kVA (Apparent Power)

kVA, or kilovolt-amperes, measures the apparent power an alternating-current load pulls from the supply. It is the vector sum of real power (kilowatts, the energy that does useful work) and reactive power (kilovolt-amperes reactive, or kVAR, which sustains the magnetic and electric fields in the load). The classic analogy is a glass of beer: the liquid is real power (kW), the foam is reactive power (kVAR), and the full glass is apparent power (kVA).

Why apparent power matters for a Hashcenter

Utilities, transformers, generators, and PDUs are rated in kVA, not kilowatts, because their conductors and windings must carry the total current regardless of how much of it does useful work. A switch-mode ASIC power supply with active power-factor correction (PFC) keeps its kVA close to its kW draw, so a 3,500 W miner presents roughly 3.5 kVA. Without PFC, the same load could demand noticeably more kVA, forcing you to oversize wiring, breakers, and any generator or UPS feeding the rack.

Estimating your kVA budget

To size service equipment, sum the kVA of every miner, PSU, and ancillary load, then add headroom for inrush and the 80% continuous-load derate. Dividing real power (kW) by the fleet's average power factor gives a working kVA figure. Getting this right prevents nuisance trips and avoids paying for transformer capacity you cannot actually use.

kVA sits at the center of mining electrical planning alongside kVAR (reactive power) and the load factor of your site. Understanding all three keeps your power bill and your panel honest.

Power Factor in Practice

The ratio between real and apparent power is the power factor: PF = kW ÷ kVA, ranging from 0 to 1. Modern ASIC power supplies use active power-factor correction, shaping their input current to track the voltage waveform, which holds PF close to unity — typically above 0.95 under normal load. That is why a mining fleet is an unusually “clean” load in this one respect: its kVA is nearly its kW. But PF sags at light load, so a wall of PSUs idling at a fraction of capacity presents worse PF than the same wall at full mining load — worth knowing when a curtailed or underclocked fleet still occupies transformer capacity out of proportion to its metered energy.

Billing, Penalties, and Demand

Residential meters bill kilowatt-hours and ignore power factor, but commercial and industrial tariffs frequently do not: utilities commonly apply penalties or kVA-based demand charges when a site's power factor falls below a contractual threshold, because the utility's wires and transformers must carry the full apparent current regardless of how much does useful work. A mining operation with high-PF PSUs is usually on the right side of these clauses by default — one of the quiet advantages of the load — but ancillary equipment (ventilation motors, older transformers, lighting) drags site PF down, and it is the site the utility measures. Reviewing the tariff's PF and demand language before signing a supply agreement is cheap; discovering a kVA demand charge on the first bill is not.

A Worked Sizing Example

Take a planned 100 kW of miners. At a fleet power factor of 0.95, apparent power is 100 ÷ 0.95 ≈ 105 kVA. Feeding it through a 112.5 kVA transformer looks like it fits — until you apply continuous-load headroom and remember ventilation, lighting, and networking share the service. Sizing at comfortable margin (utilities and engineers commonly plan transformers well below full nameplate for continuous load) points to the next standard size up. The same arithmetic scales down to a garage: a miner's nameplate watts, divided by PF, is the current your wiring actually carries. That current — not the wattage — is what heats conductors and trips breakers, which is why panels, PDUs, and generators all speak kVAR and kVA while your power bill speaks kW.