How to calculate the right voltage stabilizer size
Choosing by appliance name or breaker amps alone can produce the wrong result. This guide connects watts, kW, kVA, amps, power factor, phase, starting current and input range so you can prepare an accurate Rustek request.
Use the kVA calculator →For a basic load, apparent power is approximately kVA = kW ÷ power factor. For current-based checks, single-phase kVA = V × A ÷ 1000, while balanced three-phase kVA = √3 × line-to-line V × A ÷ 1000. Final selection must also cover startup, input range, ambient conditions and manufacturer-rated capacity.
kW, kVA and amps answer different questions
| Term | Meaning | Use in stabilizer selection |
|---|---|---|
| W / kW | Real power used by the load | Build the connected and simultaneous load list |
| VA / kVA | Apparent power handled by the electrical equipment | Primary stabilizer capacity rating |
| Power factor | Relationship between real and apparent power | Convert kW demand to kVA correctly |
| Amps | Current at a stated voltage and phase | Verify conductors, breakers and stabilizer current |
| Input range | Voltage window in which the AVR regulates | Match the actual site condition |
Estimate apparent power from voltage and current
This is a base electrical calculation, not a final product recommendation. Use line-to-line voltage for the balanced three-phase option.
Estimated base kVA
Does not include starting current, margin, derating, low-input current effects or load imbalance.
From appliance list to model shortlist
Define protected loads
Choose one appliance, selected circuits, the whole home, miners or an industrial load group.
Calculate simultaneous demand
Add loads likely to operate together rather than blindly totaling every nameplate.
Identify dynamic loads
Record motor, compressor, transformer and PSU startup or overload behavior.
Convert and verify
Convert real load to kVA using appropriate power factor, then verify current and phase.
Match the input range
Confirm the AVR can regulate at the measured minimum and maximum voltage under load.
Add justified margin
Allow for actual operating conditions and planned growth without arbitrary oversizing.
What causes an inaccurate recommendation
Information to send Rustek
| Load list | Model, watts, amps and operating mode |
| Voltage | Minimum, maximum and nominal supply |
| Phase | Single or three phase and line voltage |
| Installation | Indoor/outdoor, ventilation and connection |
| Growth | Specific equipment planned for the future |
Answers without oversimplifying
Yes, when voltage and phase are known. Use V × A ÷ 1000 for single phase or √3 × line voltage × A ÷ 1000 for a balanced three-phase load.
There is no universal percentage for every load. Margin should reflect startup, input range, temperature, duty, expansion and the specific product’s rating method.
No. They are equal only at unity power factor. For example, apparent power increases as power factor falls for the same real-power demand.
Choose your application
Want Rustek to check the calculation?
Send your load list, voltage range and phase before you choose a model.