Free electrical load calculation tool for residential and commercial buildings. Calculate service entrance sizing, panel loads, demand factors, and ensure NEC Article 220 compliance. Primary distribution systems consist of feeders that deliver power from distribution substations to distribution transformers. At this. Peak Load: The maximum load consumed or produced by a group of units in a stated period of time. Maximum Demand: The greatest of all demands that have occurred during a specified period of time. The best distribution system is one that will, cost-effectively and safely, supply adequate electric service to both present and future probable loads—this section is intended to aid in selecting, designing and installing such a system. It accounts for all connected devices, their usage patterns, and safety margins to design circuits, transformers, and distribution panels that operate safely under peak loads. It generally consists of f the.