Tankless Geysers vs Traditional Geysers: Pros and Cons

Tankless (or “instant”) geysers heat water on demand instead of storing a tank’s worth at a set temperature around the clock. They’re a popular idea in Alberton and the East Rand because a smaller, wall-mounted unit sounds like an easy upgrade over a bulky roof-space tank — but the fit isn’t automatic for every home. Here’s what actually matters before switching.

How they’re different from a storage geyser

A standard geyser keeps 100-250 litres of water hot in a tank, ready whenever a tap opens. A tankless unit has no reserve — it heats water as it flows through, using a high-output element (electric) or burner (gas) sized to raise the temperature in the few seconds the water is in the unit. That means no standing heat loss between uses, but it also means the unit has to work hard the instant a tap opens, with no buffer to fall back on.

The load shedding problem electric tankless units don’t solve

This is the part that trips up a lot of Alberton homeowners switching from a storage geyser: a storage tank keeps water hot for hours after the power goes off, so load shedding barely registers for hot water. An electric tankless unit has nothing stored — the moment the power cuts, hot water stops immediately, with zero buffer. If load shedding resilience is part of the reason for switching away from an old geyser, an electric tankless unit is a step backward, not forward. Gas tankless units don’t have this problem since they’re not drawing from the grid to heat water, but they come with the same gas-safety and certification requirements as any other gas installation.

Electrical capacity is the real constraint

Electric tankless units need a lot of power in a short burst — often 15-27kW for a single-shower-capable unit, well above the 3-4kW a typical storage geyser element draws. That’s not a “just plug it in” upgrade: it usually means a dedicated circuit, a larger breaker, and sometimes an upgrade to the property’s overall electrical capacity or even the municipal supply agreement, depending on what else is running in the house. Older Alberton properties with older DB boards are the ones most likely to need electrical work done alongside the geyser swap, which changes the cost picture significantly before the geyser itself is even installed.

Multiple bathrooms complicate things

A single tankless unit is generally sized for one point of use at a time, or two if it’s oversized for that purpose. Try to run a shower and a kitchen tap on hot water simultaneously from an undersized unit and the output temperature drops noticeably. Homes with multiple bathrooms in regular concurrent use either need a larger (and more expensive) whole-house unit with the electrical capacity to match, or separate point-of-use units per bathroom — which starts to erode the space and simplicity advantage tankless is supposed to offer.

Upfront cost vs. running cost

The unit itself, plus the electrical work most installations need, usually puts tankless ahead of a like-for-like storage geyser on upfront cost in South Africa. The running-cost argument in its favour is real but modest for an average household — you’re not paying to keep a tank hot overnight, but hot water is a relatively small slice of most homes’ total electricity use compared to what a storage geyser’s standing losses actually cost. It’s worth doing the maths for the specific household rather than assuming the payback period is short by default.

Where tankless genuinely makes sense

• A cottage, flatlet, or granny flat with light, occasional hot water demand
• A point-of-use unit under a single distant bathroom or kitchen sink, rather than replacing the main geyser
• New-build properties where the electrical capacity can be planned in from the start rather than retrofitted
• Gas tankless units specifically, for households already set up for gas and wanting load-shedding-independent hot water without a storage tank

For a typical family home already relying on a storage geyser and regular power cuts, a straight swap to electric tankless usually creates more problems than it solves. It’s worth getting a plumber to actually assess the property’s electrical capacity and hot water usage pattern before committing, rather than deciding on the space savings alone.