JEFFERSON CITY – A small group of determined senators tied up the Missouri Senate on Thursday with a filibuster against legislation that could reward utilities making improvements to their infrastructure with more consistent rate increases on their customers.

The legislation changing the way utilities are regulated drew intense opposition from some senators who said it would drive up costs for millions of residents and businesses. Supporters countered that rates are likely to rise anyway, and the bill would provide predictability by limiting annual average rate increases to 3 percent.

The Senate began debating the bill around 7 p.m. Wednesday and worked through the night as opponents made scores of quorum calls summoning sleepy senators who had retreated to their offices to return to the chamber. They finally paused for a break around 3:15 p.m. Thursday.

The opposition was led by Republican Sens. Doug Libla of Poplar Bluff, Gary Romine of Farmington, and Rob Schaaf of St. Joseph. They were joined Thursday by Democratic Sen. Maria Chappelle-Nadal, of University City.

The legislation "will not only raise rates on the little old lady down the street but businesses and industry across the state that provide jobs for our citizens," Romine told The Associated Press on Thursday.

Libla asserted that "money-hungry utilities (are) trying to take unfair advantage" of their customers.

As the filibuster droned on, Missouri Gov. Eric Greitens told reporters at the Governor's Mansion that he is reserving judgment on the evolving bill but supports "regulatory reform" and the efforts of the bill's lead sponsor.

"I think it's going to lead to more jobs and higher pay," the Republican governor said.

The bill would change the way the Missouri Public Service Commission regulates investor-owned electric and natural gas corporations such as Ameren Corp., Kansas City Power & Light Co., The Empire District Electric Co. and Spire Inc.

Such companies currently work through lengthy rate cases at the PSC. When utilities make infrastructure improvements between rate cases, the new facilities began depreciating immediately and the full cost of that capital investment is sometimes not fully recovered by utilities in subsequent rate cases, said Warren Wood, Ameren Missouri's vice president of legislative and regulatory affairs.

He said the legislation would encourage infrastructure investment by changing the accounting method for those improvements.

"It would benefit our customers with those investments to modernize the grid, and it would allow us to more accurately recover the costs so we could ramp up those investments," Wood said.

Ameren serves 1.2 million electricity customers and 127,000 natural gas customers in Missouri and is a major force at the Capitol. It's donated hundreds of thousands of dollars to candidates and political committees over the past few years and registered more than 40 lobbyists for its various subsidiaries.

Senate Majority Leader Mike Kehoe, a supporter of the bill, said Thursday that he wants to continue pushing toward an eventual vote but has no plans to employ a procedural move to shut off a filibuster and force a vote.

"The current system that we have that's outdated will allow for unpredictable and sometimes uncontrollable rate increases," said Kehoe, a Republican from Jefferson City. The bill "allows the utilities to perform the maintenance and infrastructure improvements they need to do with a predictable rate for both residences and businesses."

Supporters have offered various versions of the legislation this session. The latest version includes a provision giving the PSC the authority to more quickly lower rates for consumers to account for corporate tax cuts included in a new federal tax overhaul. Republican Sen. Ed Emery, of Lamar, said that provision could result in savings of $100 million for consumers.