VA to Amps Calculator

VA to amps is the workhorse conversion for anyone specifying UPS, inverter, transformer or generator equipment on a UK commercial site. Manufacturers rate kit in kVA because the apparent power is what determines the copper, the iron and the cooling. Installers, however, need to know the per-phase amps so they can size cables, breakers and protection. A 100 kVA UPS on a 400 V three-phase supply draws 144 amps per phase at unity power factor, and rather more once the protected load is reactive. Specifying the breaker for the kW figure rather than the kVA figure is a regular cause of nuisance trips on day one.

For comms rooms, manufacturing process islands and any site running a static UPS in double-conversion, the VA to amps maths also dictates how much spare capacity the supply panel actually holds. Adding a second UPS module to a panel that looks fine on a kW spreadsheet routinely overloads the upstream MCCB once the kVA is read against amps. The same applies to inverter sizing on solar and battery projects, where the inverter nameplate is in kVA but the AC-side cable and protection has to be designed against amps. Get the conversion wrong and the bill is a re-pull of cable.

Purely Energy sees the downstream consequences of these decisions on the supplier bill. Sites that consistently run a low power factor pay reactive charges and risk an MIC uplift; sites that run their UPS panels close to nameplate amps tend to also be the sites whose maximum demand spikes hit DUoS red bands. Treating the VA to amps conversion as a routine sanity check on every panel diagram tightens the link between the kit nameplates, the supply capacity, and the monthly invoice. The tool above is for the engineering side; the contract conversation is where we add value.