Maximum Demand and Diversity Explained

Maximum demand is the greatest load an installation (or circuit) is likely to draw at any one time. Diversity is the recognition that not every load operates simultaneously at full power — so the design demand can sensibly be less than the sum of all connected loads.

Why it matters

Sizing supplies, cables and protective devices to the realistic maximum demand — rather than the theoretical total — allows installations to be designed economically without compromising safety. Getting it wrong in either direction causes problems: overestimate and the installation is needlessly expensive; underestimate and circuits become overloaded.

Where it appears

• New installations and alterations — assessing whether the supply and boards can accommodate additional load (for example new EV chargers or heating).
• Capacity assessments — a key input when adding significant new loads. See electrical capacity assessment for EV charging.

On an EICR

Signs of overload — overheating, undersized conductors, or circuits extended beyond their capacity — are recorded and coded according to risk. Understanding maximum demand and diversity helps duty holders plan additions without overloading the installation.