Conventional electric geyser
This is the storage cylinder found in most homes: an insulated tank of 100 to 250 litres with an electric element and a thermostat. It heats the whole tank to a set temperature and holds it there, reheating whenever hot water is drawn or heat is lost through the tank walls.
It is the cheapest type to buy and the simplest to install, and every plumber knows it. It is also the most expensive to run, because every unit of heat comes from an electric element at full grid tariff, and because it keeps a large volume of water hot around the clock whether you use it or not. A timer or a smart geyser controller that heats only before the morning and evening peaks is the cheapest improvement most households can make, and our guide to reducing your Eskom bill explains how much of the bill it touches.
During load-shedding a conventional geyser cannot heat, but a full, well-insulated tank keeps water hot for hours, so a two-hour outage rarely means a cold shower. A geyser element is too large a load for most home batteries, which is why solar PV installers usually leave it off the backed-up circuits.
Gas geyser
A gas geyser heats water only as it flows through the unit, using LPG from a cylinder. There is no storage tank, so there is no standing heat loss and no waiting for a tank to recover. Hot water lasts as long as the gas does, which also makes gas the most load-shedding-proof option of all: it does not need electricity at all, apart from a small battery or mains connection for ignition on some models.
The trade-offs are the cost and logistics of gas refills, a flow rate that can struggle with two showers at once, the need for proper ventilation and a certified installer, and the fact that gas pricing moves independently of electricity. Gas suits smaller households, holiday homes and anyone who wants hot water to be entirely independent of the grid. Our gas vs solar vs battery guide looks at where gas fits alongside a solar system.
Solar geyser
A solar geyser collects heat from the sun, either through flat-plate collectors or evacuated tubes on the roof, and stores the hot water in a tank. Some systems mount the tank on the roof above the collector and rely on natural circulation; others keep the tank inside or in the ceiling and use a small pump. Almost all include an electric backup element for cloudy spells and winter.
On a sunny South African roof a solar geyser can cover most of a household's hot water for much of the year, which makes it one of the biggest single savings available on an electricity bill. The important limits are that it needs an unshaded, structurally sound roof, that it still draws grid power for the backup element, and that it does nothing for the rest of the home during load-shedding. Our solar geyser vs solar PV comparison explains when to start with water heating and when to start with panels.
Heat pump geyser
A heat pump does not collect sunlight. It uses a small compressor, like a fridge running in reverse, to move heat from the surrounding air into the water in the tank. Because it moves heat rather than generating it, it uses far less electricity than an element for the same job, and it works at night and on overcast days.
Heat pumps are often the practical choice where a roof is shaded or unsuitable for collectors, where the home already has a good cylinder that can be retrofitted, or where the household plans a solar PV system and wants a water heater that can be scheduled to run off the panels during the day. They have their own installation, noise and maintenance considerations, and they still need grid or battery power to run, so they do not help with load-shedding on their own.
Hybrid electric-solar geyser
A hybrid is a conventional-looking electric cylinder designed to accept heat from a solar collector or a small dedicated PV array as well as from its element. Some units run the element directly from a few solar panels through a controller, so daytime sun heats the water without a separate collector or a battery, and the grid tops up when needed.
Hybrids are attractive for homes that want a solar contribution to water heating with minimal roof plumbing, or that are adding a modest PV array anyway. The savings depend heavily on how the controller prioritises solar over grid, so ask for the control logic in plain language before you buy. Like the other electric types, a hybrid cannot heat during an outage unless it is fed from a battery-backed system.
How to choose the right type
Start with your roof and your hot-water pattern
An unshaded north-facing roof with sound structure favours a solar geyser. A shaded or crowded roof favours a heat pump. A small household that showers in the evening has different needs from a family of five with a morning rush, and the tank size matters as much as the technology; our solar geyser prices guide explains what 100L, 150L and 200L labels actually mean.
Decide what load-shedding means to you
If uninterrupted hot water during outages is the goal, gas is the simplest answer and a full solar geyser tank is a close second. If the goal is keeping the whole home running, the answer is solar PV with a battery, and the geyser type becomes a secondary decision that a good PV design accounts for. Our guide to what a 5kWh battery can run shows why a geyser element rarely belongs on the backup circuit.
Think about the geyser and solar PV together
Water heating and solar PV interact. A heat pump or a scheduled electric geyser can soak up midday solar production that would otherwise be exported or wasted, while a solar geyser reduces the electrical load a PV system has to cover. If you are planning panels, tell the installer how you heat water before the system is sized. SolarGuide can arrange a free, no-obligation solar PV quote through Alumo; confirm the geyser or heat-pump product and installation scope with its supplier.
Frequently asked questions
What is the cheapest type of geyser to run in South Africa?
A solar geyser on a good roof or a heat pump generally has the lowest running cost, because most of the heat comes from the sun or from the air rather than from a grid-powered element. A conventional electric geyser is the cheapest to buy and the most expensive to run.
Which geyser works during load-shedding?
A gas geyser with battery ignition can work without the grid; models with mains-powered controls or pumps may not. Any insulated tank can keep supplying the hot water already stored. A passive solar-thermal system may continue collecting heat, while pumped systems and electric backup elements need power. A battery-backed PV system can heat an electric geyser during an outage only when the inverter and battery were sized and wired for that load.
Is a heat pump a type of solar geyser?
No. A heat pump uses electricity efficiently to move heat from the air into the water; it does not collect sunlight. It is often compared with solar geysers because both cut the water-heating bill, but they suit different roofs and homes.
Can I keep my existing geyser and still save?
Often, yes. A timer or smart controller reduces a conventional geyser's running cost, a heat pump can be retrofitted to a suitable existing cylinder, and a hybrid conversion can add a solar contribution without replacing the tank.
Does SolarGuide install geysers?
No. SolarGuide is an independent referral partner for solar PV systems, which Alumo supplies, installs, finances and warrants. For geysers and heat pumps we publish buying guidance only, so ask your chosen supplier for a written quote that lists the tank size, collector or unit type, backup arrangement and warranty.
Product availability, pricing, installation requirements and warranty terms should be confirmed with a qualified supplier before you buy.
