Smart Geyser Controllers: Geyserwise and Others Explained

What a smart geyser controller actually does

A conventional electric geyser has a simple mechanical thermostat. When the water drops below its setting, it switches the element on; when the water reaches it, the element goes off. It does this around the clock, whether anyone needs hot water at 3am or not.

A controller takes over that decision. Depending on the model, it can:

• Show the water temperature from a probe in the tank, so you know how hot the water is before you shower.
• Run timer programmes, so the element only works in the windows you choose.
• Use different temperatures at different times, for example a lower setting during the day and a higher one before the evening rush.
• Control a solar geyser, either the element on a thermosyphon system or the circulation pump on a pumped system.
• Connect to an app over Wi-Fi, so you can check and change settings from your phone.
• Raise alerts for faults such as a failed probe, an empty tank or, on some models, a suspected leak.

How it differs from a simple geyser timer

A timer only switches the power on and off at set times. While the power is on, the geyser's own thermostat still decides when the element runs, and you have no idea what temperature the water is. That is often all you need, and our guide to geyser timer savings and settings covers how to set one up.

A controller adds information and control: a real temperature reading, several setpoints, solar logic and sometimes remote access. You pay more for it, so the question is whether you will use those extras. If you just want the geyser off overnight and during the day, a timer does that job.

The main types you'll find in South Africa

The devices below are described from their manufacturers' and retailers' own pages, checked on 20 October 2026. SolarGuide has no commercial relationship with any of these brands, and we haven't tested them.

Geyserwise electronic thermostats

Geyserwise sells a range of electronic geyser thermostats, and the manufacturer's site lists several models with different jobs:

• Geyserwise TSE1: for normal electric geysers and thermosyphon solar systems. Geyserwise lists a display of water temperature, time, day, heating mode and fault conditions, a daily timer with four time settings, four temperature settings adjustable from 30°C to 75°C, and a mechanical thermal cut-out at 90°C. Its relay is rated at 30A, with a maximum element size of 4kW.
• Geyserwise Delta T: works as a timer on an electric or thermosyphon geyser, or as a differential controller for a 220V pumped solar system, with an anti-freeze setting for the collector.
• Geyserwise Max: for 12V and 220V pumped solar water heating systems. It adds a second probe on the solar collector, so it can run the circulation pump only when the collector is hotter than the tank (Geyserwise gives a default differential of 7°C), plus dry-heat detection for an empty cylinder.
• Tuya module versions: Geyserwise sells TSE1, Delta T and Max models with a Wi-Fi module that works with the Tuya Smart app. The manufacturer says you can view temperatures, set temperatures and switch the geyser on and off from your phone.
• Geyserwise MWS: a different product that heats a geyser element directly from solar panels through a maximum power point tracker (MPPT), without a battery or inverter. More on that below.

The Geyserwise factory default temperature is 55°C, according to the manufacturer. Whether you keep it there is a choice to make with your plumber, which the settings section covers.

Plentify HotBot

HotBot, from the South African company Plentify, is sold as an intelligent controller rather than a thermostat you programme yourself. Plentify says it learns your routine and heats water to suit it, and lists an away mode, a solar mode that uses excess solar energy where available, load-shedding awareness and leak detection. You manage it through the Plentify Home app.

Unlike the others here, it's sold as a subscription. On 20 October 2026 Plentify's HotBot page listed a once-off installation fee of R849 and a monthly subscription of R149, with a two-month free trial and one month's notice to cancel. Plentify lists installation in Gauteng, Durban, Cape Town and selected Western Cape areas. It says HotBot works with electric geysers and thermosyphon solar geysers, but not with gas, heat pump, pumped solar thermal or low-pressure geysers.

Plentify also reports results from a 30-month pilot on 500 electric geysers in Cape Town and the Hessequa municipality, verified by the University of Cape Town. In its write-up, Plentify gives "up to 80%" less energy use per geyser during peak periods and "up to 24%" better water-heating energy efficiency. Those are the provider's reported pilot figures: note the "up to", and treat them as a best case rather than a forecast for your home.

