Power cut at home: what still works and what to prepare

Every year the Bundesnetzagentur records how long the electricity supply in Germany was interrupted on average. The indicator is called SAIDI EnWG and states the average supply interruption per connected final consumer within a calendar year (Bundesnetzagentur). For 2024 the authority reports 2.43 minutes (Bundesnetzagentur), after 2.42 minutes (Bundesnetzagentur) the year before. That is little, and it is the reason most households rarely think about the subject. The average, though, says nothing about how a single outage feels: it spreads the total outage time across all connections. A household that is actually affected does not sit in the dark for a good two minutes; it goes for years without any outage and then has one longer one.

The Federal Office of Civil Protection and Disaster Assistance describes the range openly: as a rule power cuts are resolved within a few hours (BBK). At the same time the authority notes that in emergency situations with large-scale damage it can indeed take days until electricity is available again (BBK). The whole of preparation sits between those two sentences. For the normal case a charged power bank and a torch you can actually find are enough. For the rare long case you need a few more things - and above all the knowledge of what in your own home depends on the mains at all. Hardly anyone carries that list in their head, because technology works invisibly and only speaks up when it is missing.

German law requires providers to make arrangements so that end users can set up free-of-charge connections initiated by dialling the Europe-wide emergency number 112 or the additional national emergency number 110 (Section 164 of the Telecommunications Act). The law also stipulates that emergency calls are to be established with priority over other connections (Section 164 of the Telecommunications Act). That duty applies to the service, not to the socket in your living room: it makes sure an emergency call has right of way in the network as soon as a connection is established at all. It says nothing about the power supply in the house, and that is precisely where the problem sits during an outage.

In its strategy paper on the resilience of telecommunications networks the Bundesnetzagentur writes that during a power cut it is regularly no longer possible to make emergency calls (Bundesnetzagentur 2022). The reason is the same as for the fixed line: without a continuous network there is no path to the control centre, and permanently installed backup power solutions exist only at a limited number of the operators' technical sites (Bundesnetzagentur 2022). At the same time the authority names the bright spot: mobile networks can serve a large number of users at once, and thanks to integrated and external batteries the terminal devices still offer the possibility of communication at least for a limited time in the event of a power cut (Bundesnetzagentur 2022). Anyone who wants to make a call in an emergency therefore needs a charged phone and patience while the connection is set up.

Preparedness sounds like a shelf in the basement, but it is mostly about order. The BBK names the core in one sentence: make sure that the batteries in your laptops, mobile phones and telephones are charged, or keep charged spare batteries ready (BBK). Anyone who charges the phone in the evening instead of running it down to the last percent has already done the largest part. What helps beyond that fits on a short list: light, information, communication, cash, warmth. Everything else is comfort. How to look after the battery in everyday use is described in the article when the phone battery does not last.

For the long case the BBK gives two figures worth remembering: you should be able to look after yourself for ten days if possible (BBK), and a supply for at least three days already helps a great deal (BBK). That explicitly includes a battery-powered radio or a wind-up radio so that you can follow announcements from the authorities during a prolonged power cut (BBK), and cash, because during a power cut the cash machines stop working too (BBK). The supply is not a special purchase but the normal shopping list with a little lead time: whatever gets eaten anyway goes into the cupboard and is used up in order.

That leaves the question of backup power for the router. A small uninterruptible power supply keeps the router and DECT base alive for a while, and in a short outage that is exactly the right thing: the phone stays reachable, the doorbell rings, the alarm system keeps logging. For the long case the limitation from the strategy paper applies: without a network outside the door, your own battery achieves little. In our smart home consulting we look at which devices in your home actually depend on the router and decide with you what is worth protecting and what can be left alone.

The return is undramatic, but it has an order that saves trouble. Switch large appliances back on one after another instead of letting everything start at the same time. The router usually needs a few minutes before the connection is back up; that is normal and not a defect. Only after that do the smart home hub, cameras, doorbell and network storage report back, and in that order, because each of these devices needs the router. Anyone who opens the app immediately after switching the power back on and sees nothing has usually just looked too early.

A short tour is worth it afterwards. Clocks on the oven, the alarm clock and the heating controller rarely set themselves; schedules for light and heating only run again once the hub knows the time. Check whether the camera recordings are running again, whether the video doorbell rings and whether the home emergency call unit reports its normal state. The fridge needs no attention as long as the door stayed shut - after that your nose decides, not the clock. Writing this tour down once saves half the time on the next occasion.

That classification is the reason why this article contains no equipment list for weeks on end. The likely case lasts hours, and for hours a charged power bank, a torch, a radio and the certainty that the front door can be opened are enough. Everything beyond that is a deliberate decision for the unlikely case, and it may be a small one. Once the list has been worked through, experience suggests it only needs to be reviewed once a year.