Transformer Fundamentals
Load Factor and Transformer Demand
Use it to understand how steadily a site uses power and to organize the demand profile for a transformer review.
Electrical load factor compares average demand with the maximum demand during the same period. It describes how steadily a site uses power and helps organize the demand profile for a transformer review.
Use one measurement period
Load factor = energy in kWh / (peak demand in kW × hours in the period). Read energy and demand from the same meter boundary and billing interval. Identify the demand averaging interval as well as the calendar period.
Load factor formula
Load factor = average demand / peak demand
Average demand = energy use / hours in the period. Keep energy, peak demand and elapsed hours on the same time and meter basis.
Work through a monthly example
A site uses 120,000 kWh in a 30-day period of 720 hours and records a 300 kW peak. Average demand is 166.7 kW and load factor is 55.6%. If the same energy is delivered with a 250 kW peak, load factor becomes 66.7%. This comparison illustrates load smoothing.
| Item or condition | What to compare | Input or result |
|---|---|---|
| Energy and period | 120,000 kWh / 720 h | 166.7 kW average |
| Measured peak | 300 kW | 55.6% load factor |
| Illustrative smoother profile | 250 kW peak, same energy | 66.7% load factor |
The calculated average uses 120,000 kWh / 720 h = 166.7 kW. Dividing by the recorded 300 kW peak gives 55.6%; with a 250 kW peak, it gives 66.7%.
Connect the profile to equipment duty
Keep peak kW, power factor, motor starting, operating hours and planned expansion in the capacity review. A load-factor value describes utilization over time; peak and transient conditions remain separate inputs to the transformer specification.
Frequently Asked Questions
How does load factor differ from power factor?
Load factor compares average and peak demand over time. Power factor compares active and apparent power under the stated operating conditions.
Which records should accompany the calculation?
Provide the energy period, demand interval, peak demand record and a representative load profile.
Prepare your transformer demand profile
Share the energy period, peak demand interval, load profile, power factor, starting conditions and planned expansion when reviewing transformer duty.