Water heating with solar energy

The Solar Association has a number of members who are focused on meeting the customers needs – hot water, and supply both SWH and HPWH systems. Suppliers often offer SWH and HPWH systems as they are seen as being complementary and the potential customer can be offered the best hot water supply solution appropriate to their situation. Customers generally don’t want to buy a particular technology, eg SWH or HPWH per se, they want the best hot water solution for their needs.

Solar Water Heaters

Typically, approximately a third of the energy consumed by the home is used to heat water. Where the lighting and appliances are of energy efficient types, this can increase to 50%. Water heating represents the single largest opportunity to decrease household energy bills in most homes. Solar water heating is a form of renewable energy which will substantially reduce water heating bills. Solar water heaters have few moving parts, are highly effective at converting solar radiation into usable hot water and have proven durability.

Heat Pump Water Heating

Heat pump water heaters offer an alternative approach to heat water, in which electricity is used to drive a refrigeration cycle. They can be considered an indirect solar energy sourced water heater. The heat pump cycle extracts heat from the air using a refrigerant, then concentrates the heat energy, and transfers it into the water. The electrical energy used in this process is significantly less than that used by an electrical resistance heater in a conventional water heater, and therefore a heat-pump water heater is an energy efficient device.

Internationally technical standards for SWH and HPWH are often combined as many aspects of each technology are common. This also occurs in New Zealand where the standards AS/NZS 2712:2007 and AS/NZS 4234:2008 both cover SWH and HPWH.

For further information on HPWH click here.

Gas Water Heating

In many areas of New Zealand there is an option for heating water by use of gas. Bottled LPG is an expensive option to heat water, with the cost being being very similar to that of electricity. Reticulated gas is significantly cheaper per unit of gas, however the supply charge results in this option only cheaper than electricity when the consumption is high. Heating water using gas also results in very high greenhouse gas emissions compared with electricity. Gas is however, an excellent choice as a supplementary heater for a solar water heating system. Solar is the primary heating system with the continuous gas heater boosting the temperature of the water if the solar has not heated it adequately for use. This results in lower greenhouse gas emissions than using gas to generate electricity, and then using that electricity to heat the water.

Wood Pellet Heaters/Boilers

Installing a wood pellet heater with a wet back or a wood pellet boiler as supplementary heating to a solar system provides year round supply of hot water for renewable energy sources.

Examples of Solar Water Heating Installations

There are a wide number of typical situations where solar water heating is being installed. Examples are shown on the attached reference sheets.

Solar Water Heating Reference Installations attachment here (note name change from SIA).

The Future

All members of the Association are expected to meet the Association's Code of Conduct. For a copy of the Code of Conduct click here (pdf 26kb).