The CW, which went dark this summer with a repeat-riddled lineup, turned on the lights Tuesday with a decent debut for Sarah Michelle Gellar drama “Ringer” — the first of 27 new series set to bow on broadcast TV this fall.

Nielsen estimates that “Ringer,” in which Gellar plays a woman on the run who assumes the identity of her identical twin sister, averaged a 1.2 rating/3 share in adults 18-49 and 2.84 million viewers overall in the 9 o’clock hour. In a good sign, viewership in all categories either held steady or gained slightly in the second half-hour.

Also, it won its hour among adults 18-34 in major cities including New York, Los Angeles, Chicago and Philadelphia. Though a

nice improvement over last year’s debut of “Life Unexpected” (0.8/2 in 18-49, 1.65m) in the same timeslot and comparable week, CW was probably hoping that the television return of Gellar, whose “Buffy the Vampire Slayer” had a lengthy run on the WB and then UPN, might pop a bit more and lift the network above its typical ratings levels.

CW’s most popular series, “The Vampire Diaries,” opened its second season last fall to a 1.6 rating in 18-49. The 1.2 for “Ringer” matched the debut of last fall’s CW drama “Hellcats” (later canceled) and was below that of “Nikita” (1.4), which is back for a second season.

Still, for a net that averaged well under 1 million viewers this summer, it’s an acceptable opening. One of the stated goals of new CW prexy Mark Pedowitz has been to add firstrun programming to the net’s lineup next summer so it will have a base of viewers to which it can promote its fall fare.

Next week, “Ringer” will face tougher competish from Tuesday premieres on the Big Four. CW is offering viewers two more chances to catch the premiere episode of the drama — Friday at 8 p.m. and Monday at 9.

Originally developed for sister network CBS, “Ringer” skewed older than typical CW fare, drawing a higher rating in adults 25-54 (1.3) than in 18-34 (1.1). That’s not a bad thing for the net, which is still targeting primarily women 18-34 but knows it needs to recruit viewers in other demo categories as well.

The older audience lifted “Ringer” in the total-viewer category, with its premiere aud the best for a CW show in the timeslot in three years.

Also Tuesday for CW, “90210” opened its third season on a new night with a 0.9/3 in 18-49 and 1.61 million viewers overall — down a bit from last year’s Monday debut (also a week before the start of the season).

Elsewhere Tuesday, NBC launched the third season of “Parenthood” at 10 p.m. (2.2/6 in 18-49, 6.29m), down 19% from last year, when it bowed in the comparable week. It aired Tuesday behind the performance finale of “America’s Got Talent” (3.8/10, 13.67m), which was down just 3% year to year and was easily the night’s top show.

While NBC has seen some summer success with “America’s Got Talent” and drew record viewership for its NFL games last week, it too has been quiet this summer in the scripted arena — which may have hurt its first scripted premiere of the fall. The Peacock generated higher than a 1 rating in 18-49 with a scripted series just nine times between Memorial Day and Labor Day.

Each 18-49 ratings point this season represents roughly 1.28 million viewers, down from the 1.32 million of last year, according to Nielsen’s latest TV universe estimates.