Hi Clive

The iBoost works by sending unused power to the immersion heater which would normally be exported.
If your solar pv system is generating 2 kw of power and your house is only using 1 kw of power at that time, the iBoost or Immersun unit will send 1 kw to the immersion heater. You don’t need over 3 kw to be generated for the device to work.