kVA to Amps Calculator

Most UK commercial sites are quoted incoming supply in kVA, sized in amps per phase, and billed in kWh, and the three numbers have to line up. A 500 kVA supply at 400 V three-phase works out to roughly 722 amps per phase, and that figure sets the upper limit on every cable, breaker, busbar, and submeter downstream of the cut-out. Get the conversion wrong by 10 percent and the difference shows up either as nuisance tripping or as paid-for capacity that the site never uses.

Maximum Import Capacity (MIC) bands are where this gets expensive. A site that creeps above its agreed MIC pays excess capacity charges that can run to several thousand pounds a year on a single MPAN, and the fix is either to lift the MIC (and pay more in standing charges every month) or to actively manage demand to stay under it. Picking the right band depends on understanding the kVA-to-amps relationship for the actual load mix on site, not just the nameplate sum.

Purely Energy works with clients on MIC reviews where a careful audit can drop the agreed capacity by 20 to 30 percent without restricting operations, or alternatively flag where an EV charger rollout or a heat-pump retrofit needs a capacity uplift booked with the DNO well in advance. The half-hourly data tells the truth on actual draw, and the conversion maths here is how that data becomes a defensible procurement decision.