Hot water can be very expensive if not installed correctly. Something that I notice a lot when I go to a domestic residence that has just had the electric water heater replaced, is that the customer is paying too much to heat the system. There are several ways that you can make small changes to save a lot of money.
If you do your homework and get some informed advice before you purchase or replace your new hot water system, the energy saving can be quite significant. Considering that your hot water unit is one of the big energy users in your household, taking the time to choose the best hot water system for you makes a lot of sense.
Lets talk about a situation with a standard house hold accommodating 2 adults and a couple of children.
Scenario 1.
If you have no PV Panels on the roof, you should consider purchasing a larger unit such as a 315 Litre system and connect it to a night rate tariff. Although the initial cost of a larger system is more, you will more than recovery that cost in the electricity savings over the life of the unit. If you have PV (Photo Voltaic) panels and are on a high feed in tariff, you should also consider this arrangement.
Scenario 2.
If you have PV panels and are only receiving a small feed in tariff, consider this option. Purchase a system with at least 250 Litre  capacity with a low wattage element such as 1.8 or 2.4kw. As you optimally need to run your hot water system during the hours that the PV panels are producing power, consider fitting a time clock to the circuit. By using a low wattage element, you minimise the risk of the hot water system using more power than the PV panels can produce.This system works very well when the house is generally unoccupied during the day, such as kids at school and the parents at work. There is no point in feeding electricity into the grid at a low rate when you can be heating your hot water for free.
Note: If your household showers morning and night, you may need to consider a larger capacity electric water heater.
