#18338
Sir Humphrey
Strataguru

    …1) The owners seem to be under the impression that they’ll each be getting their own system. That’s 36 inverters and 36 new meters…It would be more efficient for the OC to have one larger system (on the roof that they own) and to use the income to keep levies down. That’s only 1 inverter and 1 new meter.

    Inverters are a small part of the overall cost of a system so there is not actually very much economy of scale from fewer, larger inverters. Indeed it can be more efficient to have multiple inverters. 

    We have 2 inverters in our communal system. If one were to die, half the system would continue to produce power normally while the other is being repaired or replaced. Within each of our inverters are two independent ‘maximum power point trackers’. In effect that means two inverters in each box, so four in all. The benefit of that is that when part of the roof is in shade but part is in full sun, four separate sections can operate independently at the maximum efficiency for their level of illumination. 

    If there were 36 inverters and the panel arranged in 36 groups, each little group could work at maximum efficiency without influence from a fault or different light conditions elsewhere on the roof. 

    Still, 36 does sound a bit excessive. I think it could avoid a lot of potential trouble if there were one system on the roof. That one system might be multiple systems electrically but would look like one unified system. Being on the common property and communally owned all owners would derive the same benefit from that common property, lower levies and a shared warm inner glow etc. 

    …Such things as mould growth, bird poo, wind blown debris and dirty rain can all affect performance. Again, difficult on a 3-storey high pitched roof…

    True, the proposal should include something about how they are to be cleaned. Generally, rain will wash them and cleaning is required relatively infrequently but access for cleaning should be factored in. 

     

    Does your OC have shared electrical costs (say lighting common areas) that would conveniently match or exceed the likely production? If so, it is easier to be confident about the financial return on a net tariff and you could avoid tax issues outlined below.

    Having said all that, If the roof is not being used for anything else, perhaps the OC loses nothing by granting a special privilege to use it to the unit owners that are interested. 

    Another option is solar hot water. Simple, low tech and perhaps it can be hooked up in series with the existing water heaters and consequently need no boosting arrangements.