Smaller customers of Madison Gas & Electric could see the fixed portion of their monthly bill jump dramatically under a sweeping rate change proposal from the investor-owned utility.

Right now, homeowners and renters pay MGE a set charge of about $10 a month (called a "customer charge" on typical MGE bills) regardless of how much electricity they use. That would increase to $49 by 2016 under a two-year rate plan that is now before the state Public Service Commission.

For natural gas customers, the monthly fixed charge is proposed to go from $12 to $21 in 2015.

MGE says the changes are needed to ensure the company doesn’t have to rely so much on sales to its larger industrial customers to fund operations. About 90 percent of MGE customers are residential or small commercial users.

“Under MGE's current rates, lower usage customers are not paying an appropriate share of the fixed costs of service,” MGE’s rate analyst, Steve James, said in testimony to the PSC earlier this month, adding that the fixed charges could rise to $69 in 2017.