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.
Electric heat pump systems function like a reverse cycle air conditioner. Heat is extracted from the surrounding air, even at quite low ambient temperatures.
Heat pump systems are almost as efficient as solar hot water systems.