Watts to VA Calculator

Small commercial supplies (retail units, single-site SMEs, branch offices) live in the volt-amp world for inverters, UPS units and lighting circuits. A 1000VA UPS does not give 1000W of real power output. At a power factor of 0.7, the same unit delivers around 700W, which is the figure that matters when the till system, the router, the CCTV and the alarm panel all need to ride through a brownout. Reading the nameplate as VA without converting back to watts is how owners end up with kit that fails when it matters.

For lighting and IT loads, the watts to VA conversion is also the basis of cable and breaker sizing on the final circuit. A 5kW lighting load at a power factor of 0.95 draws 22.9A at 230V single-phase. Specify the cable on watts alone and the design is technically out of spec under BS 7671. SMEs adding LED lighting, expanding IT racks, or installing small EV charge points need this conversion to make sure the local design engineer signs off the work cleanly the first time.

Purely Energy works with SMEs from £5k a year of energy spend upwards. We handle the supply contract, advise on capacity changes when the business grows, and connect clients with vetted electrical contractors when they need on-site design work. Our quick-quote flow gets a comparable rate from a panel of 30+ suppliers in under three minutes, and our account team handles the renewals so the owner-operator does not have to track contract end dates across a panel of brokers.