Just to correct you on a point or two. Hope you do not mind. Extra or idle power is not sent back for the FIT. FIT is paid out on every kilowatt unit that the system generates. When the system is generating power but is not all being used the surplus is sent back to the grid. This is called the Export tariff and not FIT. This is paid out at a far lower rate than the FIT. It is always worked out at 50% of whatever the system generates. this is due to the fact that , unless you have a smart meter, the electricity company cannot afford to put meters in all the homes with solar. Because it is such a nominal amount they are willing to pay out on the basis that you will export 50% of the electricity, whether you use it all or not.
the products you are referring to are power diverters and you are correct, they are a terrific product. We supply them on every install. Even when we give away free solar panels people still want to purchase a diverter to save money on heating water. We make sure that they are set up to divert all surplus energy to go to the immersion instead of back to the grid. They pay for themselves with 2 years and are easily fitted by a competent sparky
