Hot-water production is the generally the second highest energy consumer for residential facilities. (Behind HVAC) The number one priority to reduce energy use in hot-water production is to replace electric storage hot-water systems. If you upgrade to a gas-boosted solar system, annual operating costs can drop by as much as 90 per cent.
OPTION 1 – Solar hot water
Solar water heating is the most energy-efficient means of heating water. Supplementary heating is typically required to boost water to the required temperature (e.g. on cloudy days or at night). Gas boosting should be used in preference to electric boosting where this is available.
OPTION 2 – Gas hot water
In instances where solar hot-water heating is not possible because of roof constraints, gas hot-water heating systems are recommended.
OPTION 3 – Air-source heat pump
In instances where solar or gas hot-water systems are not possible, then an air-source heat pump is recommended. These are still three times more efficient than an electric storage system as they only use electricity to pump refrigerant around the system, not to heat the water. In alpine areas, heat pump systems are not practical and ground-source heat pumps should be considered.
It should be stated that no matter what form of water heating is used, reducing your use of hot water will also reduce your energy use.
The following ‘physical’ options should be explored when looking to reduce water usage:
Investigate whether you have water-efficient devices in bathrooms and kitchens
Minimising the amount of hot water used also reduces the energy required to heat the water. Install water saving devices in both kitchens and bathrooms, for example tap aerators or flow restrictors, water efficient pre-rinse nozzles and water efficient showerheads.
Check your hot-water distribution system. Insulating this pipework can reduce heat losses by up to 70 per cent. Heat loss reductions will also enable you to lower the outlet temperature of hot-water systems. Running hot-water systems at higher than necessary temperatures to reduce the risk of legionella will also increase your energy requirements. A minimum temperature of 60°C must be maintained to prevent legionella in a hot-water storage system.
The following ‘behaviour focused’ options should be explored in conjunction with physical options:
- work on behaviour management through educating occupants as to usage issues and costs
- demonstrate trends through energy and water usage data
- set targets with stakeholder involvement in reductions and measure and report of progress at regular intervals