500VA equals how many volt-amperes equals how many watts

500V/A is 500 volt-amperes, and the relationship between volt-amperes and watts is. Watt = Volt-Ampere * Power Factor Say your device is connected to a power supply with a power factor of 0.8, then the wattage is 500*0.8=400, and in reality your device is only doing 400W of power. But the power company is charging you for 500W!