About the ROCs, I intend to produce 1700kWh a year, how many rocs will I get ? If I get only one, is the next 700 moved to the second year? Can I declare less and then declare 2000kWh?
You'd two 2 ROCs for annual output in the range 1500-2499kWh. So that's OK then for the typical output from a 2-ish kWp system. That's 'old' ROCs - not yet sure what happens with the double-ROCs-for-PV from 2009 i.e. do you get 4 for 1500-2499kWh, or you still get 2 but they are special 'double' ones, or is it one per 500kWh. My guess if the first of those 3 options.
I'd have to disagree slightly with that as "it depends".
If you have appointed your energy supplier as your ROC agent then the usual situation is that they will amalgamate all of the kWh generated by their customers and the 500 rounding-up applies on the total figure. They will then pay you the exact amount of ROCs based on your generation figure - so for Stef's 1700 kWh they would pay for 1.7 ROCs.
If you are using a separate ROC agent then their own contract conditions will apply but I would expect the same amalgamation and exact payment would be the norm although I haven't checked into it.
If you are handling ROCs yourself then the rounding up from each 500 units will apply.
That's my understanding anyway.
I haven't seen anything in writing showing how the double ROCs will be handled yet.