just saw in the news a week or so ago, probably in Today Tonight, that the reason utilities company are giving way bigger discount were because they actually overcharged customer in the last two years, or similar kind of reason. This apparently related to carbon tax, etc. So they have been asked to "refund" the money. I think now instead of refunding, they try to give bigger discount as to retain the customers, and also to show that they care about them, which in truth is a little bit of b*** sh***.
I got a letter from AGL to increase my previous discount of 5 percent to 14 and 16 percent respectively for gas and electricity. As I am very lazy to to anything, I just stay with them.