Environmental Compliance Cost Transparency Act of 2018 This bill requires the Bonneville Power Administration, the Western Area Power Administration, the Southwestern Power Administration, and the Southeastern Power Administration to include in monthly billing statements sent to each customer estimates of the customer's share of such administration's direct and indirect costs for compliance with any relevant federal environmental laws impacting the conservation of fish and wildlife. Each administration must report each year on: (1) estimated costs and factors affecting total power costs, including total direct and indirect compliance costs; and (2) sources of replacement power.