Buy an energy efficient hot water service; gas hot water systems usually carry energy labels. If you chose one which doesn’t have a continuous pilot light, you’ll automatically be saving yourself around $40 a year.
Ensure that your hot water system is appropriate for your needs as well. While it might be tempting to buy a bigger tank because they supply more hot water, larger tanks lose heat quicker and it will drive your bills up constantly re-heating that water. A smaller tank should suffice for a small family.
You can also reduce heat loss from existing electric hot water service units by insulating the tank. If you do wrap insulation around it, be sure you weatherproof the area your hot water service unit is in too.
If you do buy a solar hot water service, ensure you switch the booster off during summer. It will gain enough sun without needing to use the booster.
Australia hot water service units now have Minimum Energy Performance Standards. Any system made after 1999 will lose 30% less heat because of this, so if your unit is old, it may be time for an upgrade, that will pay itself off in a few years time with the money you save on heating the unit.