It depends on the situation. For example, a family with 4 members and 4 kW solar PV system can expect a saving of about £200 per year after installing SolarImmersion.
Yes, installing SolarImmersion will not affect your export or production FIT payouts.
ROI period of SolarImmersion depends on several factors. However, on average you could expect a payback period of 1-2 years.
This really depends on the surplus power available and how much water is being used. On average, the water will hit 60C before midday on sunny days and by mid afternoon when it’s cloudy.