Amps to kW Converter
Convert amps to kilowatts for single and three-phase circuits
Reference Info & Formulas
Single Phase
kW = (V × I × PF) / 1000
Three Phase
kW = (√3 × V × I × PF) / 1000
6A: Lighting (1.38 kW)
16A: Immersion (3.68 kW)
20A: Radial (4.60 kW)
32A: Ring final (7.36 kW)
40A: Cooker (9.20 kW)
Data: Standard electrical formulas (P = V × I × PF)
For guidance only. The responsibility for any electrical installation lies with the qualified person carrying out the work. Always verify calculations independently and apply professional judgement.
How This Calculator Works
Converting amps to kilowatts gives the real power consumed by a load, accounting for power factor in AC circuits.
For single-phase circuits, multiply the voltage by the current and power factor to obtain real power in watts. For purely resistive loads, real power and apparent power are equal because the power factor is 1.0. For inductive loads such as motors, the real power is always less than the apparent power (V × I).
P = V × I × PF- P
- = Real power in watts
- V
- = Supply voltage (230V UK single-phase)
- I
- = Current in amps
- PF
- = Power factor (1.0 for resistive loads)
IET Guidance Note 1
For three-phase circuits, the formula becomes P = √3 × V × I × PF, where V is the line-to-line voltage of 400V in the UK.
Quick Reference — Amps to kW at 230V
Common circuit ratings and equivalent power (PF = 1.0)
| Current (A) | Power (kW) | Typical Circuit |
|---|---|---|
| 6 | 1.38 | Lighting circuit |
| 10 | 2.30 | Low-load radial |
| 13 | 2.99 | 13A fused plug maximum |
| 16 | 3.68 | Immersion heater radial |
| 20 | 4.60 | 20A radial circuit |
| 32 | 7.36 | Ring final / cooker circuit |
| 40 | 9.20 | Shower circuit |
| 50 | 11.50 | Large shower / sub-main |
Values assume 230V single-phase and unity power factor. For motor loads, multiply by the actual PF.
Practical Notes
The 13A Socket Limit
Motor Nameplate Ratings
Frequently Asked Questions
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