S.C. Code Ann. § 11-15-460: Interest rate.

These refunding bonds must bear interest at those rates as may be determined by the governing body of the issuer. However, before the issuance of any refunding bonds, except in the case of the refunding of Qualified School Construction Bonds issued pursuant to the provisions of 26 U.S.C. Section 54F, the governing body shall determine that a savings can be effected through the issuance of these refunding bonds.