By Steve Tawa

PHILADELPHIA (CBS) - Philadelphia Gas Works is increasing the rate it charges its customers for the next three months, because of natural gas market conditions.

Every three months, the city-owned gas utility makes price adjustments based on the cost of natural gas it purchases from suppliers:

“It is purely a consequence of market forces in action.”

Company spokesman Barry O’Sullivan points out the new rate reflects what PGW pays for the gas – from $1.36 per hundred cubic feet to $1.41:

“That isn’t any revenue that accrues to us. We pass the cost of the natural gas we buy onto our consumers without adjustment or markup or any change.”

The upward adjustment is the first in 20-months, during which consumers were paying less:

“Effectively for the last 5-6 quarters, we’ve been able to pass on decreases in the natural gas cost to our customers.”

He says the average PGW customer is still paying about $4.88 less per month than this time last year.