Reactive energy (energía reactiva)

What reactive energy is

Reactive energy is drawn from the network by some equipment and returned without turning into useful work. Motors, transformers, compressors and pumps need it to build their magnetic fields. It moves nothing and heats nothing, but it flows through the cables, takes up network capacity and causes losses. That is why business bills penalise it. It is the “Reactiva” line some expats spot on an Endesa bill.

Active, reactive and apparent power

• Active power (kW): the power that does the work: turning a motor, giving light, heating.
• Reactive power (kVAr): exchanged with the network to keep magnetic fields going.
• Apparent power (kVA): the combination of both; what cables and transformers really have to carry.

Reactive energy can be inductive, from motors and transformers, which is the usual kind, or capacitive, which appears with a lot of electronic equipment or a badly adjusted correction system.

Reactive energy and power factor

Reactive energy is a quantity measured in kVArh and shown on the bill. The power factor (cos phi) is a number between 0 and 1 showing how much of the energy flowing is useful. The more reactive energy, the lower the cos phi. Below 0.95 a surcharge applies.

When it affects you

The domestic 2.0TD tariff does not charge for reactive energy. Tariffs over 15 kW do: warehouses, workshops, hotels, shops with lots of refrigeration and residential buildings with pumps and lifts (elevators). If your bill shows an amount for energía reactiva, you are paying for something that can be removed.

How to remove it

The usual fix is a capacitor bank, which produces the reactive energy the motors need on site so they do not take it from the network. See power factor correction in Seville, Spain.