A:Answer True power (Watts) is Volt-Amps times the power factor. The power factor depends on the load. In an AC circuit, inductive (magnetic coil) loads (e. g. motors) or capacitive loads (power supplies) can shift the phase of the current with respect to the voltage (i. e., one is delayed in time compared to the other). This is measured by a phase angle, so if the current is delayed by 1/8th of a cycle, the angle is 45° (360°/8). The power factor is the cosine of the phase angle, which in our example is about 0.7071. The power a 650 VA UPS can deliver to this particular load is 650 * 0.7071 = 460 Watts.
Many newer Energy Star rated electronic products have built-in power factor correction, so they will have a power factor close to 1 and can make better use of the capacity of the UPS.
