Correctly matching the size of a storage water heater to your hot water needs is essential for greatest efficiency. Storage water heaters operate most economically on solar energy, natural gas and off-peak electricity. They can also be run on LPG, day rate electricity or solid fuels such as wood and briquettes. Instantaneous heaters operate most economically on natural gas but can also use LPG and day rate electricity. Electric units can be fitted under a sink or in a small cupboard.
Water is delivered at near mains pressure or reduced pressure.
Standard units can generally deliver adequate hot water to one or two points at the one time. New high power, high efficiency gas units are able to deliver hot water at a constant temperature to several points around the home at one time, making these systems also suitable for larger households. Instantaneous systems are sized according to the required flow rate. As always, consult the suppliers or manufacturers for specific sizing guidelines for their products. The more stars on the label, the more energy efficient the water heater and lower the running costs.