PV electricity controller

[ex 2 Base]

We have PV panels on our house roof and would like to use the "export" electricity to feed our immersion heater via a controller, such that it switches on when we are generating.I intend to fit a 1KW immersion heater, so that it dribbles in energy through out the day, using the heater thermostat to control the water temperature.
My question is, has any one any experience or comments of these conrollers or better still a circuit diagram of such a device.

[ppppenguin]

There is, or possibly was, something like this available commerically. Can't find it online at present.

You need to do the sums to see if it's worthwhile. Taking my own PV installation. It's 2kWp and gives about 1600kWh/year. I don't know how much I actually use but let's take the usual 50%. That means there's 800kWh I'm exporting that I could possibly use to heat water. Since I use mains gas for water heating that's perhaps £30/year if I can use all the surplus. On a sunny summer day when I've got most surplus it may well be more than I can use.

If you heat your water with more expensive fuels then the return is better.

[ex 2 Base]

Hello Jeffrey, since posting my request I've had an idea. I connected our 3KW immersion heater via my 110volt site transformer from the PV system. Then I had yet another idea, why generate heat (the transformer got warm) so did a little calculation, and have fitted two 55micro farad capacitors connected in parallel in series with the heater element and thermostat. All works well I'm pleaded to say. Mark 2 version is going to be switchable(variable) via 3 x 20 relays and rotary selector switch. I'll keep you posted Ted