How to Choose a Geyser: 150L vs 200L, Element Wattage & Insulation
10 June 2026 · Plumbers On Duty Editorial
Most South Africans pick a geyser by price alone and live with the consequences for 10 years. Three decisions matter more than brand: tank size, element wattage and insulation class.
Tank size: matching capacity to household
| Household | Recommended size |
|---|---|
| 1 adult, 1 bathroom | 100L |
| 2 adults, 1 bathroom | 150L |
| 2 adults + 2 kids, 1–2 bathrooms | 150L – 200L |
| 4 adults, 2 bathrooms | 200L – 250L |
| Family with bath-heavy users (kids, teens) | +50L on guideline |
| Home office / WFH with daytime showers | +50L on guideline |
Oversize, not undersize. An undersized geyser runs out mid-shower; an oversized geyser costs a few extra rand per month in standing losses.
Element wattage: faster heating vs DB load
| Element | Reheat time (150L from 25→65°C) | Use when |
|---|---|---|
| 2 kW | ~3 hours | Standard DB capacity, off-peak heating |
| 3 kW | ~2 hours | Default for most SA homes |
| 4 kW | ~1.5 hours | Solar/heat-pump backup, large families |
| 6 kW (three-phase) | ~1 hour | Commercial/guest house |
A 3kW element on a 20A DB circuit is the SA default for good reason. Going to 4kW often requires DB upgrade — verify with an electrician first.
Insulation class: the hidden running-cost decider
Look at the SANS 151 energy class on the label:
| Class | Standing loss (24h) | Annual cost (R)* |
|---|---|---|
| A (best) | 0.7 kWh | ~R900 |
| B | 1.0 kWh | ~R1,300 |
| C (cheap units) | 1.5 kWh | ~R1,950 |
| D (no longer compliant) | 2.0+ kWh | ~R2,600 |
*Assumes R3.50/kWh, geyser always energised.
Choose Class A or B. The R800–R1,500 premium over a Class C unit pays back in under 18 months.
Other features worth paying for
- Element accessibility — a flange-mounted element costs R400 more upfront, saves R1,500 every element replacement.
- Drip tray with float switch — alerts you to a leak before it floods. R150–R350 add-on.
- Smart timer / WiFi control — programmable on/off can save 20–30% on standing losses. R1,200–R3,500 add-on.
What you don't need
- Stainless tanks unless you're on borehole with high chloride
- 6 kW elements in a single-phase home
- "Hyperboost" / "Quickheat" marketing labels — meaningless
See typical geyser replacement costs and the repair vs replace decision tree.