Right-size switchgear and transformer capacity using practical inputs. Includes diversity, power factor, and contingency settings. Compare options, reduce oversizing, and plan upgrades confidently today.
Enter loads in kW. Demand factors reduce connected load to expected operating demand. Margins help cover uncertainty, growth, and spare capacity.
Accurate sizing starts with a structured load schedule. Enter each equipment group with realistic kW values and quantities. Keep motor and HVAC blocks separate so diversity applies correctly. Connected load reflects nameplate totals, while diversified load reflects expected simultaneous operation. Review duty cycles, process sequences, and operating hours. Update the schedule whenever drawings change and procurement clarifies actual ratings during design, and record assumptions in worksheet.
Diversity and power factor drive the kVA outcome. Apply a demand factor per row to reduce loads that rarely coincide, then apply a project demand factor for overall uncertainty. Convert kW to kVA using the selected power factor; lower power factor increases required kVA. If you have measured site data, use it. Otherwise choose conservative values and document assumptions for review, before finalizing the transformer rating.
Margins translate planning decisions into capacity. Contingency covers minor scope changes, growth covers forecast expansion, and spare capacity provides operational headroom. The calculator multiplies these allowances to produce margin adjusted kW, then converts to required kVA. A utilization limit ensures the selected rating is not fully loaded in normal operation, improving thermal performance, efficiency, and future flexibility for the site, for maintenance, harmonics, and seasonal peaks.
Transformer selection should align with standard ratings and reliability goals. The tool selects the smallest standard kVA meeting the utilization adjusted requirement. Full load current is calculated from the selected rating and voltage for single phase or three phase systems. If N plus one is enabled, two units are assumed, each capable of carrying the demand. Confirm impedance and protection coordination with utility requirements and studies.
Outputs support documentation and early procurement decisions. Use the results table to capture connected kW, diversified kW, required kVA, selected rating, and expected loading percentage. Export CSV for design spreadsheets and PDF for submittal packages. Treat the recommended main device as preliminary; final selection must consider fault level, derating, cable sizing, ambient temperature, and local standards. Recalculate after major scope revisions and document deviations for approval.
It estimates transformer kVA and indicative main device amperes from diversified kW, power factor, and margin settings. It also selects the nearest higher standard rating and reports expected loading.
Use operating knowledge: continuous loads near 1.0, intermittent groups lower, and mutually exclusive processes even lower. When uncertain, start conservative and refine with measured data or agreed design criteria.
Enter the nominal bus voltage used for current calculation at the point you are sizing protection. For MV substations, use the MV side. For LV switchboards, use the LV secondary voltage.
Running below 100% rating improves thermal performance and leaves room for future loads. Many designers target 70–85% normal loading, but utility and project standards may differ.
When enabled, the tool assumes two transformers and sizes each unit to carry the full required demand alone. It does not split the load; it supports a simple redundancy concept for early planning.
No. It is a preliminary selection based on 125% of calculated full-load current and standard steps. Final devices must consider fault level, coordination studies, derating, and cable or bus limits.
Important Note: All the Calculators listed in this site are for educational purpose only and we do not guarentee the accuracy of results. Please do consult with other sources as well.