The Minnesota Public Utilities Commission unanimously agreed Thursday to terminate the unsuccessful experiment to promote conservation by making CenterPoint Energy customers pay higher rates as they used more natural gas.

The program, which began in July 2010, has been suspended since October, when critics complained it was unfair to many customers. CenterPoint later gave refunds to 370,000 Minnesota customers who were overcharged.

The experiment with five escalating rates rewarded four out of five customers who used modest amounts of natural gas each month. But 20 percent of customers landed in highest-priced rate tiers, including some who were bumped into those tiers because the utility's "monthly" billing period sometimes exceeded 31 days.

CenterPoint, conceding the program had unintended consequences for some customers, had supported ending the program for good.