Tenn. Code § 65-167
Any commissioner whose service is terminated for any reason shall, in lieu of all other benefits provided by the public service commissioners' retirement system established by §§ 65-151 - 65-168, be entitled to a refund of his contributions without interest if his service at the time of termination is less than five (5) years, or be entitled to a refund of his contributions accumulated at three per cent (3%) interest, or at another rate of interest as the board of trustees may from time to time declare, if at the time of such termination he has completed at least five (5) years of service. Any commissioner who fails to win reelection or who voluntarily retires or terminates his service before becoming eligible for any of the benefits otherwise provided in the public service commissioners' retirement system may be permitted to allow his contributions to remain until he reaches the age of sixty-five (65) at which time he shall be eligible for a retirement benefit based on his actual service at the time of termination, computed in the same manner as a normal retirement benefit in accordance with the provisions of § 65-152(g). Provided, further, that any commissioner who has completed twelve (12) years at the time of his termination of service and who elects to leave his contributions in the public service commissioners' retirement system may, in lieu of receiving a benefit commencing at age sixty-five (65), elect to receive a benefit starting at an earlier age, but after age fifty-four (54), determined actuarially to have the same value as the benefit that would otherwise commence at age sixty-five (65).
T.C.A. § 65-167