Create customer profiles for your connections, generate invoices from meter readings on a billing cycle, and record the money in the built-in double-entry accounting module. It is one system rather than a register in one place and books in another.
Video: Customer Management Feature Launch Webinar on YouTube
Small utilities commonly keep the customer register in one spreadsheet, meter readings in a second and the accounts in a third, so nobody can say what a given connection owes without reconciling three files by hand. Bringing them together is what makes monthly reporting possible at all, and it is what a regulator or a lender will expect to see.