In short. A load list is the foundation of every sizing decision. It records each load’s rating, voltage, efficiency, power factor, duty, starting method and criticality, and from it come the generator, transformer, UPS and cable sizes. Built well, it makes every later number defensible. Built badly, with shaft kW treated as electrical kVA or standby units counted as running, every downstream number inherits the error.
Who this page is for: For electrical contractors, consultants and facility engineers preparing the load schedule for a generator, transformer or UPS.
Key facts
- Motor input kW = shaft kW ÷ efficiency; input kVA = input kW ÷ power factor.
- kVAr = √(kVA² − kW²).
- Total kVA = √((Σ kW)² + (Σ kVAr)²) is more accurate than adding kVA directly.
- Mark each value as measured, nameplate or estimated.
- Connected load is the sum of ratings; running load is what runs together.
- Record duty and criticality so the list drives diversity and load shedding.
Recommended columns
| Column | Why it matters |
|---|---|
| Load name and tag | Traceability |
| Voltage and phases | Distribution and balance |
| Rated kW (shaft or output) | Starting point |
| Efficiency and power factor | Convert to electrical input |
| Input kW, kVA, kVAr | Sizing inputs |
| Duty: continuous, intermittent, standby | Diversity |
| Starting method and current | Generator dip and step plan |
| Criticality class | UPS, generator and shedding decisions |
| Source of the value | Confidence in the result |
Worked example: three loads, two ways to total (illustrative)
| Load | Rated | Efficiency, PF | Input kW | kVA | kVAr |
|---|---|---|---|---|---|
| Motor | 30 kW shaft | 0.92, 0.86 | 32.6 | 37.9 | 19.3 |
| Lighting and small power | 20 kW | –, 0.95 | 20.0 | 21.1 | 6.6 |
| Heater | 15 kW | –, 1.0 | 15.0 | 15.0 | 0 |
| Total | 67.6 | Adding kVA: 74.0; vector sum: about 72.4 | 25.9 |
The vector sum, √(67.6² + 25.9²) ≈ 72.4 kVA at an overall power factor of about 0.93, is the accurate figure; adding kVA directly gives 74.0, slightly conservative. Treating the motor’s 30 kW shaft rating as 30 kVA of electrical load would have understated it by almost 8 kVA. See kVA and kW sizing.
Do not size from a list of nameplate kW. Convert motors to electrical input, mark standby equipment, record starting methods, and state which values are measured and which are estimated.
Where the numbers come from
| Source | Confidence |
|---|---|
| Measured with a power analyser over a typical period | Best |
| Maker’s data for specified equipment | Good |
| Nameplate | Upper bound; often above actual load |
| Estimate | Flag it and review later |
Connected versus running load
Connected load adds every rating. Running load is what actually draws power together, after duty cycles, standby units and diversity. Generators and transformers are sized on running demand plus growth, with the largest motor start checked separately. See maximum demand and diversity and connected load and maximum demand.
Load list template
| Tag | kW | Eff. | PF | kVA | Duty | Start method | Class | Source |
|---|---|---|---|---|---|---|---|---|
Common mistakes
- Shaft kW used as electrical input.
- Standby units counted as running.
- No starting method recorded.
- Estimates not marked.
What to send us
Send your load list or equipment schedule, even if incomplete, and mark what is measured. WhatsApp 98852 01608 or use the enquiry form.
Evidence note. Efficiencies and power factors in the example are typical values for illustration.
Questions engineers ask
What is the difference between kW and kVA?
kW is real power doing work. kVA is apparent power, the product of voltage and current. They are related by power factor.
Why does power factor matter for sizing?
It changes the kVA the generator or transformer must supply for the same kW.
Should I use nameplate or measured values?
Measured where possible; nameplate gives an upper bound and often overstates actual load.
How do I treat standby equipment?
List it but mark its duty so it is excluded from running load, and include it where it may run during a changeover.
Figures are illustrative. Check the numbers against your own equipment data.
Technical content reviewed by D. Srinivas Reddy, Managing Partner and Service Engineer, Reddy Generators. Last updated 8 November 2026.