Active power factor correction means the correction of the power factor of an electrical system by equipment in order to reduce power losses in the supply of electricity to that system.
The power factor of an AC power system means the ratio of "real" power (measured in kW) to "apparent" power (measured in VA).
Power factor is always between 0 and 1. Inductive loads such as transformers and motors, or capacitative loads can reduce power factor. Low power factor systems (0.75 and less) incur greater losses.
Active power factor correction will minimise transmission line losses and reduce greenhouse gas emissions. With most electricity contracts, it will also reduce the monthly demand charge paid.
Active power factor correction is only relevant for mid and high-rise buildings with large inductive loads and therefore low power factor.