A sudden power outage or technical defect can paralyze card devices from one second to the next. In the event of power outages, card payment is no longer possible.
It makes the most sense to have the money ready in small bills. In addition to cash, citizens should store a number of other things at home. These include a flashlight, a camping stove and a battery-powered radio. A complete checklist in case of a blackout can be found here. (tt) The German Federal Office does not provide precise information on how much money should be stockpiled.