This seems to be the problem with all solar and batteries. I started another thread about this, the FIT (closed to new applicants on March 31, 2019) you were guaranteed a payment, so you could say in X years it will have paid for its self. The Smart Export Guarantee (SEG) replaced it, and it seems the payment is anything but guaranteed.
It seems the organisations Flexi-Orb and the like are not required to get the second MPAN number, but it is difficult to get it all sorted with the Flexi-Orb never mind without it.
The Octopus offer does make it easier, but is simply should not be required, but for first 20 months with British Gas, even with the Flexi-Orb number, I got no payment for export, so 2024 I exported 2625.7 kWh and 2025 it was 3054.7 and to date 2026 it is 2969.3 kWh, so average is around the 2900 kWh per year. At 15p/kWh 20 months is around £725 that British Gas swindled me out of.
OK, plug in will not produce as much, I have 6 kW of panels with 5 kW inverter, and 6.4 kWh of storage. But all which is guaranteed, it what I use myself, so at around 25p/kWh and the production - export. Since fitted approx 3 years used in house 9523.2 kWh so £2380.80 solar used at 25p/kWh.
This is a fraction of what has really been saved, as charging batteries overnight at cheap rate, and using during the day, plus the export so add another £1000 for electricity exported, and £600 for the off-peak used during peak hours, so for 3 years around £4000 saved. But of that £4000 only £2300 is due to solar directly.
When I consider running washing machine, tumble drier, and dishwasher at night the sum saved increases, but also a loss converting much more realistic is more like £3500. But I can say over £1000 a year saved, but just the panels, £750 saved.
