The agreement provides for three annual rate increases of 4.9% in 2013, 2014 and 2015, followed by a rate freeze in 2016.

Effective 01 May 2014, North Dakota customers will see an increase of about $1 in their monthly bills from the interim rate level.

Xcel Energy company Northern States Power Co.-Minnesota president and CEO Dave Sparby said the rate request will minimize customer bill impacts, provide more rate predictability and avoid having to pass on to customers the costs of additional rate proceedings during the plan term.

"At the same time, it allows Xcel Energy to finance needed upgrades of its nuclear and other power plants as well as expansion of its transmission grid," Sparby added.

"These investments are needed to continue providing reliable and safe electricity to our North Dakota customers well into the future."

Xcel’s 90,000 North Dakota customers will also get refunds totaling about $3.6m, or $19 this summer, as the interim rates in effect since February 2013 until 01 May 2014 were higher than the final rates.

In addition, customers would also receive refunds if the company’s weather-normalized earnings exceed commission-authorized levels in any year during the four-year rate plan.