Water and water heater

A four-person family uses around 3500 - 6500 kWh of energy annually for the domestic hot water.

So the variation is wide and you have great opportunities for influencing the energy consumption by making your lifestyle habits and equipment more efficient.

Water heater

There are three main types of water heater:

  • storage water heaters
  • through-flow water heaters and
  • water heaters with plate heat exchangers.

Newer boilers are often equipped with through-flow water heaters. These consist of one or two water coils. The water in the coils is heated either in the storage tank or directly in the boiler.

The water quality decides the material

The quality of the water where you live determines the material that should be used for your water heater. If you have acidic or lime-rich water, a heater with indirect heating will perform well. This means that the heater is heated by shields on the outside of the container or that the heater element of the water heater is fitted in a protective tube.

Find out from your municipality the quality of the water you have in your area. If you have your own well, you can take a water sample and have it analyzed to make certain that you are investing in the right type of water heater.

A sacrificial anode protects against rust

Enamelled water heaters must have a “sacrificial anode”, which is a rod of magnesium, for instance, that protects the plates in the water heater against corrosion by the anode being consumed instead of the plates. If you have acidic water, the sacrificial anode will be consumed more quickly and will have to be checked and changed more often. Check the anode at least once a year.

Well insulated and of the right size

A new water heater should meet several important requirements. In the first place, it must be well suited for the needs of the household. In most cases, a storage heater with a volume of 200 litres will be sufficient for one family. If you have a bath tub, the water heater will have to be larger.

The water heater should be well insulated, since this will minimize the heat losses. The heat losses should not exceed 400 kWh/year or 40–50 W. Older water heaters are often poorly insulated and, in some cases, as much as 1200 kWh/year may be lost. It should also be possible to connect the water heater to other energy sources in order to improve its flexibility.

Temperature of at least 60°C

The temperature of the water in the heater should be at least 60°C in order to minimize the risk of dangerous legionella bacteria. 

Legionella bacteria occur naturally in drinking water, and their growth is promoted at temperatures of 30-40°C, but the bacteria are killed at 60°C. The bacteria are harmless in drinking water, but may cause pneumonia if they are breathed in with water vapour in a shower, for instance.

By installing economical-flow fittings, you can reduce the consumption of warm water without compromising on comfort. These enable you to lower significantly the warm water consumption.