Best to let it feed back into the grid during the day and get paid for it and then use things during the night to use off peak power. We were getting the PFIT at 66c and only paying about 11c for off peak so used power as little as possible during the day. This is one thing many don't understand about maximising the benefits of solar.
Those benefits have GONE. The high feed-in tariff has gone, at least in NSW, and it's now LESS than the buy cost.
I looked into it about a year ago:
http://somersoft.com/forums/showthread.php?t=73195
... and the feed-in tariff was $0.06 -- less than 1/10 of what you're getting. The numbers just don't work at those rates.