We have just installed in our home an electronic device called the Intelligent Immersion I2. This small piece of kit diverts any PV energy which would have been exported to the grid into our immersion tank, thereby creating hot water. We have been surprised by the efficiency of the device because even during the short December days, on a sunny day we have been getting piping hot water from our immersion.

The kit comes with a little sensor which clamps on the mains supply in our consumer unit. The sensor measures the flow of electricity to and from the national grid. When the sensor notices that electricity is about to be exported, the I2 device diverts any such electricity to our immersion heater circuit. Therefore our hot water tank will heat up when the sun shines. When the hot water is up to temperature, the immersion's internal thermostat cuts out to prevent over-heating. As we usually heat our hot water with our oil central heating, we anticipate using less oil in future.

The kit which costs about £250 took our electrician less than an hour to install. The unit is manufactured in the UK and I've found the manufacturer to be very helpful, answering all my questions. You can find out more at the Intelligent Immersion website.