Huge Australian government rebates and carbon credits are available for replacing older style storage hot water systems with more efficient ones.
Regional areas get an extra $1000 over metro areas.
The rebates are usually given as a point of sale discount and are in the range of $2500 to $5000 depending on the unit purchased. This amount includes RECs.
The full details of the program can be found at the official home page, Solar Hot Water Rebate Program.