PORTLAND — The Maine Public Utilities Commission will hold a public hearing Wednesday night on a proposed $8.63 million natural gas rate increase that will affect thousands of customers in the greater Portland area.

Tonight’s hearing will begin at 5:30 p.m. in the Abromson Center on the Portland campus of the University of Southern Maine.

It has been 28 years since the area’s natural gas company, which is now called Unitil, asked for a rate increase. Unitil purchased Northern Utilities in 2008.

According to the PUC’s website, Unitil’s proposed rate increase would have the effect of increasing the rates of residential and small commercial customers proportionately more than larger commercial and industrial customers.