Completely switching off your heating boiler is rarely a good idea, even when you go on holiday. Modern heating systems are designed to operate efficiently and safely, even when you’re not at home.
The terms boiler and water heater are often mixed up, but they refer to very different appliances. It’s important to know which device does what so you can choose the right settings during your holiday.
| Appliance | What it does | Additional info |
|---|---|---|
| Central heating boiler | Heats the water that flows through your radiators | Provides home heating; runs on gas, electricity or oil |
| Hot‑water boiler | Supplies hot water for taps and showers | Separate from radiators; may be integrated into the heating boiler (combi boiler) or stand alone |
Heating boiler: set to 12°C, do not switch off completely
Why not turn it off entirely?
1. Moisture problems
Below 12°C, moisture condenses on cold surfaces, leading to mould and dust mites, especially in poorly insulated homes.
2. Freezing risk
In winter, water pipes can freeze and burst. Even outside winter, nights in Belgium can get very cold. Repair costs far outweigh any energy savings.
3. Preventing malfunctions
Many boilers automatically run the pump from time to time, even without heating demand. This prevents components from seizing during long periods of inactivity. This function uses almost no energy or gas/heating oil, but can save you expensive repairs. If you switch the boiler off completely, this protection no longer works.
4. Safe with modern, well‑maintained boilers
In Brussels, gas boilers must undergo mandatory maintenance every two years. They also have overheating and backdraft safety systems that shut the appliance down if something goes wrong.
5. Comfort when you return
It’s pleasant to come home to a warm house. Heat loss depends on your home’s insulation. With a programmable or smart thermostat, you can restart heating the day before you return. This is both comfortable and energy‑efficient—provided the boiler remains on.
Did you know?
When the thermostat is set to a low temperature, the boiler does not use energy to heat your home unless it gets extremely cold and the indoor temperature drops below the minimum setting. There may be a tiny amount of consumption for pump or frost‑protection functions.
Before leaving
Set your thermostat to at least 12°C while you’re away. This prevents problems and still saves a lot compared to the usual 19–21°C. The heating won’t run unnecessarily, but your home stays protected from cold and moisture.
Smart thermostat? Many modern thermostats have a holiday mode or frost‑protection mode that automatically maintains the right minimum temperature. You can also program the heating to restart just before you get home.
Exception for older models
If you still have an old gas boiler with a pilot light, switching it off can make sense. The pilot light burns gas continuously, which is not compatible with an energy‑efficient home.
Hot‑water boiler: switching it off does save energy
Why turning it off is worthwhile
A traditional hot‑water boiler keeps water constantly at temperature so you have hot water immediately. This uses a lot of energy, especially when no one is home to use it. Turning it off during your holiday reduces unnecessary consumption and saves both energy and money—without any risk.
This also applies to small kitchen boilers or close‑in systems that provide instant hot or boiling water.
Combi boiler: nothing to do
If you have a combi boiler without a storage tank, you can leave without switching anything off. This type of appliance heats water only when you o the tap and does not keep a hot reserve. You can simply leave it running as usual during your absence.
FAQ
What should I do with a hybrid heat pump when I’m away?
For a hybrid heat pump, it’s enough to set the thermostat to 12°C. The system will automatically choose the most efficient energy source (electricity or gas). Make sure to keep the smart control activated: this ensures the installation runs at its best, even while you’re on holiday.
Is it better to lower the boiler temperature instead of switching it off completely?
No, that’s not a good idea. Between 25°C and 55°C, legionella bacteria can grow. Keep the boiler set to 60°C or switch it off completely while you're on holiday.
I live in an apartment. Should I also turn off my boiler when I go on holiday?
In an apartment, the temperature tends to stay more stable because the surrounding homes provide extra insulation. Still, you should keep the heating at a minimum of 12°C while you’re away, especially if several neighbours are also absent.