kVA ↔ Amps Calculator | Purely Energy

kVA ↔ Amps Calculator

Convert between apparent power (kVA) and current (Amps) for single- or three-phase systems. Ideal for checking supply capacity, main fuse sizing, and LV/HV upgrades.

Voltage presets: UK · Europe · USA
Choose what you want to find.
Most homes are single-phase; many commercial sites are three-phase.
Sets typical L-N and L-L values; you can still edit voltage manually.
Three-phase often uses L-L; single-phase often uses L-N.
1.00
PF reflects how efficiently power is used (typical 0.85–1.00).
Enter values to calculate
Formula used
Single-phase (kVA → A): I = (S × 1000) / (V × PF)
What this is for

Estimate current draw or apparent power to sanity-check supply size (kVA), main fuse ratings (A), and whether upgrades (e.g., moving from 60 A to 100 A, or LV to HV) might be needed. Always consult a qualified electrician/engineer before making changes to your installation.

Assumptions: balanced load on three-phase; sinusoidal waveforms; voltage at point of use. Results are estimates and may differ from site measurements.

kVA to Amps: the quick guide for UK businesses

Choosing the right supply size, main fuse, or generator isn’t guesswork.


Converting kVA (apparent power) to amps (current) helps you check whether your existing electrical capacity is adequate for new equipment, EV chargers, heat pumps, or a solar/battery setup.


UK context: Most premises run at Low Voltage (LV). That’s 230 V single-phase (line-to-neutral) or 400/415 V three-phase (line-to-line). “High Voltage” in the UK starts at ≥ 1 kV and isn’t used directly by standard building services.


What are kVA and amps?

  • Amps (A): how much electrical current is flowing. It’s what your main fuse and many protective devices are rated in.
  • kVA: “apparent power.” It’s the product of voltage and current before allowing for power factor (how efficiently power is converted into useful work). Generators, UPS and transformers are often sized in kVA.

Both matter: amps protect your cables and switchgear; kVA helps size supplies and generation.


How to convert kVA → amps (UK voltages)

Include power factor (PF) if you know it (typical business loads: 0.85–1.00). If unknown, use PF = 1.00 as a quick estimate.

Single-phase (230 V L-N)


Tip: For UK three-phase boards, we typically reference 400/415 V L-L. Your calculator lets you switch between L-L and L-N.


Why this conversion matters for UK sites


1) Equipment compatibility & upgrades
Match new loads (kitchen/catering kit, compressors, servers, EV chargers, heat pumps) to your existing main fuse (A) and service head. If the amps exceed your headroom, you may need a fuse upgrade (e.g., 60 A → 80/100 A) or three-phase.


2) Generator, UPS & solar/battery sizing
Suppliers quote kVA. Your board cares about amps. Converting ensures the generator/UPS can carry starting currents and steady loads. With solar + batteries, kVA↔A helps check inverter output against your circuits.


3) Efficiency & cost control
Poor PF (e.g., 0.8–0.9) raises current for the same kVA, increasing losses and sometimes network charges. Power-factor correction can reduce amps and free capacity.


4) Safety & compliance
Keeping current within cable and protective-device ratings supports compliance with UK wiring rules (e.g., BS 7671) and reduces overheating risk.

Quick UK reference (rule-of-thumb, PF = 1)


Single-phase 230 V:

  • 60 A ≈ 13.8 kVA
  • 80 A ≈ 18.4 kVA
  • 100 A ≈ 23.0 kVA


Three-phase 400 V L-L:

  • 32 A/phase ≈ 22 kVA
  • 63 A/phase ≈ 43–45 kVA
  • 100 A/phase ≈ 69 kVA
Actual available capacity depends on PF, diversity, cable lengths, voltage drop, and how loads start (motors, compressors, HVAC). Treat these as estimates.


Need a hand?

If you’d like us to sanity-check your figures or advise on fuse upgrades, three-phase conversions, generators/UPS, or solar + battery for your site, Purely Energy can help.

No. 230/400–415 V is Low Voltage (LV). High Voltage (HV) starts at ≥ 1 kV (e.g., 6.6 kV, 11 kV).

Small sites are often single-phase 230 V. Larger commercial/industrial sites commonly use three-phase 400/415 V. Check your service head or ask your DNO/installer.

If unknown, use 1.00 for a quick check. Many business sites are 0.85–0.95. Lower PF means higher amps for the same kVA.

No. It’s a planning tool. Always have a qualified electrician/engineer confirm cable sizing, protective devices, discrimination, and thermal limits.