Miss. Code Ann. § 75-17-35

Notwithstanding any provision of law to the contrary, the lawful rate of interest which shall be paid on a refund of excess rates by any public utility which has put rates into effect under bond, as provided for in Sections 77-3-39, 77-3-69 and 77-3-71, shall be computed from the date of collection until the date refunds are made and shall be equal to a rate which is two percent (2%) above the average discount rate for the total period under bond, excluding any surcharge thereon, on ninety-day commercial paper in effect at the Federal Reserve bank in the Federal Reserve district where the public utility has its principal place of business.