Energy savings: how to reduce by half the energy used by your boiler




Energy savings: how to reduce by half the energy used by your boiler

In a lot of homes, the hot water boiler has quickly become the biggest energy user. The average annual usage of the appliance amounts to 1,900 kilowatt-hour (kWh), in other words, more than half of the total energy used by an average Flemish family (3,500 kWh). Luckily, we can significantly reduce the energy usage of any type of hot water boiler by taking a few simple steps.


1. Insulate your hot water boiler

Heat loss occurs even when no hot water is being used, so a boiler will still regularly heat the water. This “standstill loss” or “no-load loss” amounts to about 30 to 60 watt, depending on the boiler’s water capacity (the larger the boiler, the greater the heat loss). An appliance with 150 litre capacity will easily use over 500 kWh per year to compensate for this heat loss, i.e. about a quarter of its total energy use.


To equip a boiler with good thermal insulation can significantly reduce this heat loss. Yet most hot water boilers have only limited insulation. This is why it’s a good idea to wrap your boiler in insulation material such as rock-wool, Styrofoam or insulation blankets. Insulating a boiler after it has been fitted is very simple and generates substantial energy savings. In theory, energy loss could be prevented entirely, though in practice, maximum insulation is often restricted by the space available around the boiler.


2. Insulate water pipes

Heat loss also occurs via the water pipes that run to and from the boiler. Heat loss can be further reduced by insulating the first two meters of the pipes. Both cold and hot water pipes should be wrapped up. Insulating the water pipes reduces the standby usage by about a third.


3. Save energy and water: fit a water-saving shower head

A water-saving shower head uses about 30% less water, without any impact on comfort. Of course, this is a double winner as it also means that 30% less water needs to be heated.


4. Lower the temperature

Users can set the temperature of the hot water boiler themselves, up to a maximum of 90 degrees Celsius. The higher the temperature, the greater the volume of hot water the boiler can provide, as the hot water gets mixed with cold water in order to obtain the ideal temperature of about 37 degrees. But a higher temperature also means a higher energy use.


If you lower the thermostat, you will save about 5% energy for every 6 degrees. The most energy-efficient temperature is 60 degrees Celsius. Lower temperatures are not recommended as they increase the risk of bacteria (legionella bacteria) developing in the boiler.


5. Does a timer help save energy?

It’s often advised to fit a timer to the boiler so that the water is only heated when it’s needed. However, this doesn’t always save energy as more energy is required to heat the cooled water back to the set temperature. Besides, the timer itself uses electricity. A timer may be useful when the boiler is badly insulated, though if this is the case, then it would be much better to insulate the boiler (see above).


If you don’t need hot water over a long period (for example if you’re away over the weekend), then it’s definitely worth switching off the boiler, as the energy required to increase the temperature once the water in the boiler has cooled to room temperature remains the same.


6. De-scale the boiler

Limescale on electrical resistors (which heat the water) reduces the hot water boiler’s energy efficiency. Consequently, it’s recommended to de-scale the boiler every two years.