Some cash-strapped athletic departments outside the Power Five conferences have started to use beer sales as an alternative revenue stream -- and more could soon be following suit.

While beer drinking is a common sight at tailgate parties outside of college football stadiums, a growing number of schools are bringing the party inside, opening taps in concourses that traditionally have been alcohol-free zones.

North Texas, SMU and Troy University will begin beer sales to the general public this season. They're among 21 on-campus football stadiums where any fan of legal age can grab a brew. That's more than twice as many as five years ago.

There will be 21 on-campus stadiums where beer sales will be permitted this season. According to a survey, about half of those schools' concessions revenue is derived from alcohol sales. AP Photo/The Star Tribune, David Joles

"Every institution is looking at how they can increase revenue streams, and alcohol is one of those," said Jeff Schemmel, president of consulting firm College Sports Solutions LLC. "Everything is on the table."

Most schools continue to keep alcohol restricted to premium seating areas, if they allow it at all. But offering alcohol is increasingly attractive for some campuses, especially as schools look for ways to keep fans from staying at home.

They're also encouraged by the schools that were among the first to sell alcohol and didn't report an increase in bad behavior from students and other fans.

There are 11 municipal stadiums where FBS teams are tenants and alcohol is available to the general public. The municipality usually keeps most, if not all, of the alcohol proceeds. The NCAA does not sell alcohol to the general public at its championship events. Schools and conferences are allowed to make their own policies.

According to an Associated Press survey of the 21 beer-selling schools that own and operate their stadiums, about half their concessions revenue is derived from alcohol. All but four of those schools are in conferences outside the Power Five that don't earn significant television money.

Troy athletic director John Hartwell estimated that beer would account for $200,000 in commissions this season. According to its contract with concessionaire Sodexo, Troy will receive 43 percent of gross beer sales at its 30,000-seat stadium, or better than $2 for every $5 beer.