The technology available in the solar collector, from flat plate to evacuated tube, is also becoming increasingly popular. Flat plate offers many different options in their characteristics. Many collectors in the Australian market offer a choice of aluminium or all copper absorber, while the selective surface applied to that absorber can have a dramatic effect on the efficiency of the system from the basic black paint right up to the highly efficient TiNOX.

Black selective surfaces are very good absorbers of solar radiation, however the disadvantage is the hot absorber surface starts to emit energy as infrared radiation, thus about 50 per cent of the absorbed energy will be lost before it can be transferred to the liquid.

TiNOX on the other hand uses solar radiation energy and is irradiated in a different wave-length range, as heat radiation of a hot surface, thus enabling TiNOX to convert up to 90 per cent of the solar radiation into heat.

The option of evacuated tube over flat plate collectors provides another alternative.

Although it is heralded that the evacuated tube is a more efficient collector than the flat plate, this perception is rarely backed by scientific data or independent test results.

Tests carried out on more than 160 different solar panels by the research organisation Solartechnik Prufung Forschung found that the average gross efficiency of flat plate collectors was approximately 70 per cent, considerably higher than evacuated tube collectors, which averaged 49 per cent.

Solar hot water systems are predominantly available in two configurations: thermosyphon and split systems. Read more about these two alternatives on page 86.

Heat pumps have experienced a surge in the Australian market over the last 2–3 years due to state regulations restricting the replacement of the standard electric storage tank.

A heat pump works by drawing heat out of the outside air and converting it to the liquid in the tank via a heat exchange system. Heat pumps are required to be connected to peak electricity, which can add up to 100–200percent to the cost of every kilowatt being used in heating water as opposed to an electric storage tank on off-peak rates. While you are using up to 60per cent less energy to heat your water, you may be paying as much as 200 per cent per kilowatt, and you will not save any money compared to using a standard electric storage tank.

There are many claims that heat pumps are better than solar hot water systems, and this can be the case in areas where the ambient air temperature and humidity is consistently high, such as the Northern Territory and northern Queensland. But it is not so much the case in the mid and southern states where there have been many cases where the consumers have actually reported an increase in their electricity bills.

In most cases heat pumps are easier to install than solar; your typical one-man plumber can complete the installation. Unfortunately in the solar hot water industry there seems to be a lack of factual information for the consumer and the plumber. Information can provide the consumer or plumber with the knowledge to make an informed decision, but unfortunately the solar hot water industry has too many people looking for the quick sales – and not always providing the correct solution to suit the application.

The Australian hot water market consists of over 750,000 installations in breakdown/replacement and new homes per annum, and while solar hot water makes up only 8–10 per cent of that number, solar hot water installations have only grown by 3-4 per cent over the last five years. States such as South Australia and Queensland have moved to ban the installation of electric storage tanks in the replacement market, thus stimulating growth in the solar market, but unless the other states adopt the same strategy or the federal government pushes for national legislation in the reduction of electric tanks, the solar hot water industry will continue to experience slow growth.