How to Calculate the Electrical Demand of a Building: A Consultant's Guide

The calculation of a building’s electrical demand is arguably the most critical step in the entire electrical design process. It is the foundation upon which safety, reliability, efficiency, and project budget are built. Errors in this calculation—whether an overestimation leading to unnecessary capital cost, or, far worse, an underestimation resulting in overloaded infrastructure and potential fire hazards—can have severe and long-lasting consequences for owners, occupants, and the consulting firm responsible.
This book, "How to Calculate the Electrical Demand of a Building: A Consultant's Guide," is designed to bridge the gap between theoretical code requirements and the practical, nuanced demands of real-world consulting. It goes beyond simply quoting tables from the National Electrical Code (NEC) or other international standards. Instead, it offers a systematic, consultant-level methodology honed over decades of international practice across diverse facility types—from complex industrial plants to high-density commercial towers.
We will explore not only the mandated calculations for lighting, receptacles, and motor loads, but also the strategic application of professional judgment, including the art and science of justifying Diversity Factors and navigating the crucial process of utility coordination. Our goal is to equip you with the knowledge to perform accurate, defensible, and optimized demand calculations that ensure regulatory compliance while delivering maximum value to your client. This guide is a mandatory resource for moving from merely being a designer to becoming a truly effective and respected electrical consultant.