blackout vs power failure

blackout and power failure both are nouns.

Word	Noun	Adjective	Verb	Adverb
blackout	Yes	No	No	No
power failure	Yes	No	No	No

As nouns, power failure is a hypernym of blackout; that is, power failure is a word with a broader meaning than blackout:

Other hypernyms of blackout include power outage.

blackout (noun)	power failure (noun)
a momentary loss of consciousness	equipment failure resulting when the supply of power fails
partial or total loss of memory
the failure of electric power for a general region
darkness resulting from the extinction of lights (as in a city invisible to enemy aircraft)
a suspension of radio or tv broadcasting