I have provided a lot of testimony in legal proceedings. In making arguments I would have to write a report that would be submitted to all parties in the case. Then, other parties would respond to my arguments and ultimately I would be cross examined by lawyers. I have written testimony on the cost of capital for utility companies, the allocation of costs used as a basis for determining prices; the appropriate structure of prices for residential (domestic) consumers and industrial consumers; demand forecasting for utilities in the context of price cap regulation; geographic cost of service; structuring independent power; M&A approvals and other issues. The testimony is old, but if you are working on some of these subjects, it may give you some ideas.
Cost of Capital for Utility Companies
Rate Design and Cost of Service in Electricity
https://edbodmer.com/wp-content/uploads/2020/07/CostofService-StreetLightsandCustomerCosts2009.pdf