Load factor

Load factor may refer to:

Load factor (electrical)

In electrical engineering the load factor is defined as the average load divided by the peak load in a specified time period.

Typical example of a large commercial electrical bill: kW Demand = 436 kW; kWh Use = 57,200 kWh; Number of days in billing cycle = 30d

Load Factor [%] = {(57,200 kWh / (30 days X 24 hours per day X 436 kW)} X 100% = 18.22%

It can be derived from the load profile of the specific device or system of devices. Its value is always less than one because maximum demand is always higher than average demand, since facilities likely never operate at full capacity for the duration of an entire 24 hour day. A high load factor means power usage is relatively constant. Low load factor shows that occasionally a high demand is set. To service that peak, capacity is sitting idle for long periods, thereby imposing higher costs on the system. Electrical rates are designed so that customers with high load factor are charged less overall per kWh. This process along with others is called load balancing or peak shaving.

Load factor (aeronautics)

In aeronautics, the load factor is defined as the ratio of the lift of an aircraft to its weight and represents a global measure of the stress ("load") to which the structure of the aircraft is subjected:

where:

Since the load factor is the ratio of two forces, it is dimensionless. However, its units are traditionally referred to as g, because of the relation between load factor and apparent acceleration of gravity felt on board the aircraft. A load factor of one, or 1 g, represents conditions in straight and level flight, where the lift is equal to the weight. Load factors greater or less than one (or even negative) are the result of maneuvers or wind gusts.

Load factor and g

The fact that the load factor is commonly expressed in g units does not mean that it is dimensionally the same as the acceleration of gravity, also indicated with g. The load factor is strictly non-dimensional.

The use of g units refers to the fact that an observer on board an aircraft will experience an apparent acceleration of gravity (i.e. relative to his frame of reference) equal to load factor times the acceleration of gravity. For example, an observer on board an aircraft performing a turn with a load factor of 2 (i.e. a 2 g turn) will see objects falling to the floor at twice the normal acceleration of gravity.