Neb. Rev. Stat. § 70-1303: Neb. Rev. Stat. § 70-1303

A purchaser of electricity at wholesale shall pay to the supplier of such electricity the entire amount of the charge for such electricity within the time set forth in the power contract between the purchaser and supplier or, if no such contract exists or no time is set forth in the contract, within thirty days after the date on which the supplier mails the billing to the purchaser.