Reruns — long the scourge of network TV — have become an endangered species.

As the webs roll out more and more original programming during summer months, it leaves less room than ever for repeats — especially of the drama variety. In their place, the networks are gambling with more original skeins and reality entries.

But hold your applause.

As unpopular as they are, repeats have traditionally been key to a broadcaster’s bottom line. Nets usually don’t make money on an episode until after its second run, since ad dollars from the initial airing usually cover the license fee, with little left to spare.

“The challenge becomes, unless you repurpose or put these shows on another platform, you don’t know how to amortize your costs,” says one network business affairs exec.

Hence the many starts and stops through the years as broadcasters flirted with original summertime fare, but always retreated back to their repeat diet.

That is, until now.

As the networks continue to see ratings erode — particularly in the summer — execs say repeats aren’t helping the bottom line the way they used to.

Shows such as “The O.C.,” “Gilmore Girls” and “NYPD Blue” — those with on-going sudsy storylines — typically flatline with auds the second time. That’s why ABC rarely repeats “Blue” anymore.

To build awareness, networks are airing more same-week encores of new shows — just as HBO has for years. Last summer, for example, Fox aired encores of “The O.C.,” and will do so again in June with its six new series.

Still, don’t look for Fox to run these episodes later on as traditional repeats.

It’s not that a net like Fox wouldn’t love to amortize its costs by doing so. But these days, it’s actually more cost effective to bring in original episodes of brand spankin’ new series. The ratings are higher, the ad rates are better and networks maintain some circulation — crucial to keeping viewers aware of what’s next in the web’s pipeline.

“You’re trading amortization for higher revenue and higher ratings — that’s the leading issue,” an exec says.

Nonetheless, the nets continue to look at other methods to recoup their programming costs. Besides same-week double runs, that includes repurposing shows on sister cable webs and partnering with advertisers to shoulder some of the overhead expenditure.

“When you’re dealing with very expensive shows, you’ve got to find a way to repurpose them,” says another webhead. “You also have to decide what’s going to be in your mix — how many shows are you going to air that are nonrepeatable? That includes soap operas, ’24’-style shows and reality shows.”

Of course, reruns won’t ever completely go away. The economics of running a broadcast network just don’t allow it. And given that few people actually watch every single episode of a given series, repeats are an important tool in luring new viewers to a skein.

That’s the summer strategy at ABC, which will again this season offer a heavy dose of its family friendly laffers “According to Jim,” “8 Simple Rules” and “My Wife and Kids.” None of these shows are megahits, so the network needs to take every shot it can at bringing more viewers into the fold.

It worked last year: The Alphabet started the season with decent numbers for its comedies, a feat partly attributed to the net’s summer repeat diet.

Comedy reruns also still come in handy when holes need to be filled — and given the current landscape, there are always gaps in a net’s sked.

“Comedies still repeat pretty well throughout the summer,” a network exec says. “When you’ve got a franchise comedy, that’s still your best utility player. They seem to be pretty resilient.”