kVAR (Reactive Power)

kVAR, kilovolt-amperes reactive, quantifies reactive power — the portion of alternating-current power that flows back and forth between source and load without performing useful work. Reactive power is needed to build and maintain the magnetic fields in inductive devices (motors, transformers, chokes) and the electric fields in capacitive devices. It is the foam on the beer: present, real, and something the grid must still deliver and carry, even though it does not turn into heat in your hashboards.

The power triangle

Real power (kW), reactive power (kVAR), and apparent power (kVA) relate as the sides of a right triangle: apparent power is the hypotenuse, so kVA² = kW² + kVAR². The ratio of real power to apparent power — the cosine of the angle between them — is the power factor. High reactive power means a low power factor, which forces conductors, breakers, and transformers to carry extra current for the same useful output. That extra current is not free: it produces real resistive losses in every wire it passes through and eats into the capacity of every upstream component. This is why large commercial and industrial customers are often billed penalties for poor power factor, and why some tariffs meter kVA demand directly — the utility must size its infrastructure for the full apparent-power current, not just the working portion.

What this means for miners

Here miners get good news for once. Modern ASIC power supplies — the APW12 and its peers — use active power-factor correction on their input stage, so a well-designed mining load draws very little reactive power; its power factor sits near 0.95 to 0.99. That keeps kVAR low and avoids power-factor penalties, and it means the current on your feeders corresponds almost entirely to real, hash-producing work. The reactive load in a Hashcenter usually comes not from the miners themselves but from the balance of plant: cooling fans, pumps, and HVAC motors, all classic lagging inductive loads. Sites with many large motors may add power-factor-correction capacitors to inject leading kVAR and cancel the lagging kVAR of the motors, shrinking the apparent-power current and the bill.

The home-mining picture

Residential customers are almost never billed for reactive power — home meters record kWh of real energy — so a home miner does not need to think about kVAR on the bill. Where it still matters is capacity: your panel, breakers, and wiring are limited by current, and current follows apparent power. A near-unity-power-factor ASIC PSU means the nameplate watts translate almost directly into circuit loading, which makes 120V/240V circuit planning refreshingly honest compared with older, poorly corrected loads. If you are running miners alongside big motor loads — a shop compressor, a well pump — the motors, not the miners, are what a clamp meter will reveal as the reactive offenders.

Measuring is straightforward if you want to see the triangle in your own numbers. An inexpensive plug-in power meter shows real watts alongside volt-amperes and power factor for a single 120V device, and clamp-on power meters do the same for whole circuits; multiply volts by measured amps to get apparent power, compare it against the wattage reading, and the gap between them is the reactive component doing its silent round trips. Run that test on an ASIC and the two numbers nearly coincide — the visible signature of active power-factor correction. Run it on an old fan motor or a cheap unregulated supply and the spread widens instantly. Ten minutes with a meter teaches the power triangle more durably than any diagram, and it verifies your specific hardware instead of trusting a datasheet.

Reactive power, real power, and apparent power together define how efficiently your facility uses the grid. Pair this entry with kVA (apparent power) to see the full triangle, and load factor for the time dimension of the same story.