The difference between connected load and demand load is that connected load is the total of all the electrical loads installed in a building added together, while demand load is the realistic maximum amount actually expected to draw power at the same time, which is usually lower because not everything runs at once. This distinction is central to sizing electrical systems correctly, since sizing for the full connected load would be wasteful. Understanding it helps explain how commercial systems are sized for real-world usage rather than a theoretical maximum.

Here is the difference between connected load and demand load.

Connected load, demand load, and the factors relating them are defined and applied under code, so load calculations are performed by qualified electricians or engineers following the applicable code.

Connected load: the sum of everything

Connected load is the total of all the electrical loads connected in a building, every light, receptacle, appliance, and piece of equipment, added together at their full values. It represents the maximum the building could draw if everything ran at full capacity simultaneously. Connected load is the starting point of a load calculation, but it is a theoretical maximum that rarely, if ever, actually occurs, because not everything is on at once.

Demand load: what actually draws at once

Demand load (or maximum demand) is the realistic maximum amount of power actually expected to be drawn at the same time. Because not all loads operate at full capacity simultaneously, the demand load is typically lower than the connected load. It reflects actual usage patterns, the realistic peak, rather than the theoretical total. Demand load is what the system actually needs to supply at its busiest, which is the meaningful figure for sizing.

How they relate: the demand factor

Connected load and demand load are linked by the demand factor, the ratio of demand load to connected load. Applying demand factors (as permitted by code) to the connected load reduces it to the calculated demand load, accounting for loads that do not all run at once. So the demand load is derived from the connected load by applying these factors. The continuous-load rule also enters the calculation, increasing continuous loads. Together these turn the raw connected load into a realistic demand figure.

Why the difference matters

The difference matters because systems are sized to the demand load, not the full connected load. Sizing to the connected load would mean oversizing the service and equipment for a maximum that never happens, which is wasteful and costly. Sizing to the realistic demand load provides adequate capacity for actual usage with appropriate margins, at a sensible size. This is why load calculations convert connected load into demand load before sizing the system.

A simple way to think about it

A simple way to think about it: connected load is everything you could possibly run at once, while demand load is what you realistically will run at once. A building might have a large connected load on paper, but since not all of it operates simultaneously, the demand load, the figure that matters for sizing, is lower. Qualified professionals calculate the demand load from the connected load using code rules, and size the system accordingly.

Connected load is the sum of all the electrical loads in a building added together, a theoretical maximum, while demand load is the realistic maximum actually expected to draw power at once, usually lower because not everything runs simultaneously. They are linked by the demand factor, and systems are sized to the demand load, not the full connected load, to avoid wasteful oversizing. Qualified professionals calculate demand load from connected load per code and size the system to it.

Stella Electric performs accurate load calculations and sizes commercial systems correctly for businesses across the Baltimore area and throughout Maryland, with flat-rate pricing and no overtime charges. If you need your electrical load assessed, we can help. Financing is available on qualifying projects.