Connected load, MD, demand, diversity, load factor

These terms describe how much of the installed equipment is actually used and when. One example workshop is used for all of them.

Example workshop: 5 motors of 10 kW, lighting 5 kW and heaters 15 kW.

i) Connected load

The sum of the rated (nameplate) powers of all equipment connected to the supply.

Connected load = 5×10 + 5 + 15 = 70 kW

ii) Maximum demand

The greatest load drawn at any time in a period (usually the highest 15- or 30-minute average, read by an MD meter). Not all equipment runs at full load at once, so MD < connected load.

Recorded maximum demand = 42 kW

iii) Demand factor

The ratio of maximum demand to connected load (always ≤ 1).

Demand factor = MD / Connected load = 42/70 = 0.6

It is used to find the MD of a new installation from its connected load.

iv) Diversity factor

The ratio of the sum of individual maximum demands of parts of a system to the maximum demand of the whole system (always ≥ 1).

If the workshop and two other workshops have individual MDs of 42 kW, 30 kW and 28 kW, and the feeder's recorded MD is 80 kW:

Diversity factor = (42 + 30 + 28) / 80 = 100/80 = 1.25

A high diversity factor means smaller transformers and feeders can supply many loads that peak at different times.

v) Load factor

The ratio of average load to maximum demand over a period.

If the workshop uses 504 kWh in a day:

Average load = 504 / 24 = 21 kW
Load factor  = 21 / 42  = 0.5

A high load factor means the plant capacity is used well and the cost per kWh is lower.