self-starter vs powerhouse

self-starter and powerhouse both are nouns.

Word	Noun	Adjective	Verb	Adverb
self-starter	Yes	No	No	No
powerhouse	Yes	No	No	No

As nouns, powerhouse is a hypernym of self-starter; that is, powerhouse is a word with a broader meaning than self-starter:

Other hypernyms of self-starter include ball of fire, fireball, human dynamo.

self-starter (noun)	powerhouse (noun)
an electric starting motor that automatically starts an internal-combustion engine	an electrical generating station
an energetic person with unusual initiative	a team considered to be the best of its class
	a highly energetic and indefatigable person