This really is a simple question. At lines close to pkem "buy" the 1/2 goal if you pay less than 40 cents. Example: pkem -120 vs. -1/2 +123. Here the -1/2 is the stronger play since it would be roughtly equivalent to pm em -117 using the 40 cent adjustment.
Go over to pinnaclesports.com. Tonight they are dealing:
Bruins -1/2 -110, Bruins pkem -148
Islanders -1/2 +115, Isl pkem -125.
See the 38 and 40 cent difference? So if the best rogue lines you could get were Bruins -1/2 EV or Bruins pkem -136, you would play them -136 since it only "costs" you 36 cents to "buy" the 1/2 goal vs. the best puckline.
Now, you need to be careful if the line is not close to pkem. In general the 1/2 point "buy" is worth progressively more than 40 cents as you move away from pkem type lines.
Disregard all the posters that say "split it 50/50, look at spcific games, etc". I can assure you these are all the wrong answers.
Get used to going over to Pinnacle.com and they typically deal their MLs consistent with their puck lines, so their split lines will easily educate a hockey bettor exactly how much the 1/2 goal is worth on specific spreads away from pkem. Like a Baseball R/L you do need to be careful with how and low total games.