The two main types of hot water systems are storage and instantaneous systems. These can be powered by electricity, gas and solar electricity. Understanding what options are available can save you money and considering that hot water is used to clean our dishes, the laundry and our bodies, meeting the minimum water temperature is also essential for the health of all occupants.
A healthy hot water
We’ve all been there – standing in the shower fiddling with the taps to find the comfortable water temperature and finding it either too hot or too cold. So at what temperature should water be stored?
Healthhabitat’s Housing for Health – The Guide notes that hot water should be stored at no less than 60°C to prevent growth of harmful organisms; the hot water temperature of the shower, bathtub and hand basin should be tempered to a maximum of 50°C to prevent scalding; and a minimum hot water temperature of 45°C is required at all hot water outlets allowing for temperature loss between the hot water system and the outlets.
Considering that hot water is used to clean our dishes, the laundry and our bodies, meeting the minimum water temperature is essential to the health of all occupants. Make sure that the temperature is not too high as it can then cause severe burns, particularly to children and the elderly.
Understanding hot water systems
The two main types of hot water systems are storage and instantaneous systems. These can be powered by electricity, gas and solar electricity.
Storage hot water systems heat the water and store it in a tank. Hot water is used from the top and replaced by a cold layer at the bottom. The heater at the bottom reheats water when the thermostat detects a drop in temperature. Storage hot water systems are insulated but still lose energy and the water will constantly need to be reheated to reach the set temperature. You may be left with no hot water when the hot water is used faster than the cold water can be heated up.
Instantaneous hot water systems heat water as you go and only the amount required. When you turn on the tap, cold water flows through a heat exchanger. The size of the system you need depends on the number of hot water outlets the system is connected to.
According to Sanctuary magazine, updating your hot water service in your home is one of the best ways to save money on energy bills and lighten your environmental footprint. If you’re looking to purchase a hot water system, speak with your local retailer about which system is right for you and be sure to check the star-rating label.
A special note on solar hot water systems
Solar hot water systems use solar collectors to absorb energy from the sun. Water is heated by the sun as it passes through the collectors. It then flows into an insulated storage tank for later use. There are two main types of solar hot water system corresponding to the two main types of collector: flat plate and evacuated tube. Solar hot water systems should be on the roof in a place that is oriented generally north and not shaded during the day by nearby trees or buildings.
A solar hot water system can supply between 50–95% of your household hot water demand. The percentage depends on where you live; from about 50% in Hobart to around 95% in Darwin. When there is little sun or during the night, the shortfall is typically made up by a back-up electric or gas booster.
Hot water heat pumps are based on the same technology used in refrigerators and reverse cycle air-conditioners and require up to 80% less energy year round than conventional hot water systems. They work by extracting low-grade heat from the air, concentrating it and dumping it into the water in a storage tank. They do not need direct solar energy to operate, although their efficiency is better with higher ambient temperature.
While most solar or heat pump hot water system installations involve the replacement of existing conventional gas or electric water heaters, there are several alternatives to complete system replacement that may cost considerably less but can improve the efficiency of an existing system.
Solar and heat pump hot water systems may qualify for government rebates to reduce the purchase price.
Want more information on efficient hot water systems?
You can also purchase a copy of the Alternative Technology Association’s Efficient Hot Water ebooklet. The ebooklet looks at what to consider before taking the plunge and buying, including type of system, system considerations, sizing, installation, warranties and maintenance.
- CHOICE, <i>Hot water system buying guide</i>
- Healthhabitat, <i>Housing for Health – The Guide</i>
- <i>Sanctuary: Modern Green Homes</i> magazine
- Feature image credit to ©iStock.com/joshblake