As far as I know, the ECB is not claiming that the digital Euro will be able to operate without electricity, instead they are saying that they can operate offline without a constant internet connection.......

1) As far as I am aware, Ursula von der Leyen said that if the EU CBDC was up and running, there would have been no problems in Spain during the power outages. I will try to find out exactly what she DID say.

2) As for power outages, I am confident that we can expect many more such events in the future, as Europe heads towards 'Net Zero' and Agenda 2030. Spain is already well-advanced in terms of wind and solar power. I understand that the Spanish outages were caused by a spike in output when the wind picked up, which blew the fuses or some such. Again, I am vague on the details & will try to find out more. 

3) My original question was posed because I can send BTC from my phone to somebody else's phone. Both are obviously battery-powered. So where does the need for electricity kick in?

4) It is easy to generate electricity - I am in the UK and bought a generator years in anticipation of the 'Net Zero' agenda and all the other horrors the globalists have in store for us. I'm guessing American readers will be more insulated against all this nonsense and may not be as familiar with the concept of 'fifteen-minute cities', the banning of gasoline and diesel cars, the banning of commercial air travel etc that are part of Agenda 2030. About three years ago, Schipol airport in the Netherlands cut flights by 15% to 'save the planet', and France has banned flights of less than 1.5 (or 2.5) hours if there is a rail alternative.
Europe is about to (literally) enter the dark ages. So discussions about the availability of electricity are becoming more relevant.