Demand factor in a commercial load calculation is the ratio of a load’s actual maximum demand to its total connected load, used to account for the fact that not all loads in a building run at full capacity at the same time. Because applying the full connected load would oversize the system, code allows demand factors to reduce certain loads to a realistic level for sizing. Understanding demand factor helps explain why a building’s service can be smaller than the sum of everything plugged into it.

Here is what demand factor is in commercial load calculation.

Demand factors are defined by code for specific load types and occupancies, so their application is determined by qualified electricians or engineers following the applicable code.

The ratio of demand to connected load

Demand factor is defined as the ratio of the maximum demand of a system (or part of it) to its total connected load. In other words, it compares how much load is actually expected to be drawing at peak to the total of all the loads connected. A demand factor less than 100 percent means the actual peak demand is expected to be less than the full connected load, which is usually the case.

Why demand factors exist

Demand factors exist because, in most buildings, not all loads operate at full capacity simultaneously. For example, not every receptacle is loaded to maximum at once, and many loads vary. If a system were sized for the full connected load, assuming everything runs at maximum together, it would be oversized and wasteful. Demand factors capture realistic simultaneous usage, allowing the system to be sized for the actual expected demand rather than an unrealistic worst case.

How they are applied

In a load calculation, code-defined demand factors are applied to the applicable loads to reduce them from their connected value to a calculated demand value. The code specifies the demand factors for particular load types and occupancies, for example allowing certain loads to be counted at reduced percentages according to defined schedules. Applying the correct demand factors to the right loads is part of performing the load calculation properly, which is why it follows the code’s rules.

Not all loads get a demand factor

An important point is that not every load is reduced by a demand factor. Some loads are counted at full value, and continuous loads are actually increased (counted at 125 percent). Demand factors apply where the code permits them, based on the load type and occupancy, reflecting realistic usage for those loads. So the calculation is a mix: some loads reduced by demand factors, some at full value, and continuous loads increased, all per the code.

Its role in sizing

Demand factor plays a key role in right-sizing a commercial electrical system. By reducing applicable loads to their realistic demand, it helps arrive at a calculated load that reflects actual expected usage, so the service and equipment are sized appropriately, neither wastefully oversized nor dangerously undersized. Because applying demand factors correctly requires knowing the code’s rules, it is handled by qualified professionals as part of the load calculation.

Demand factor in a commercial load calculation is the ratio of a load’s actual maximum demand to its total connected load, used to account for the fact that not all loads run at full capacity at once. Code allows demand factors to reduce applicable loads to a realistic level for sizing, preventing wasteful oversizing. Not all loads get one, continuous loads are instead increased, and applying the correct factors per code is part of a proper load calculation done by professionals.

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