The most commonly used 1NT Opening bids fall within the range of 10 - 18 HCP :

Ron Klinger (in his book 'The Power System', Modern Bridge Publications, 1993) categorically states that : "As far as the object of the bidding is to locate the best contract for your partnership

ALL (above) NO-TRUMP RANGES ARE WRONG"

He makes the following points.

1. All above NT ranges are fine as a sound basis for finding a Game or Slam contract, but their weakness lies in finding the best partscore.
   The weaker the no-trump, the more often the partnership will land in the wrong partscore!

2. Weak 1NT Openings (in the 10-15 HCP range), although good in terms of pre-emptive value and damaging to the Opponents, are commonly doubled for penalties, which opposite a weak partner can cost the side dearly.

3. If you are lucky enough to be left in a 1NT contract (regardless the 1NT HCP range) you will statistically on average receive a 65% Match points score (which is of course very good).
   Therefore Enemy interference over a 1NT Opening bid is fierce and supported by more Bidding Conventions than for any other purpose : Astro (three varieties) - Becker - Brozel - Canapé - Cappelletti - DONT - Landy - Ripstra - RCOs - TRASH

4. The agony of the 19-20 (or 18-20) points balanced hands.
   Such strong hands are commonly opened with 1♣ or 1♦, then passed all around (when Partner's hand is 5 points or less), resulting in a poor score.
   The alternative opening at the 2 level is too high opposite a Partner with a very weak hand and commonly attracts a minus score.

Klinger therefore recommends the Power 1NT Opening with 17-20 points :

After more than 20 years of experience and success both Nationally and Internationally with this Opening (as part of his Power System) Klinger reports the following advantages :