Avista Corp. won Idaho Public Utilities Commission approval for a multiparty settlement over its two-step electric and natural gas general rate cases in Idaho.

The approved rates will increase the company's annual electric revenue by $12.9 million, or 5.6%, effective Jan. 1, 2018, and $4.5 million, or 2.3%, effective Jan. 1, 2019. For natural gas, the settlement provides for revenue increases of $1.2 million, or 1.9%, in 2018, and $1.1 million, or 1.8%, in 2019, Avista said in a Dec. 29 news release.

The increases are based on a proposed 9.5% return on equity with a common equity ratio of 50%.

The average residential electric customer using an average of 910 kWh per month will see the monthly bills increase by $5.22, or 5.9%, to $93.34, effective Jan. 1, 2018. The same customer would see a monthly increase of $2.16, or 2.3%, for revised monthly bills of $95.50, effective Jan. 1, 2019.

Natural gas residential customers consuming 63 therms per month will see their monthly bills increase by $1.13, or 2.1%, to $53.74, effective Jan. 1, 2018. From Jan. 1, 2019, the same customers would see a monthly increase of $1.09, or 2%, to a revised monthly bill of $54.83.

The 2018 rates for both electricity and natural gas include an increase in the basic monthly charge to $6 per month.

The approved rates are less than the originally filed electric base rate increase of $18.6 million, or 7.5%, for 2018, and $9.9 million, or 3.7%, for 2019. For natural gas, Avista requested hikes of $3.5 million, or 8.8%, for 2018 and $2.1 million, or 5%, for 2019, which were based on a proposed 9.9% return on equity. The initial request was filed in June, and a settlement accepted by all parties except for two environmental groups was reached in October. (Idaho PUC Final Order No. 33953)