Why heating stops without power – and what to prepare

Modern heating is electronically controlled. Without power the gas valve does not open, the burner does not ignite and the circulation pump moves no warm water to the radiators. Heat pumps, pellet boilers and many flat-level heaters stop too. With district heating it depends on the network and the substation in the building – the supplier can tell you.

After the outage the building cools slowly. How fast depends on insulation, outside temperature and how much it is aired. A well-insulated house holds heat much longer than an old, draughty one. That is why there is no general time figure. The aim is to keep the existing heat in a few rooms rather than creating new heat in dangerous ways.

Know your system before it gets cold. Note what type of heating you have, where the boiler and shut-off valves are, and the emergency number of the heating engineer or building management. Ask: does the system need power? Is there a wood stove that works without a fan?

During the outage, hold on to the warmth. Close doors to rooms you do not need and gather in one room, ideally a smaller one on the sunny side. Close curtains and shutters at night and let the sun in during the day. Air briefly and vigorously with the window wide open rather than leaving it tilted for a long time – that way you exchange the air without chilling the walls.

Keep people warm: several layers of clothing, a hat, warm drinks, blankets and sleeping bags. Pay special attention to older and sick people and to small children, because they cool down faster and often do not notice it themselves in time.

The greatest danger in a cold outage is not the cold but heating the wrong way. Gas hobs, ovens, barbecues, camping stoves, charcoal and outdoor heaters produce carbon monoxide. This gas is invisible and odourless and can be fatal. With headache, dizziness or nausea: get into fresh air immediately and call the local emergency number (112 in the EU).

Do not bypass controls, disable safety devices or connect gas or oil systems to backup power yourself. That is work for specialists. A wood stove with natural draught can heat without power – but only with an inspected chimney, dry wood and a working carbon monoxide alarm.

When the power returns, check whether the heating restarts by itself. If it shows a fault, use only the reset button the manual provides – and not repeatedly in a row. If that does not help, call the specialist. If you smell gas: do not operate any switches, leave the building and call the gas emergency service from outside.

Water expands when it freezes. In an unheated building, pipes can therefore freeze and burst during prolonged frost. The damage often only shows when they thaw and water suddenly escapes. Exposed pipes in the cellar, the garage and on outside walls are at risk first.

Clarify beforehand with the landlord, building management or specialist where the shut-off valves are and how pipes are drained in an emergency. If the temperature in the building drops towards freezing, the water is shut off and the pipes drained, as agreed beforehand.

The BBK points out that most heating systems also fail in a power outage. Ready.gov and the US health agency CDC strongly warn against using gas cookers, barbecues or generators indoors for heating.

This entry produces no heat – it helps you act early while there is still heat in the building. If it still gets too cold, for example for older or sick people, relatives with working heating or the municipality's warming centres are often a better solution than any improvisation.