Wi-Fi smart switches

The cheapest "smart" route is a Wi-Fi switch fitted in or near the distribution board on the geyser circuit. One example is Sonoff's POW Elite (POWR320D), which a South African lighting retailer sells as a geyser or pool timer with an energy-monitoring display and app scheduling, listing a maximum load of 3,000W.

A switch like this is really a timer you can control from your phone, with the bonus of showing how many kWh the geyser actually used. It doesn't read the water temperature, so it can't heat to a setpoint or run a solar pump. Check its rating against your element: a 4kW element needs a device, or a contactor, rated for that load. That is a decision for the electrician, not something to guess.

Which settings save money, and which don't

Settings that save money

A sensible temperature. Eskom's hot water fact sheet recommends setting the geyser to 60°C and says you'll save 3% to 5% of water-heating costs for every 10°C reduction. A hotter tank loses heat faster, and you then mix the water back down with cold at the tap. Before going lower than 60°C, talk to your plumber about hygiene settings for stored water.

Heating before you need it, not all day. If the household showers in the morning and evening, there's little point keeping a full tank at temperature through the working day. A controller lets you heat in the hours before each use and let the tank coast in between. The saving comes from part of the standing heat loss, which is smaller than many people expect on a modern, well-insulated geyser. Our geyser cost calculator shows how much of your geyser's daily use is standing loss and how much is the hot water you draw.

An away setting. Eskom advises switching the geyser off when you're away for more than three days and turning it back on three hours before you need hot water. A controller or app makes that easy to do, and to undo remotely on the way home.

Heating from solar. This is the biggest lever. If you have PV panels, a controller or inverter output that heats the water at midday from surplus solar can replace grid electricity with energy you've already paid for. More on that in the next section.

Catching faults. A failed thermostat, a dripping hot tap or a leak can waste energy for weeks. A temperature reading that never settles, or an alert, tells you to call a plumber sooner.

Things that don't save money on their own

• The display. Knowing the temperature is useful, but it doesn't change consumption unless you act on it.
• Switching the geyser off and on all day. The tank still loses heat while it is off, slightly more slowly because the water cools, and the element replaces that heat later. You save part of the standing loss, never the energy to heat the water you use.
• Shifting heating to another hour on a flat tariff. Eskom's Homelight and Homepower tariffs charge the same energy rate at any time of day. Moving the heating window only cuts the cost if you're on a time-of-use tariff, such as Eskom's Homeflex, or if the water is heated from solar.
• Setting the temperature very high "to store more". It increases heat loss and the risk of scalding, and saves nothing.

How controllers work with solar geysers and PV

Solar thermal geysers

A thermosyphon solar geyser has the tank above the collector on the roof and no pump. The controller's only job is the backup element: a timer stops the element heating in the morning before the sun has had a chance. Set it to top up late in the afternoon, only if the sun didn't get the water hot enough.

A pumped solar geyser has the tank inside the roof space and a pump that moves water or fluid through the collectors. It needs a differential controller, which compares collector and tank temperatures and runs the pump when the collector is hotter. Geyserwise's Max and Delta T do this; many pumped systems come with a controller from the supplier. Our guide to solar geysers versus solar PV explains when solar water heating is the better first step.

PV-diverted geysers

If you have solar panels, there are two common ways to heat the geyser from them:

1. Through the inverter. Some hybrid inverters have a programmable auxiliary or "smart load" output that an installer can set to switch the geyser on when the battery is nearly full and the panels are producing more than the house uses. Because a geyser element typically draws 2kW to 4kW, the installer has to make sure it doesn't overload the inverter or drain the battery.2. Directly from dedicated panels. A DC solar geyser controller, such as Geyserwise's MWS, feeds a set of panels straight into a suitable element through an MPPT, with the grid as backup. Geyserwise says its MWS works at up to 99% MPPT efficiency between 120V and 350V DC. Separate panels mean separate roof space.

Either way, a timer or controller on the grid side should leave room for the solar to do the work. If the grid heats the tank to 60°C at 5am, there's nothing left for the panels to do at noon.

