ST. PAUL (AP) - Several environmental groups are asking Xcel Energy to rethink the way they charge people for electricity.

The groups are asking Xcel to switch from a flat rate to a system that charges more per kilowatt hour as use increases.

The groups believe such a system would improve energy conservation.

Will Nissen, a policy associate for Fresh Energy, says the system would also benefit low-use customers. They say Xcel is already using such a system in Colorado.

Xcel says they're reviewing the proposal.