power failure vs power outage

power failure and power outage both are nouns.

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

As nouns, power failure and power outage are synonyms defined as:

power failure and power outage: equipment failure resulting when the supply of power fails

power failure (noun)	power outage (noun)
equipment failure resulting when the supply of power fails	equipment failure resulting when the supply of power fails