S.C. Code § 5-31-1920
The limitation of two years imposed by Section 5-31-1910 shall not apply to cities having a population of over seventy thousand according to the 1940 United States census, and such cities may enter into a contract as set forth in said section with persons, other cities, towns, public service commissions or political subdivisions without the corporate limits of the city, whether contiguous to the corporate limits or not, either for lighting or manufacturing or any other purposes, for any period or periods not exceeding fifty years, and such contracts may include options for extending the existence thereof beyond the date of their expiration for any additional period or periods, not exceeding fifty years, and for similar extensions beyond the date of any such extended period or periods.
S.C. Code § 5-31-1920