Reimagine Hot Water

It’s the only solution that retrofits standard electric geysers and is solar PV-ready—combining smart thermostat control, connected monitoring and seamless solar integration.

Yes — if you have a compatible geyser (for example from your preferred brand), your electrician can replace the thermostat with the Elon smart unit and convert it into a smart, solar-ready heater.

The Elon 100 is a solar-PV water-heater kit. The Smart Water solution is a next-generation smart thermostat with solar-PV capability. Both allow you to connect solar PV modules to your standard electric geyser, but the Elon Smart has additional benefits and capabilities, including being able to see the water temperature, monitor and control your geyser from a smartphone.

The most important factor here is the total size or power of the solar PV array (measured in kilowatt or kWp) rather than the number of modules. We recommend a minimum of 1 kWp. The maximum solar power rating for the Elon 100 is 4 kWp and for the Elon Smart it is 3 kWp. DO NOT exceed the maximum solar voltage and current ratings for the Elon 100 and Elon Smart, which are as follows: Elon 100: Isc < 20A DC, Voc < 250V DC. Elon Smart: Isc < 15A DC, Voc < 230V DC. The size of solar PV array required depends on the number of people in the household as well as your hot water usage levels. Please note: two parallel strings are only allowed for Elon 100, and only where the short-circuit current (Isc) of the panels are less than 10A (so that the short-circuit current of the parallel string would be less than 20A).

Loadshedding: Both the Elon 100 and Elon Smart will continue functioning during loadshedding as long as the sun is shining. If there is loadshedding at night or when there is no sun, then the Elon 100 or Elon Smart will be off. Power surges: The Elon 100 has AC overvoltage protection and can withstand AC voltages of up to 500V (more than double the normal 230V AC voltage) indefinitely. At voltages above 270V, it will disconnect the element to protect it. Once the voltage returns to the ‘normal’ range, it will reconnect the element. The Elon Smart also has extensive surge protection built in. However, for high lightning strike areas, installation of a surge protection device (SPD) is recommended.

Off-grid. The Elon 100 and the Elon Smart both have a double-pole, double-throw, break-before-make changeover relay that switches power supply to the element between solar PV (DC) and grid (AC). That means that it is mechanically impossible for DC power to flow into the AC supply or for AC power to flow into the DC supply. Hence, the Elon qualifies as ‘off-grid’ for solar PV installations.

No, the Elon Smart is designed to fit into Kwikot geysers. It should NOT be installed in geysers from other manufacturers.

No, at this time the Elon Smart is NOT compatible with Xtend PTC elements.

No, neither the Elon 100 nor the Elon Smart have a MPPT. Maximum Power Point Tracking (MPPT) is a technique used with variable power sources like solar PV modules to maximise energy extraction as the power output varies. Most inverters and charge controllers have MPPT built in. However, MPPT adds cost, and is not strictly necessary where direct DC energy is utilised. If the solar PV string and geyser element are matched well, the energy loss for a system with no MPPT vs a system with MPPT is small. In fact, for Elon units, the loss is less than 10% when the PV string and element are matched well. This is because both the Elon 100 and Elon Smart start feeding energy to the geyser at just 20V under load, whilst most MPPT systems require 100 to 150V to become operational. Hence, in low light and cloudy conditions, the Elon feeds energy to the geyser at times when an inverter or MPPT would not switch on at all. This makes up at least partially for the loss in efficiency due to the lack of a MPPT. It’s more cost-effective to add a solar PV module than to add a MPPT.

Yes, you can connect your inverter AC output to the Elon Smart AC (grid) input. However, you should remember that, when the element is drawing power from the AC side via the Elon Smart, it will draw the full power rating of the element. For example, if it is a 3 kW element, it will draw 3 kW of power. If it is a 4 kW element, it will draw 4 kW of power. Thus, you will need at least an 8 kW inverter to avoid frequent inverter tripping. Even for an 8 kW inverter, you cannot switch on many high-powered appliances at the same time as the geyser. You should also keep in mind that a 3 or 4 kW power draw can drain your batteries quickly. Hence, you only want to use inverter geyser heating in the early to mid-afternoon, when batteries are typically fully charged and the solar PV output is high. The recommended time zone for custom AC heating timer settings on the Elon Smart is in the 12:30 to 15:00 window. You can experiment with the length of this ‘boost’ window to suit your specific circumstances and solar PV installation (for example, you can set it to run on AC / grid power from 13:30 to 15:00). An alternative is to manually press the ‘heat with grid now’ button in the Elon Smart app on days when the batteries are full. But this requires manual monitoring, which is not always desirable. Please note: Do NOT install a timer between the inverter and the Elon Smart. The inverter should be set up to always supply power to the Elon Smart. Use the Elon Smart’s custom timers to control when the geyser is heated from the inverter.

kWh is a unit of energy. It is equivalent to 1 kilowatt (kW) of power expended for 1 hour. If you have a light bulb of 100W, then it will consume 1 kWh in 10 hours (0.1 kW x 10h = 1 kWh). If you have a geyser with a 3 kW element, then it will consume 3 kWh every hour when using grid power.

Explore the website (see for example the Projects page and the Resources page) or contact the PowerOptimal team for more information.