(a) The tax impact of each line item was calculated using Avista Corp.'s statutory tax rate (federal and state combined) of 23.05 percent.
(b) Electric utility margin (operating revenues less resource costs) increased for the first quarter and was impacted primarily by the following:
General rate increase in Washington, effective April 1, 2020.
Customer growth contributed additional retail electric revenue.
In the first quarter of 2020, we recorded an accrual of $1.4 million for customer refunds related to our 2015 Washington general rate case.
For the first quarter of 2021, we recognized a pre-tax benefit of $4.3 million under the Energy Recovery Mechanism (ERM) compared to a pre-tax benefit of $5.2 million for the first quarter of 2020. For the full year 2021, we expect to be in a benefit position under the ERM within the 75 percent customer/25 percent Company sharing band.