So if you do an iboost makes a lot of sense, diverts any excess above 100 watts which isn't being used by the house or to charge the batteries straight to your immersion. Ive had one installed now since Feb last year and since then it’s given the immersion 1254 kw of free electricity. Summer months i get about 6kw a day which equates to 2 full hours of power. I dont waste a watt of solar now as if it doesn't get used by the house or the immersion i get the octopus export tariff.