N.H. Rev. Stat. § 365:38
Whenever any investigation or proceeding shall be necessary to enable the commission to pass upon the reasonableness of the rates or charges by a public utility, the utility shall pay to the department of energy the expenses involved in the investigation, including the amounts expended by the commission and the department of energy for attorneys, experts, accountants, or other assistants, but not including any part of the salaries or expenses of the commissioners or of employees of the commission or department of energy; provided, that the amount charged to the utility in any such case shall not exceed 3/4 of one percent of the existing valuation of the utility investigated, such expenses with 6 percent interest to be charged by the utility to operating expenses and amortized over such period as the commission shall deem proper and allowed for in the rates to be charged by the utility.
RSA 365:38
1921, 138:1. PL 238 :36. 1931, 127:1. RL 287:37. 1951, 203:11 par. 38. RSA 365:38. 1959, 242:4, eff. Oct. 20, 1959. 2021, 91:252, eff. July 1, 2021.