Electrical Load Schedule: How to Build One
A load schedule is the table behind every sizing decision. If it is wrong, the transformer, generator and cable sizes are wrong with it.
Columns
| Column | Purpose |
|---|---|
| Description, tag and location | Identify the load |
| Rating (kW or kVA), voltage, power factor | Connected load |
| Efficiency | Converts motor output to input power |
| Demand factor | What proportion runs at once |
| Source and path | Utility, generator or UPS; A or B path |
Steps
- List every load, by board, from the equipment schedules.
- Convert each to input power (kW and kVA) at its power factor and efficiency.
- Apply demand factors, justified by how the load behaves.
- Sum by board, then by source and redundancy path.
- Add the margin and growth the design commits to, and say so.
- Use the totals to size equipment. See load calculation, generator sizing and UPS sizing.
Common mistakes
- Mixing kW and kVA in the totals.
- Using demand factors that do not suit continuous loads such as IT and cooling.
- Not splitting by redundancy path, so the failure case is never checked.
- Letting the schedule drift from the single-line diagram.
Written by the Vision Matrix Institute editorial team. Worked examples use stated, illustrative assumptions; check them against your project data, the applicable standards and manufacturer datasheets before use.
Frequently Asked Questions
What is an electrical load schedule?
A table listing each load with its rating, power factor, load or demand factor and power source, summed per board and per source to give the demand each part of the system must serve.
What is the difference between connected and demand load?
Connected load is the sum of ratings. Demand load applies demand or diversity factors for how much will actually run at once.
What columns should it have?
Load description, location, board, quantity, rating, voltage, power factor, efficiency where relevant, demand factor, source (utility, generator or UPS) and redundancy path.
How is it used?
Totals feed the transformer, switchgear, UPS and generator sizing, and the single-line diagram. It is updated as the design changes.
Want to learn this properly?
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