Formula & Calculator
Demand Factor
Compares the actual maximum demand of a system to its total connected load.
Interpretation
Demand factor = maximum demand / total connected load.
It reflects the fraction of the installed equipment that is actually in use at peak time.
Example: maximum demand = 500kW, connected load = 800kW → DF = 500/800 = 0.625.
Variables
| Symbol | Quantity | Unit |
|---|---|---|
| DF | Demand factor | dimensionless |
| Maximum Demand | Maximum demand (peak load) | W (or VA) |
| Total Connected Load | Total connected load | W (or VA) |
What it means
The demand factor is the ratio of the maximum demand of a system to the total connected load: DF = Maximum Demand / Total Connected Load. It indicates how much of the installed equipment is actually operating at the time of peak demand. A low demand factor suggests that much of the equipment is rarely used. This factor helps in sizing transformers and switchgear. Example: A building has a total connected load of 800kW, but the maximum demand is 500kW. The demand factor is 500/800 = 0.625. This means only about 62.5% of the connected load is simultaneously active at peak times. Understanding the demand factor is important for designing electrical distribution systems to avoid overcapacity.
Worked example
Demand Factor – Practical Example
Real‑World| Parameter | Value |
|---|---|
| Maximum demand | 300 kW |
| Connected load | 500 kW |
| Formula | DF = Maximum Demand / Connected Load |
Common mistakes
Watch for unit mismatches (W vs kW, single- vs three-phase) and remember to include power factor or efficiency where the formula requires it.Applications
Demand factor DF = Maximum Demand / Total Connected Load reflects the fraction of installed equipment that is actually in use at peak time. This is used to size feeders, transformers, and switchgear. Engineers use it to avoid over‑sizing and to reduce capital costs. Understanding demand factor is crucial for designing cost‑effective electrical installations.
- Electrical installation design and sizing
- Transformer and switchgear selection
- Distribution system planning
- Load analysis and capacity studies
- Educational understanding of demand diversity
Frequently Asked Questions
The demand factor is the ratio of the maximum demand to the total connected load: DF = Maximum Demand / Total Connected Load.
It indicates that not all connected equipment is operating at the same time, which is typical in many installations.
Residential: 0.5‑0.7; Commercial: 0.6‑0.8; Industrial: 0.7‑0.9. These are approximations and vary.
It is used to size transformers, feeders, and service equipment, by multiplying the connected load by the demand factor to estimate the maximum demand.
Common errors: 1) using the wrong value for maximum demand, 2) applying it to the wrong load category, 3) not considering future growth, 4) using the factor incorrectly in calculations.
It can be measured over a billing period, or estimated using load survey and coincidence factors.
Demand factor compares maximum demand to connected load; load factor compares average load to maximum demand.
Sizing electrical infrastructure, determining service capacity, and rate negotiations.