Woops, arithmetic mistake.

With a standard 5kWh/day consumption, the 2kWh bought from the grid in winter (at conventional rates) would cost some $33, and the 3kWh/day exported in summer would earn $50, leaving $17 profit annually. In usefulness, the net feed-in tariff is strictly for larger installations of 3kW and up.

should read instead,

With a standard 5kWh/day consumption, the 2kWh bought from the grid in winter (at conventional rates) would cost some $33, and the 3kWh/day exported in summer would earn $162, leaving $129 profit annually, which is not nothing, but not huge, and that level of export is easily wiped out by some airconditioning use. In usefulness, the net feed-in tariff is really for larger installations of 3kW and up.

Maybe Gav will be nice and edit the bolded portion for me ;)