A number of water heating systems are available for your household, with some being more energy hungry (and costly) than others.
Electric hot water systems are basically like large kettles. They may be cheap to install, but they can end up costing you a lot of money each year in electricity costs. A typical household with an electric hot water system will use almost a third of its total electricity consumption just for heating the water, costing anywhere up to $600 a year.
Gas storage hot water systems are similarly inefficient in their operation, although they use gas to heat and store the water, rather than electricity. Running costs for a normal sized household can be anywhere up to $1000 a year if there is no reticulated gas supply, which is the case for most Alice Springs suburbs. Gas instantaneous units are more efficient, though these still use fossil fuels and incur annual running costs.
Alice Solar City aims to assist householders in finding more efficient and affordable ways to heat water, and save electricity (or gas) and money in the long term and recommends installing either a solar hot water system or a heat pump water heater.
Solar hot water systems on roofs are a common sight in Alice Springs – about half the homes in Alice Springs homes have already made the switch to solar hot water systems.
Alice Springs has, on average, more sunny days per year than most towns in Australia. Considering water heating accounts for about 29% of the average household energy use, it makes a lot of sense to go solar.
Although it is more expensive to purchase and install a solar hot water system than an electric or gas hot water system, they are more cost effective in the long term.
Solar hot water systems have three main components which are:
The solar collectors - heat from the sun is absorbed through solar collectors;
Hot water storage tank – the heated water is stored in the tank ready for use; and
A booster – used to maintain water temperature during long periods of cloudy or wet weather or when hot water demand is high. Under the Alice Solar City program, installation of a ‘one-shot’ booster control is mandatory (see below for further information).
Solar systems deliver significant savings in water heating costs, depending on how often the booster is used, compared to other hot water systems. In Alice Springs, the running costs for correctly sized and operated solar hot water system for an average family ranges from $50 - $100. This compares to $300-500 for an electric storage system or $500-$1000 for a gas storage system using LPG.
A recent improvement to solar hot water technology is over temperature protection, otherwise known as OTP. Solar hot water systems have a built-in mechanism in to ensure that water in the tank does not over-heat on days of excessive solar radiation. This mechanism involves discharging hot water from the tank when the temperatures approach boiling – a common occurence on a hot summers day in Alice Springs. Whilst this mechanism protects the tank, it also wastes energy and water.
The OTP system prevents over-heating of the water in the tank with the addition of an extra valve and a small over-flow cylinder which is attached to the tank. Once the temperature of the system gets too high the valve will close thereby forcing the heat transfer liquid that runs through the system into the over-flow vessel and preventing the water in the tank from continuing to heat up.
Correct use of the solar hot water booster is critical to ensure low running costs and a longer life for the solar hot water system!
Most systems in Alice Springs use an electric booster, which is generally controlled using a circuit breaker located in the house's switchboard. When the water is colder than desired, the household manually turns on the booster, which heats the tank electrically.
This system relies on householders remembering to turn the booster switch off. Unfortunately, it is common for electric boosters to be left switched on – which means the system uses electricity rather than the sun to heat the water. When this occurs, the system acts exactly like an electric hot water service (consuming a high amount of electricity and costing you significantly more on yur electricity bill.
To address this issue, one-shot boosters are now being used (all systems installed under the Alice Solar City project must utilise a one-shot booster). One-shot boosters are devices that indicate when the booster needs to be used; once the booster is turned on it will heat the water in the tank and then automatically switch off.
Read here for the answers to frequently asked questions about solar hot water.
You can also read more about solar hot water at the following websites.
A heat pump water heater is an alternative to a solar hot water system(SHW) when you want to install a more energy efficient hot water system, but the roof on your home is not suited to installing a solar hot water system or the cost of installation is far too expensive.
A heat pump works like a refrigeration system in reverse. It uses heat from the air (and its own waste heat) to heat the water contained in the tank. Typically, it consumes around one third of the electricity used by an electric water heater to deliver the same amount of hot water. It can even heat water even when the outside temperature drops below zero and when the sun isn't shining, although it is not as energy efficient as a solar hot water heater.
You can read more about Heat pump water heaters at the Living Greener website.
Householders may be eligible to receive a rebate through the Small Scale Technology Certificates (STC's) scheme. which is part of the Australian Government’s Mandatory Renewable Energy Target. The STC's scheme effectively creates a value for the amount of electricity displaced by installing a solar hot water system. Each eligible system generates a set number of STCs, which can be ‘sold’ to organisations who have an obligation to purchase STC's under the Mandatory Renewable Energy Target.
The value of this rebate varies according to the market price for STCs, however, the value of the STC's as at 3 May 2013 is $1,054 for a typical 2 panel 300 litre solar hot water system (ie the 302JOTP) or $782 for a 340 litre domestic heat pump. Householders should check the current STC value applicable for the particular system that they are intending to install, as it can vary considerably and is subject to change.
To take advantage of this STC's rebate, after you have had your system installed, simply complete a short application form, attach relevant documentation and send to the organisation that purchases STC's. Payment is usually made to the householder within a few weeks. In Alice Springs, most householders sell their STC's to Power and Water Corporation – see here for more information.