It’s been tough for performing arts groups, but it’s about to get tougher.

The cost of renting the Memminger Auditorium, the historic venue run by Spoleto Festival USA, is about to jump 30 percent, according to sources at the festival.

The rate hike begins next month.

Since opening last May after a $6 million renovation, the Memminger has become a hot spot for local performing arts groups, including the Charleston Symphony Orchestra, Charleston Stage, and many events featured at the MOJA Festival.

CSO officials have said the 350-seat Memminger is the preferred venue compared to the 2,700-seat Gaillard Municipal Auditorium, because it’s smaller, more intimate, and less costly.

Now the rent is going up.

The reason is not because of a historic economic meltdown. The reason is the cost of operating the historic venue. It’s proved to be more than expected, says Susie Prueter, Spoleto’s assistant production manager.

“It’s a learning curve,” she says. “We’re trying to keep costs as low as possible.”

Spoleto’s goal, Prueter says, wasn’t to make money but to create a “community venue” shared by area nonprofits. Financially, Spoleto’s goal is the break even.

Thus far, it hasn’t. The air conditioning alone costs around $60,000 a year.

Here are the new rental rates. Monday-Thursday: $800 per day. Friday-Sunday: $1,100 per day. A full week: $3,500.

It’s still a deal if you want a cozy audience. Renting the Gaillard will run you about $2,000 a night.

Venue expenses are one reason Charleston Stage had to lay off three full-time employees this week as well as issue a 6 percent pay cut for its entire staff.

The theater company, Charleston’s largest, has had to lease the Memminger and CofC’s Sottile Theatre while the Dock Street Theatre is being renovated until 2010.

Leasing them has proved to be “more than double” the previous cost, says Julian Wiles, founder and director of Charleston Stage.