The system we install, the Eddi, is intelligent. So, only excess solar power is used to heat your water tank. The Eddi works by continuously measuring your solar generation and your household consumption and then diverting any excess energy to your hot water immersion heater.
The system will adjust the flow of energy to your immersion heater in response to changes in your solar generation and your consumption, as you go about your daily life.
For example, on a sunny day the device may divert a full 3kW to your immersion heater. If the day becomes cloudy the device will adjust the energy being diverted as the output of your solar PV system drops.
This is a particularly efficient use of energy because immersion heating uses what’s called a resistive element. This basically means that however much energy is available at any time that energy can still be diverted and used, as an immersion heater does not require a certain amount of energy to be “on”. You can compare this to a kettle which requires a set amount of energy to switch on and anything less than that is ineffective.