count your peak simultaneous hot-water draws — the 7am reality, not the average
- 2Add capacity if you have a bath that gets used, since a single bath draws far more than a shower
- 3Check the roof space or cupboard will physically take the larger cylinder and its drip tray before deciding
- 4Confirm the existing circuit and isolator suit the element rating of the size you are moving to
- 5Consider a timer or a heat pump if the driver is cost rather than capacity
When to call a professional
Ask your plumber to size the geyser on fixture count and peak simultaneous demand rather than bedroom count, and to confirm the structure, drip tray and electrical circuit all suit the size you choose. Going up a size is not just a bigger cylinder — the brackets, tray and sometimes the circuit change with it, and that belongs in the quote.
Typical cost in Johannesburg
150L R7,500 · 200L R9,500 · 250L R12,000 fitted
Indicative ranges only. We provide written, itemised quotes before any work.
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