If you're weighing a controller against putting the geyser on solar, a PV quote can show how much surplus midday power your roof would produce. Get a solar quote that includes your geyser →

Installation, Certificates of Compliance and warranties

A geyser controller is wired into the geyser circuit, and some models replace the geyser's thermostat with their own probe and relay. That is electrical installation work. The Department of Employment and Labour states that only a registered electrical contractor may issue a Certificate of Compliance (CoC), after inspecting and testing the installation. Ask for one, and keep it with your house papers. Our electrical CoC guide explains what it should cover.

The geyser itself is a separate matter. Kwikot, a geyser manufacturer, says geysers must be installed in line with SANS 10254 by a qualified plumber, and that an insurer may reject a burst-geyser claim if the installation doesn't comply. If a controller install means work on the tank, valves or thermostat pocket, it's worth having the plumber involved too.

Before you buy, check three things:

• The geyser warranty. Ask the geyser manufacturer, in writing, whether replacing the thermostat or adding a probe affects the tank warranty.
• The controller warranty. Find out who handles a claim, and whether the warranty depends on installation by an approved installer.
• Your insurer. Tell them about the change if your policy asks you to, and keep the CoC in case you ever claim for a burst geyser.

Which one suits you?

• You want the geyser off when nobody needs hot water, and nothing more: a timer. Start with our geyser timer guide.
• You want to see the temperature and set different temperatures by time of day: an electronic thermostat-controller such as a Geyserwise TSE1 or Delta T.
• You have a pumped solar geyser: a differential controller is part of the system, so check the one you have before buying another.
• You'd rather not programme anything: a learning controller such as HotBot, if your geyser type and area are covered and the subscription cost makes sense against your hot-water bill.
• You have, or are planning, solar PV: heat the geyser from surplus solar through the inverter or a dedicated DC controller. This changes the energy source, not just the timing, so it's where the big saving is.

If you haven't settled on a geyser type yet, our guide to the types of geysers in South Africa compares electric, gas, solar, heat pump and hybrid units.

Frequently asked questions

What is the best Geyserwise setting to save electricity?

Set the temperature to about 60°C, which Eskom recommends, and programme the timer to heat in the hours before your household uses hot water rather than all day. If you're away for more than three days, switch the geyser off. If you have a solar geyser, let the sun heat the water first and use the element only as a late-afternoon top-up.

Does a smart geyser controller really save money?

It can, but less than the marketing suggests if your geyser is already well insulated and you only change the timing. The real savings come from a lower temperature, avoiding needless reheating, catching faults early and heating from solar instead of the grid. A display or app saves nothing on its own.

Can I install a Geyserwise myself?

You shouldn't. A controller is wired into the geyser circuit and may replace the thermostat. That work needs a registered electrician, who can issue a Certificate of Compliance. DIY work can affect your geyser warranty and an insurance claim.

Will a geyser controller work with my solar panels?

It depends on how the geyser connects to the system. A grid-side controller can be set to leave heating to the solar. To heat the geyser from your panels you need either an inverter output set up to switch on with surplus solar, or a dedicated DC solar geyser controller fed by its own panels. An installer has to size either option.

Is SolarGuide the installer?

No. SolarGuide is an independent referral partner for solar PV. Alumo supplies, installs, finances and warrants the systems, and we help you compare options and get a free quote. We don't sell or install geyser controllers, and pricing for any solar system is indicative and subject to a site assessment and credit approval.

Sources and review note

Checked on 20 October 2026. Geyserwise model features come from the manufacturer's product pages for the TSE1, Delta T, Max, Max with Tuya module and MWS. HotBot features, compatibility, coverage and pricing come from Plentify's HotBot page, and the pilot results from Plentify's report of 8 February 2024; both are provider claims. The Sonoff POW Elite rating comes from a South African retailer's product page. Temperature and away advice is from Eskom's hot water and geyser management fact sheet. Tariff structures are from Eskom's schedule of standard prices for 1 April 2026 to 31 March 2027. CoC requirements are from the Department of Employment and Labour, and geyser compliance and insurance from Kwikot. SolarGuide has not tested these products and has no commercial relationship with their makers. Product names are mentioned for identification only.