1. Calculation method of interest: general loan interest is expressed as annual interest rate, which can be calculated according to specific conditions. When the loan principal is repaid every month, part of the repayment amount will be used to pay interest.

2. Average interest rate level: The interest rate level varies by region and credit rating. Generally speaking, the annual interest rate of personal loans is between 5%- 15%.

3. Repayment period: The loan period will also affect the total interest. If it is a one-year term, according to the annual interest rate, the total interest may be between 750 and 2250 (assuming the interest rate is between 5%- 15%).

To sum up, the normal interest range for a loan of one year 15000 is about 750 to 2250. Please note that this is only an estimate, and the actual interest may vary due to various factors. It is recommended to consult banks or financial institutions to obtain exact loan interest rate information.