Losing power in the UK vs US: what's more common?

Solution 1:

"Power cut" is certainly the most common in the UK, as seen in the comments. Lexico Oxford Dictionaries gives the phrase the "British" tag.

On Google News, almost all of the news is UK stories, and it's the same story ;-) for power outage in the US.

As for blackout being used as a term for a mass outage in the UK, the fairly recent mass power cut that affected the nation is indeed referred to as a blackout more often than power cut.

"Power outage" is often used to refer to a more local failure, whereas "Power failure" is almost never heard, clearly shown on NGrams:

"Blackout" is also seemingly used to mean a wide-scale outage in the US, as shown in News as well.

"Power failure" doesn't seem that popular either, and as it's a UK term, "power cut" is close to nonexistent. (where "cut" is used, it's usually published by a UK news site).