Factory Load Calculator — kW, kVA & 3-Phase Line Amps (380–480 V)
Screen plant kW from device count × kW per device, then balanced three-phase line A and kVA at line V and PF—use Quick Examples for presets. THD, phase unbalance, and fault levels are not modeled; diversity and code-final protection still need field data and engineer sign-off.
Input Parameters
Quick: device count and kW per device. Advanced: voltage and PF selects refine the screening estimate.
Quick Examples:
About this calculator
Rolls up device counts, average kW, PF, and site voltage into a first-pass plant kW/kVA picture before detailed load schedules. For the broader kW→kVA→current chain, use the power calculators hub. For annual kWh and cost screening from kW, see the Industrial Energy Estimator.
After screening kW here, continue with kW to kVA then kVA to amps. With line current in hand, pre-check breaker sizing, cable ampacity, voltage drop, and generator sizing; use 3-phase power when you already know line A and need kW/kVA checks.
Calculation Results
Calculation Results
Apparent Power: 5.88 kVA
Total Current: 8.49 A
Recommended Breaker: 20 A (1.25× on continuous I — screening hint only)
Equipment Recommendations
Circuit Breaker: 20 A (standard size: Yes)
Cable Size: 2.5-4 mm² (14-12 AWG) (order-of-magnitude only; apply installation method and temperature derating per your adopted code—not a substitute for ampacity tables)
Transformer Size: 50 kVA (screening step only; validate kVA with load profile and engineer)
Downstream checks
Breaker size · Cable ampacity · Voltage drop · Generator sizing
Note: This is a simplified calculation. Actual requirements depend on diversity factors, demand factors, starting currents, and local electrical codes. Always consult a licensed electrical engineer for final design.
Default example: 5 devices × 1 kW at 400 V L-L, PF 0.85 (balanced three-phase, simultaneous-use). Reduce counts or kW per device to mimic diversity before locking mains. After you adjust inputs, results update in place. Continue to kW to kVA, then kVA to amps; validate protection with breaker, cable, and voltage drop tools.
Engineering disclaimer
This calculator provides preliminary load estimates only. For final electrical system design, installation, and compliance with local electrical codes (NEC, IEC, etc.), consult a licensed electrical engineer or certified professional. Actual requirements may vary based on detailed load calculations, diversity factors, demand factors, and specific application requirements.
Equipment load planning reference
Use nameplate data when available. Ranges below are for early budgeting only—measure demand during peak shifts for real diversity.
| Equipment class | Typical unit kW | Planning diversity note |
|---|---|---|
| Small CNC / bench tools | 2–15 kW | Not all machines cut at once—use line-level metering if multiple spindles. |
| Injection molding / presses | 20–200 kW | Cycle duty lowers average demand; capture peak kW during heat/boost. |
| HVAC rooftop / chiller plant | 50–800+ kW | Cooling peaks differ from production peaks; model seasonally. |
| LED high-bay lighting | 0.1–0.3 kW/fixture | PF near unity; group circuits for panel balancing. |
| Compressed air (fixed speed) | 30–300 kW | Multiple compressors may share load—avoid double counting standby units. |
Factory Load Formula & Explanation
Screening real power: kW = device count × kW per device. Balanced three-phase line current: I = (kW × 1000) ÷ (√3 × V × PF). A 1.25× multiplier on I is a planning hint only—confirm Articles 240/430, feeders, and transformer kVA with adopted NEC / IEC 60364 and a licensed engineer. Do not map dwelling receptacle-demand tables (for example NEC 220.42) onto industrial plant buswork without jurisdiction-specific review.
- I
- Balanced three-phase line current (A RMS) per conductor.
- V
- System line-to-line RMS voltage (V).
- PF
- Displacement power factor (cos phi); harmonics not modeled.
- kW
- Real (active) power from the simultaneous-use device model.
- kVA
- Apparent power, kW ÷ PF for sinusoidal assumption.
kW vs kVA: this tool stays at kW plus PF; continue with kW to kVA then kVA to amps for the current leg at your V and phase.
Example: 5 devices × 1 kW, 400 V L-L, PF 0.85 → 5 kW; I ≈ 8.49 A; screening overcurrent hint rounds toward a standard device after 1.25× on continuous current.
- Simultaneous model: lower counts or kW to reflect your duty cycle and diversity.
- V: line-to-line; PF: nameplate or metered when possible.
- Breaker hint: not selective coordination or cable ampacity by itself.
- Not modeled: harmonic distortion (THD), phase unbalance, available fault current, or selective coordination—use field studies and adopted code tables.
More: Factory load guide · 3-phase power · kW to kVA · kVA to amps (single-phase) · Breaker size · Cable size · Voltage drop · Generator sizing · Transformer sizing · Energy estimator · Power Calculators Hub
kVA² = kW² + kVAR²; with PF known, PF = kW ÷ kVA.
Factory scale planning examples (three-phase)
Illustrative demand kW after a diversity factor on connected kW; line A uses balanced three-phase kW at 400 V and PF 0.85—tune counts in the calculator for your site.
| Scenario | Connected kW (sum) | Assumed diversity | Demand kW | Approx. line A |
|---|---|---|---|---|
| Job shop (1 shift) | 320 | 0.75 | 240 | ~408 A |
| Food processing (cold + washdown) | 900 | 0.70 | 630 | ~1,070 A |
| Warehouse + DC chargers | 600 | 0.65 | 390 | ~662 A |
Current uses demand kW with √3, V, and PF; add harmonics, spare capacity, and code factors before selecting mains protection.
Frequently Asked Questions
How accurate is the factory load calculator?
It applies textbook balanced three-phase relationships to your inputs. Real plants differ due to diversity, harmonics, unbalance, and duty cycles. Treat outputs as screening only and verify critical designs with metering and a licensed engineer.
What does the 1.25× screening hint mean for breakers?
The tool multiplies estimated continuous line current by 1.25 as a rough planning margin for inrush and growth. It is not a substitute for NEC Article 240/430 or IEC 60364 device selection, coordination, or cable ampacity tables—always confirm with code and qualified engineering.
Can I use this calculator for single-phase systems?
It is optimized for balanced three-phase. For single-phase, omit the √3 divisor in the current formula, or continue with kVA to Amps (Single-Phase) when you already have kVA and line-to-neutral voltage.
What power factor should I use if I don't know the exact value?
Use 0.85 as a conservative default for mixed industrial loads; motors are often 0.8–0.9 and resistive loads approach 1.0. Prefer nameplate or metered PF when available.
Does the calculator account for load diversity?
By default it assumes simultaneous operation. Reduce device counts or kW per device to reflect diversity, or apply a demand factor offline before comparing to utility or transformer limits.
How do I convert factory kW to three-phase line amps?
For balanced three-phase: Amps = (kW × 1000) ÷ (√3 × line-to-line voltage × power factor). This page uses that relationship; for single-phase line-to-neutral loads, remove the √3 term.