N.H. Rev. Stat. Ann. § 374-C:9

To the extent that other securities of a public utility are legal investments under state law, the state and all public officers, and agencies thereof, public utilities, all banks, trust companies, savings banks and institutions, building and loan associations, savings and loan associations, investment companies, and other persons carrying on a banking business, all insurance companies, insurance associations and other persons carrying on an insurance business, and all executors, administrators, guardians, trustees and other fiduciaries may legally invest any sinking funds, moneys or other funds belonging to them or within their control in any bonds or notes issued pursuant to this chapter, and such bonds or notes shall be authorized security for any and all public deposits.