🎯 Why It Matters
Power consumption drives three procurement dimensions: (1) Direct energy cost — every watt consumed by a 24/7 fan costs approximately $1/year at $0.12/kWh. (2) Thermal budget — fan power becomes heat that adds to the cooling load in enclosed systems. (3) Electrical infrastructure — apparent power (VA) determines circuit breaker sizing, wire gauge, and UPS capacity. A fan with 30 W active power but only 0.55 power factor draws 54.5 VA — requiring 82% more apparent power capacity than the active power suggests. For DC-powered systems, verify the input voltage range and whether the fan includes an integrated DC/DC converter.
📐 How to Read
Active Power (W) is the real energy consumption — use this for thermal budgeting and energy cost calculation. Apparent Power (VA) is what the electrical circuit must supply — use this for breaker and wire sizing. Power factor = W ÷ VA. For AC fans, PF typically ranges from 0.35 (shaded-pole) to 0.95 (EC with PFC). A PF below 0.5 indicates significant reactive current that generates I²R losses in distribution wiring without doing useful work. For DC fans, PF is not applicable; use W directly. Always verify whether the power rating is "typical" or "maximum" — maximum can be 20–40% higher during startup or at cold temperatures.
📏 Typical Values
AC axial (40 mm, shaded-pole): 1.5–3.0 W / 3.5–6.5 VA. AC axial (120 mm, shaded-pole): 12–25 W / 25–50 VA. AC axial (120 mm, PSC): 8–18 W / 12–28 VA (PF 0.65–0.80). DC/EC axial (40 mm): 0.5–1.5 W. DC/EC axial (120 mm): 2.5–8.0 W. DC/EC axial (200 mm): 15–45 W. AC centrifugal (forward-curved, 120 mm): 25–50 W. EC centrifugal (backward-curved, 175 mm): 20–80 W. EC with active PFC: PF 0.92–0.99. AC shaded-pole without PFC: PF 0.35–0.55. Impedance-protected AC fans: rated power includes locked-rotor wattage derating.
🔗 Related Parameters
fan-efficiency, fan-current-draw, fan-operating-temperature, fan-mtbf
❓ Frequently Asked Questions
Why is VA higher than watts for AC fans?
AC induction motors are inductive loads — the current waveform lags behind the voltage waveform due to the motor's magnetizing inductance. This phase shift means the instantaneous product of volts × amps (apparent power, VA) is higher than the average real power (watts). The magnetizing current circulates between the source and motor without doing mechanical work, but it still flows through breakers, wires, and connectors, generating real I²R heating. This is why circuit sizing must be based on VA (or current in amps), not watts. Power factor correction (PFC) capacitors or active PFC circuits in EC fans reduce this reactive current to near zero.
How much does fan power consumption cost per year?
A simple formula: Annual cost = Power (W) × 8.76 × Electricity rate ($/kWh). For a 20 W fan running 24/7 at $0.12/kWh: 20 × 8.76 × 0.12 = $21.02/year. For a 50 W fan: $52.56/year. In a facility with 200 fans, the difference between 20 W and 35 W fans is $3,153/year. Over a 10-year lifecycle, that's $31,530 in energy savings alone — far exceeding any upfront price difference. Always calculate 10-year TCO when comparing fan options.
What is locked-rotor power and why does it matter?
Locked-rotor power is the power drawn when the fan rotor is prevented from turning (stalled). For impedance-protected AC fans, the winding impedance limits locked-rotor current to a safe level — typically 1.2×–2.5× rated power. For non-impedance-protected fans, locked-rotor power can be 5×–8× rated power and will cause rapid overheating and failure if not externally protected. In safety-critical applications (medical, aerospace), locked-rotor protection is mandatory per UL 507 and IEC 60335-2-80.
How does power consumption change at low voltage?
For AC fans, reducing voltage reduces power roughly as V² — at 90% voltage, power drops to ~81%. However, the fan also produces less airflow and may stall. For DC/EC fans with integrated regulation, input power may actually INCREASE at lower voltages as the internal converter draws more current to maintain output — check the datasheet for the input voltage vs. power curve. Operating an AC fan below rated voltage for extended periods can cause overheating due to increased slip losses.