Power Factor

Power factor (PF) is the ratio of real power, measured in kilowatts (kW), to apparent power, measured in kilovolt-amperes (kVA), in an alternating-current system. It is a number between 0 and 1 — often quoted as a percentage — describing how effectively a load converts the current it draws into useful work. A power factor of 1.0, called "unity," means every amp delivered is doing productive work; lower values mean the wiring carries current that accomplishes nothing but still has to be generated, conducted, and paid for in conductor size.

The three powers

Real power (kW) does the actual work: driving ASIC hashboards, spinning fans, producing heat. Reactive power (kVAR) sloshes back and forth sustaining the magnetic and electric fields in inductive and capacitive components — it does no net work but still flows through every wire; see kVAR (reactive power). Apparent power (kVA) is the vector combination the wiring, breakers, and transformers must actually carry. Power factor = kW ÷ kVA. A subtlety worth knowing for electronic loads: classic displacement power factor (current lagging voltage) is only part of the story — rectifier front-ends without correction draw current in narrow distorted pulses, and that harmonic distortion degrades true power factor even when nothing is "lagging" in the textbook sense.

What miners actually present to the wall

Modern ASIC power supplies include active power factor correction (PFC) as their first conversion stage: a boost front-end that forces the input current to follow the sinusoidal voltage waveform before the downstream converters do their work. The result is a near-unity, well-behaved load — Bitmain's APW12, for example, specifies a power factor of 0.99 — with dual PFC stages producing roughly 410–420 V DC internally ahead of the LLC conversion stage. In practical terms, a mining PSU is one of the cleanest large loads you can put on a circuit: its amperage at the wall is essentially its wattage divided by voltage, with almost no reactive overhead.

Why it still matters in a mining setup

Near-unity PF at the machine does not make the topic ignorable — it makes it a planning input. First, circuit sizing: because miner PF is ~0.99, you can size conductors and breakers from real wattage with a small margin, but generators are rated in kVA and typically assume 0.8 PF loads, so a "5 kVA" generator's usable capacity for near-unity mining load is governed by its kW engine rating — check both numbers before trusting the nameplate. Second, billing: residential meters bill kWh only, but commercial and industrial tariffs frequently add penalties or kVA-based demand charges when a facility's aggregate PF sags, so a mining container sharing a service with motor-heavy equipment inherits the site's power factor problem even though the miners themselves are innocent. Third, diagnostics: a miner whose wall-side behavior shows poor power factor or gross current distortion has a sick PFC stage — failed PFC capacitors and front-end faults are among the classic APW-series failure modes a repair bench checks first. A cheap plug-in power meter that displays PF alongside watts and volt-amps is worth having on any mining bench: it turns this entire entry into a five-second measurement, and a reading far below 0.95 on a modern ASIC supply is an early warning worth investigating before the PSU fails outright.

Where to go deeper

Power factor sits alongside voltage and amperage in any electrical plan — know all three before you load a panel. For circuit and outlet fundamentals see the 240V outlet entry, and for planning a whole small fleet on residential service, start with home mining.