What Is Power Factor Correction?
A practical explanation of how PFC reduces reactive power charges, improves efficiency and lowers your electricity costs.
Understanding Power Factor
In simple terms, power factor is a measure of how efficiently your electrical system uses the power supplied by the grid. Industrial sites with motors, compressors, welders or HVAC equipment often draw more power than they actually use. This wasted energy is known as reactive power, and the utility charges you for it.
Power Factor Correction (PFC) reduces this wasted energy by installing capacitors or automatic systems that balance the electrical load. The result is lower bills, fewer penalties and a more efficient network.
How Power Factor Works
Below is a simplified representation of real power, reactive power and apparent power:
Power Factor = kW ÷ kVA. Improving power factor reduces the kVAr component, lowering your overall demand.
Why Power Factor Correction Matters
Types of Power Factor Correction
Fixed PFC
Simple capacitor banks used for steady loads such as pumps or fans.
Automatic PFC
Multi‑step systems that adjust to changing load conditions using contactors or thyristors.
Detuned / Filtered PFC
Used where harmonics are present. Protects capacitors and prevents resonance issues.
Real-Time PFC
Static VAr Generators (SVG) respond to load changes within milliseconds, ideal for rapidly varying loads. Where high harmonic distortion is present, Active Power Filters (APF) cancel harmonic currents in real time without the resonance risk of passive capacitor banks.
Frequently Asked Questions
Is power factor correction worth it?
For most sites with a power factor below 0.95, yes. Typical payback can be 12–18 months from eliminating reactive power penalties alone, after which the equipment continues saving money for its 10-20 year service life subject to regular PFC servicing.
How much does power factor correction cost?
Costs vary by site size and load. A small fixed capacitor bank typically starts from a few hundred pounds, while larger automatic or high-voltage systems can run to £50,000+. A site survey gives an accurate, properly sized quote rather than a guess.
What is a good power factor?
Most UK electricity suppliers apply reactive power charges once your power factor drops below 0.95. A well-corrected site should sit between 0.95 and 0.98 lag. It's best to avoid over-correcting into a leading power factor, as this can also attract charges and cause voltage or stability issues on the network.
How long does installation take?
Most low-voltage installations are completed in 1–2 days with minimal disruption to your operation. High-voltage (11kV) systems may require a planned outage window, which we schedule around your operational needs.
Will power factor correction reduce my kWh usage?
PFC mainly removes the reactive power charge from your bill rather than reducing your KWhr (real power) consumption. However, it does reduce losses in your cables and transformers, which can produce a small additional saving, especially if you are metered on the high voltage side.
Do I need a survey before buying equipment?
Yes. Installing the wrong size or type of equipment can fail to fix the problem, or in sites with significant harmonics the capacitors can catastrophically fail or cause damage through resonance. A survey identifies your actual load profile and harmonic levels so the right solution is specified first time.
What's the difference between fixed and automatic power factor correction?
Fixed PFC uses a single capacitor bank sized for a steady load, such as a constantly running pump or fan. Automatic PFC uses multiple steps that switch in and out as your load changes throughout the day, keeping your power factor corrected even on sites with variable demand.
Can power factor correction equipment be damaged by harmonics?
Yes — standard capacitors can be damaged or create resonance problems on sites with high harmonic distortion (common where there are VSDs, UPS systems or large volumes of LED lighting). In these cases we specify detuned or filtered PFC equipment designed to operate safely alongside harmonics.
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