8 Feb '11: I enquired of EvoEnergy today about adding additional PV to my roof. My motivation is to make the house Carbon Zero, not to maximise the Feed in tariff - so I want to generate more electricity!
Another system is really impractical. To work in the FIT system it would need another inverter and grid connection - as this would have to be on the West facing roof, it is not worth it, because that is tilted to the north, and shaded by a dormer at the south end of the west roof.
If I added a couple more panels to the existing roof, it would push it to 4.32 kW, and the Inverter is probably rated only for 4 kW - although it faces east, there is a possibility of the roof exceeding 4 kW on early midsummer mornings. With the feed in tariff reducing to 36.1 pence/kWh, there would be a drop in income, but this is not a problem for me as I primarily want to go for a higher annual total.
However, the Sunny Boy Inverter would seem to define the limits of expansion.
I have my spare PV panel which my wife would like me to remove from the conservatory. I am tempted to fit it to the south wall, for battery charging, which could power some of the night time functions in the house. I already have a regulator and a 600W inverter for this purpose. If it doesn't make enough power, the PV panel could be replaced with a new, higher output one.