My father in law just had in April a 28% discount on usage charges (not daily charges though) account set up by my brother in law with another company. Previously he had been on a 2% pay on time reduction from AGL. So I checked this 28% discount out.
AGL Peak usage charge $0.26/kwh, Controlled supply $0.22/kwh Daily service charge Peak $1.00/day Controlled $0.03/day This lead to a total bill of about $243 per quarter (out by a few cents) all before the 2% discount and after his pensioner discount.
The other company (in same order) $0.324, $0.28, $1.309, $0.03 which based on the figure from AGL usage and after 28% discount on usage charges and pensioner discount was $258 for the same quarter.
AGL in the meantime has responded with a 30% discount on usage charges which means his old $0.26 peak drops to about $0.189 and a correspondingly cheaper controlled supply charge. Using the same figures as before will put his bill at $179.
So not every discount can really save you money and may make you worse off. My father in law is now happily back with AGL and enjoying a much better deal.