The price of natural gas has gone up.

Effective Tuesday, the area¡¯s three natural gas companies raised utility rates between 12 percent and 30 percent.

Columbia Gas Co. rates for residential customers increased 12 percent, on average, from $12.76 per thousand cubic feet to $14.38. That means the average residential bill increased from $104 last quarter to $114.

Matt Pitzarella, Columbia Gas spokesman, said the increase shouldn¡¯t have much effect on most residential customers at this time of year, when average usage is less. A typical summer bill should be about $50 per month, Pitzarella said. Columbia Gas has more than 410,000 customers primarily in western Pennsylvania, including Beaver, Lawrence and Allegheny counties.

The gas cost rate is not a profit-making increase, but instead represents the actual cost for companies to buy natural gas supplies for customers, Pitzarella said. State law requires utilities to pass on dollar-for-dollar costs.

Pitzarella said there are several reasons for the increase, including the rising cost of crude oil, which has reached more than $100 a barrel, boosting demand for other, less expensive fuels.

Equitable Gas, which serves more than 274,000 customers in southwestern Pennsylvania, raised its rates 18 percent, from $11.81 to $13.97, increasing the average residential bill from $134.40 last quarter to $154.32. And Dominion Peoples¡¯ average monthly bill increased 30 percent, with rates up from $9.53 to $12.44. Monthly bills on average increased from $102.16 to about $124 per month, said Elmore Lockley, company spokesman.

Lockley said rates have been set based on what is happening in the nationwide market. He said another significant reason for the increase is the past winter was colder than normal, which had an effect on natural gas supplies as consumption increased. Dominion serves 357,000 customers in southwestern Pennsylvania, including Beaver, Lawrence and Allegheny counties.