. 2016 compared to 2015 net income increased $ 16.5 million primarily due to lower other operation and maintenance expenses , higher net revenues , and a lower effective income tax rate , partially offset by higher depreciation and amortization expenses . net revenue 2017 compared to 2016 net revenue consists of operating revenues net of : 1 ) fuel , fuel-related expenses , and gas purchased for resale , 2 ) purchased power expenses , and 3 ) other regulatory credits