Yes, BECU's HELOC interest rates are based on the prime rate plus a margin. The exact margin can vary throughout the life of the loan based on factors like your credit score, the loan-to-value (LTV) ratio of your home, and the amount of the credit line, as well as the prime rate.
The prime rate is a benchmark interest rate used by banks and credit unions, which is influenced by the federal rate set by the Federal Reserve. The rates shown for a BECU HELOC are based on the prime rate as of the last day of the prior month. This means the rate can change over time based on the prime rate.