Solar power diverters

These clever little gadgets prevent electricity produced from your solar panels from being exported back to the grid by diverting the electricity to the immersion water heater instead.

Why send excess electricity to your immersion?

The reason for doing this is that under the Feed-in tariff the Government generally assumes you are exporting 50% of what is generated and pay you this accordingly. Therefore, if you can use all the electricity that you produce in your home instead of exporting it then not only do you still benefit from the maximum feed-in tariff payments available you also benefit from the maximum energy savings.

Overall these solar power diverters divert the electricity to the immersion. They monitor the electricity being consumed in the home and the electricity being produced by the solar panels – as soon as there is a surplus being produced they divert this to the immersion unit – without the power diverter in place, this electricity would normally be exported back to the grid – this is where the most common question we get arises.

A common misconception regarding solar power diverters

If the Solar power diverter kicks in at 100 watts surplus PV output, this would not be enough to power the immersion heater, these heaters are rated at 3kW, so would consume at least 3000 watts therefore the extra 2900 watts will be dragged from the grid and electricity bills would be very large.

Excess grid power should be fed to the grid until sufficient power is available to operate the appliances, 70 watts will not do it.


Well obviously, if this was the case it would rather limit the effectiveness of a solar power diverter! Pulling in the shortfall of electricity from the grid would in fact cost you a huge amount of money. Fortunately, they don’t work like that.

The truth about solar power diverters!

A TV and most other appliances that require an electronic power supply can only operate using full mains voltage and the power for which they are rated. If you were to restrict the power flowing into such appliances they will not operate – put simply the TV would not be on!

On the other hand, a heating appliance such as an immersion heater is a pure resistive load and will work at any power regardless of the rated power. In other words, a 3KW immersion element will work quite happily if you were to restrict the power flowing into to say 1.5KW but it would only produce half of its rated heat energy.

Generally, these diverters can electronically regulate the power flowing to such heating devices according to the export power available, just like you can restrict water flow by partially opening a tap.


If the available export power is (say) 100W then the diverter will restrict the power flowing into the immersion to 100W even if the full power rating of the element might be 3000W. This ensures that no grid power is imported to run the immersion.


A system that simply waited until 3KW of export power was available and then turned on the immersion fully would be very inefficient and only be able to save a few percent of the power exported.


A solar power diverter monitors both electricity being consumed by the house and electricity being produced by the solar system and will only divert when there is a surplus of electricity being produced – so hopefully that puts to bed a common misconception of how these clever little units work.