Selecting which type of hot water system is used for a project can often be an afterthought, only considered late in the design process. While for the end user, as with most utilities, cost and convenience will be the great motivators in choosing a system, underestimating the impact the hot water system can have on the sustainability and aesthetics of the finished home can have short and long-term consequences.
Water heating accounts for about 25 per cent of the energy used in the average home and installing the most appropriate and efficient system plays an important role increasing the sustainability of a home while also reducing energy bills.
Selecting a system requires first a decision on the energy source – electricity, gas or solar - and then what type of system, resulting in six main choices: gas storage, gas instant, electric storage, electric heat pump, solar gas boost or solar electric boost.
Here we take a look at the most popular hot water systems’ for detached housing in Australia.
ELECTRIC STORAGE TANKS
As the name would suggest storage tanks heat and then store the water until required for use. Electric storage costs will generally require a lowest capital cost, however the ongoing running costs of these systems are far and away the most expensive. The cost can be reduced using off-peak tariffs to heat the water, but a larger tank is required and can also run the risk running out of hot water. The fact that these systems are also produce the highest levels greenhouse gas emissions and the large amount of space required to accommodate its considerable size can result in a negative impact on a property’s value.
GAS STORAGE
Like its electric counterpart, gas storage tank water is heated and stored in an insulated tank for use when it’s needed and possess the much the same advantages and disadvantages of the electric system. These systems will benefit from gas prices being lower than electricity and as gas rates don’t vary through the day the gas systems can heat water as needed.
ELECTRIC HEAT PUMP
Using heat found in the air outside the unit to heat water, a heat pump uses approximately one third less power than standard electric storage systems. Heat pumps work best in warm humid climates and may not be suitable to cooler climates, but are good option where there is limited space or natural gas is not available.
GAS INSTANT
Instantaneous gas systems heat water only when needed meaning there are none of the heat losses experienced with storage tanks resulting in far greater energy efficiency. While the capital cost is greater a gas instant system will produce far less greenhouse emissions and result in lower energy bills, and will typically have a 5 to 7 Star energy rating.
SOLAR GAS BOOST AND ELECTRIC BOOST
The benefits of solar are well known, with the ability to greatly reduce energy use a solar system provides lower ongoing costs and almost no greenhouse gases. Most systems will require an electric or gas booster to heat the water when sunlight in insufficient, will water heating provided by the solar energy dependent on climate but generally around 90 per cent. The panels, storage tanks and pipes required for the system can present design challenges, initial investment can be high (although government rebates are available in many cases) and the effectiveness of the system can be dependent on location and climate.
When choosing the right system for a project there are a number of variables to be considered including household size, cost, space, available energy sources and the local climate, with each of the above mentioned systems suited differently to these variables.
Once a system has been decided upon, the design and installation of the system must be carefully considered to ensure the efficiency of the system is maximised, energy bills and greenhouse emissions are minimised and most importantly no cold showers.
Here’s some of the best hot water products on the market today:
ELECTRIC STORAGE TANKS
Rheem Australia's RheemPlus range of electric storage heaters range range from 125L for couples and small families through to 315L for large families. RheemPlus provide 5-Star energy efficiency, mains pressure at multiple taps, and a factory fitted tempering valve for fast and easy installation.
ELECTRIC HEAT PUMP
Rinnai Australia Hotflo Split Heat Pump transfers heat found in the air outside the unit to the water stored inside it, and is ideal for situations where a roof-mounted solar system is no practical. Featuring a commercial grade stainless steel tank.
GAS STORAGE
The Australian made Dux Hot Water Prodigy gas storage system offers easy installation with water connections on both sides of the tank. Available in 135 and 170L, its patented world first flue dampner technology delivers 5-star gas efficiency by dramatically reducing heat loss after the heating cycle.
GAS INSTANT
Bosch Hot Water and Heating's Highflow continuous flow gas systems are compact, space-saving and easy to install, and is suitable for homes with up to 3 bathrooms. The range offers 5.5+ energy efficiency star rating and is available in flow rates of 17, 21 and 26 litres per minute. Highflow units can be combined with optional temperature controllers which allow the same temperature shower every time, and also stop hot water flow after a defined volume has been reached allowing residents to run a bathtub and do something else in the meantime.
SOLAR
Solahart Split System Solar Water Heaters are designed for maximum flexibility of installation locations. The low profile and unobtrusive Solahart solar collectors are mounted on a roof facing the equator, whilst the storage tank is mounted at ground level out of sight. The electric boosted model can even be installed inside the home, minimising the visual impact while maximising the potential savings.
