The room boom in Charleston is starting to cut into hotel occupancy rates.

Charleston County hotels sold about 8,000 more room nights in April than they did the same month a year ago, but because more hotel rooms have been built, the percentage of filled rooms declined slightly.

Occupancy slipped 0.3 percent to 84.9 percent over April 2012, according to a new report by the Office of Tourism Analysis at the College of Charleston.

This was “solely due to inventory increase,” said Perrin Lawson, deputy director of the Charleston Area Convention and Visitors Bureau.

Downtown Charleston saw its first new hotels in years come online earlier in 2013.

The 120-room Holiday Inn Charleston Historic Downtown on Meeting Street and the 153-room Holiday Inn Express, a former Best Western that was redeveloped, opened over the winter, adding to the number of rooms available.

Others have opened in North Charleston, mostly around the Ashley Phosphate Road area.

Looking out, at least 1,500 more rooms have been proposed, mainly across peninsular Charleston. In response, the city is looking at updating its rules governing accommodation businesses in and around the historic district.

April is traditionally a strong month for the region’s hotel business, with events such as the Cooper River Bridge Run and the Family Circle Cup fueling demand for places to stay.

That was borne out in the financial figures in last month’s report. Even with the extra rooms, the average daily rate jumped 5 percent from last year to $148.07, the Office of Tourism Analysis found.

Also, revenue per available room, or “revpar,” climbed 4.8 percent to $125.87, the highest on record. That figure is calculated by multiplying the average daily room price by the occupancy rate.

Peninsular hotels and lodgings in East Cooper saw their percentage of vacant rooms edge up in April. It was the opposite in West Ashley and North Charleston.

For the year, the county hotel occupancy rate is down 2 percent.

Reach Warren L. Wise at 937-5524.