do a power of good

do (one) a power of good

To be very beneficial to one. If you're feeling sad, getting out in the sunlight should do you a power of good.
See also: good, of, power
Farlex Dictionary of Idioms.

do someone a power of good

 and do someone a heap of good
Rur. to be very good for someone. You should take a vacation. It'd do you a power of good. Just hearing your voice does me a heap of good.
See also: good, of, power
McGraw-Hill Dictionary of American Idioms and Phrasal Verbs.

do somebody/something a ˈpower/ˈworld of good

(old-fashioned) do somebody/something a lot of good; benefit somebody/something: She’s under a lot of stress at work, and a few days at the coast would do her a power of good.
See also: good, of, power, somebody, something, world
Farlex Partner Idioms Dictionary

do a power of good, to

To effect a great improvement. This somewhat unsophisticated turn of phrase uses “power” in the sense of “much” or “a great deal.” For example, “Those vitamins will do her a power of good.”
See also: of, power
The Dictionary of Clichés by Christine Ammer
See also:
  • do (one) a power of good
  • do someone or something a power of good
  • do somebody/something a power/world of good
  • do (one) a/the world of good
  • do (one) a heap of good
  • a world of good
  • be good for (someone or something)
  • be good for something
  • do no good
  • as good as it gets