Solar PV Knowledge Bank

Solar PV Optimisers for Hot Water

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Why export when you can divert excess solar electricity?

Solar panels generate the most energy during the day, while most households tend to use most of their electricity in the evening. If there is insufficient load in the house, excess generation from the array will be exported to the grid. This is where an add on like a solar PV optimiser comes in, diverting surplus solar generation into your hot water tank. You may also see these devices referred to as immersion optimisers, power diverters or energy diverters.

Solar PV optimisers monitor electricity export using a sensor attached between your main meter and consumer unit. If the sensor detects that the property is exporting electricity, the device diverts the excess power to the immersion heater in the hot water tank. This reduces the fuel required by the boiler, thereby cutting fuel costs.

If an electrical appliance is switched on in the property, the device will reduce the power diverted to the immersion. Electricity usage throughout the home is always given priority use of the energy generated by the PV array.

The device ensures you make the most of the energy generated by the PV array, even when you are out of the house. As long as your hot water tank has sufficient ‘capacity’ (which can be achieved by setting the normal hot water heating to come on after the sun has gone down) you may be able to use 100% of the electricity generated by your PV system.

The average import cost of electricity is 23.72p/kWh, compared to an average export payment of 15p/kWh. So it makes sense to try to use more solar energy on site, rather than exporting to the grid, particularly if you have electric heating.

The eddi from myenergi

We recommend the eddi from myenergi to provide hot water via excess PV electricity.

Features and benefits:

  • Works with existing immersion elements. You can keep your existing immersion, with no need for expensive replacement work.
  • Integrates well with zappi EV charging (you can choose which device is prioritised).
  • Ability to divert solar into hot water immersion or other types of heating (space, underfloor, pool, towel rail or heat pump).
  • Two heating outputs to divert power sequentially to multiple destinations.
  • LCD screen to monitor power diversion, or pair with the app to set timers.
  • Fanless cooling.
  • Option for wireless installation with myenergi’s harvi.
  • 3 year warranty.

Immersion optimisers vs batteries

Some optimisers like the eddi are compatible with batteries like Tesla Powerwall - they can be installed in such a way to prioritise battery charging, for example. But for most households, a battery should have sufficient capacity to absorb excess solar, leaving little for the immersion optimiser. So we wouldn’t recommend getting both unless your solar solar generation far surpasses your usage.

Other power diverters

There are other devices like the eddi for utilising excess solar power:

  • the Solar iBoost;
  • some inverter manufacturers like Fronius and SolarEdge offer their own power diverters, which can tie in with existing monitoring.

Get in touch today for a power diverter or PV quote:

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