How Much Will You Have to Pay for Hulu? Nothing. How Much Will You Pay for “Hulu Plus”? Good Question.

Is Hulu putting up a pay wall around its Web TV site? Nope.

Does Hulu want to charge people to watch Web TV? Yes.

Confused? Don’t be.

It’s pretty straightforward: Hulu, the joint venture between News Corp.’s (NWS) Fox, GE’s (GE) NBC Universal and Disney’s (DIS) ABC, doesn’t plan on charging people to watch the stuff it’s currently airing on the site–a mix of first-run shows from broadcast TV, a limited number of cable TV shows and a smattering of movies. But Hulu is trying to figure out how to create some kind of premium offering where you’ll pay for stuff that isn’t on the site right now.

That’s what Hulu’s backers have been saying for months, so it’s a little puzzling that News Corp. COO Chase Carey’s comments got folks worked up yesterday. Meanwhile, multiple sources familiar with Hulu’s plans tell me that…Hulu doesn’t actually have a plan yet, but it is trying to piece one together.

There are some pretty obvious ways to go here. Hulu could sell movies or TV shows on a pay-per-view basis, or it could sell subscriptions to shows it doesn’t offer now or to a deeper offering of shows it already has. You could call it “Hulu Plus” (no charge for that one, guys).

If you’re a fan of Fox’s “Family Guy,” for instance, Hulu is only of limited help: The site only has the most recent five episodes. So how much would you pay to watch the rest of them?

If you don’t have an answer for that, don’t worry–Team Hulu doesn’t know, either. Nor can they tell you if airing free shows on Hulu has cut into other revenue streams like broadcast TV advertising or DVD sales, even though “we’ve done a thousand regression analyses on this,” says an industry executive involved in the site.

Do bear in mind that this was a problem Hulu’s backers didn’t really envision when they were dreaming up the site; at the time, they were most concerned with building a video site that would allow them to barter with Google (GOOG) and Apple (AAPL).

Now they own one of the biggest video sites on the Web, one they say is performing ahead of plan. And Hulu is selling enough advertising that it’s coming close to reaching break-even, according to executives I spoke to this week.

But at the very least, adding a pay component to Hulu helps mollify those who fear the site is cannibalizing their existing businesses. Or who simply want another revenue stream. And a pay element dovetails with Hulu’s interest in joining up with the “authentication” movement pushed by cable guys like Comcast (CMCSA) and Time Warner (TWX).

Meanwhile, here’s the use case for Hulu that its backers originally envisioned–“catch up viewing.” I was on a plane when last night’s episode of the “The Office” aired, but I can watch the whole thing–with ads I can’t skip–on my laptop today. And so can you: