Choosing a Hot Water System
Hot water accounts for up to 40% of a household's energy costs, so it's important to think carefully before selecting your hot water system.
Choosing the most appropriate system for your needs, together with the wise use of your system, can considerably lower your hot water costs.
By purchasing an energy efficient solar, heat pump or natural gas water heater you will be reducing your water heating bill and greenhouse pollution from your water heater by up to 70%.
Decision 1 – Storage or continuous flow (instantaneous) water heaters?
Both types are suitable for most households. However, your decision should be based on the size of your household, purchase and installation price, the unit's efficiency and running costs, and life expectancy of the unit.
Storage water heaters
Continuous flow (instantaneous) water heaters
- Water is heated and stored in an insulated tank ready for use throughout the day
- Operate most economically on solar energy, natural gas or off-peak electricity. They can also run on LPG, peak electricity or solid fuels such as wood.
Decision 2 – Electric, gas or solar?
- Heat water as it is required, and therefore don't require a storage tank. As water is heated instantaneously, they cannot run out of hot water.
- Operate most economically on natural gas, but can also use LPG and general tariff electricity.
- Can be used for storage and continuous flow systems
- Systems are rated for their energy efficiency with energy rating labels – the more stars, the more energy efficient.
- Internal and external models available.
- Storage water heaters have smaller capacities than off-peak electric systems, as water can be reheated at any time of the day or night.
- Running costs similar to natural gas.
- Only available for use in storage systems of 160 litres capacity or greater.
- Water is heated overnight to provide adequate hot water for daily usage.
- Twin element units can operate with a 24-hour off-peak boost. If hot water runs out, water is reheated automatically on the off-peak tariff. To qualify for off-peak reheat, units must be sized according to the number of potential bedrooms in the home. Check with your electricity supplier for more information.
- Not available for continuous flow systems.
- Internal and external models available.
- In NSW, a solar hot water heater will provide approximately 65-80% of your hot water free of charge, and is very beneficial to the environment.
- Generally the cheapest systems to run
- For an additional investment of $1500-$2000 above the price of a conventional hot water system, a solar system can pay for itself in approximately 5-10 years, depending on your household's water consumption
- Bear in mind that solar systems have long life expectancies than most conventional systems, which further reduces their overall pay-back period. A shorter pay-back period can also be expected in areas with higher levels of solar radiation, eg western NSW
- All systems come with a gas, off-peak electric or solid fuel booster to supply adequate hot water during periods of low sunshine
- Solar panels are located on the roof, with a storage tank either located on the roof or at ground level.
- Mains pressure and constant pressure systems available
Solid fuels (wood, briquettes, coal etc)
- Used in areas where natural gas is not available
- Running costs average around one and a half to two times the price of natural gas or off-peak electricity
- Look for the energy rating label with the highest number of stars
- Suitable for storage and continuous flow units
- Cost of fuels vary greatly
- Can be used alone, or in conjunction with off-peak electricity and/or solar in constant pressue storage units
- Water can be heated using a 'wetback' attached to a slow combustion wood heater, or a stand-alone water heater powered by solid fuel
- Must not be used with mains pressure systems, unless a heat exchanger is used
- Not available for continuous flow systems
- Used for electric continuous flow units, storage water heaters with a capacity of less than 160 litres and heat pump type storage systems
- Can be very expensive to run so should only be used with other options are not possible
- Common in flats, units etc where space is limited
- High efficiency form of water heating which use around 70% less electricity than other electric water heaters
- Heat is extracted from the atmosphere using a refrigerant gas and a compressor (much the same way as heat is extracted from your refrigerator) and used to heat water stored in a tank at ground levels
- Have lower running costs than normal 'peak rate' electric storage units because of their high efficiency and when used in conjunction with a timer and the off-peak tariff, running costs are even lower
Decision 3 – What Size?
Note: High water usage households (e.g. those with spas or dishwashers) should select the next largest system size in the range. A dishwasher with a hot water connection should be counted as an extra person.