N.H. Rev. Stat. Ann. § 374:18

The commission, by order, or the department of energy, may require any public utility to produce within the state, at such time and place as it may designate, any accounts, records, memoranda, books, or papers kept in any office or place without the state, or verified copies thereof, in order that an examination thereof may be made by or under the direction of the commission or the department of energy.