Power factor correction gets marketed as a device that “cuts your power bill”. Sometimes it can. Sometimes the site is not billed in a way that creates a meaningful saving, or the proposed equipment is sized from guesswork rather than measurements.
The practical test is simple: does poor power factor increase the demand quantity your business is actually billed on, and would the reduction repay the engineering and installation cost?
I’m Joe from Smarta Switch. We can flag the commercial bill and tariff signals, but correction equipment needs proper electrical assessment and installation. We’re paid by the energy retailer when you switch, never by you.
The short answer
Power factor correction is most relevant when all three are true:
- the site runs substantial inductive loads such as motors, compressors, pumps, refrigeration or manufacturing equipment;
- the tariff or retail contract charges demand in kVA, or the site’s electrical capacity is constrained; and
- measured data shows that poor power factor is materially increasing apparent demand.
If your bill only charges kWh and has no meaningful demand component, correction may still have technical benefits, but the bill saving could be small or indirect.
Power factor in plain English
Three units matter:
- kW is real power doing useful work at that moment.
- kWh is the energy used over time.
- kVA is apparent power, the total electrical capacity the site draws.
Power factor is broadly calculated as:
power factor = kW ÷ kVA
A site drawing 100 kW at a power factor of 0.80 needs 125 kVA of apparent power. The same 100 kW at a power factor of 0.95 needs about 105 kVA.
That does not mean every bill falls by the same percentage. It shows why poor power factor can matter when demand is billed in kVA: the network and equipment must carry more apparent power to deliver the same useful output.
What causes poor power factor
The common cause is inductive equipment. Examples include:
- induction motors;
- refrigeration compressors;
- pumps and fans;
- conveyors;
- welders;
- transformers operating away from their efficient load range; and
- some older lighting and electrical equipment.
Manufacturing, cold storage, food processing, large workshops, water treatment and logistics sites are more likely to have a material issue than a small office with mostly computers and lighting.
The pattern still needs measurement. Two factories with the same equipment list can have different power factors because of operating schedules, motor loading, controls and existing correction equipment.
How poor power factor can affect the bill
Higher kVA demand
If the demand charge is based on maximum kVA, poor power factor can inflate the billed demand even when useful kW output is unchanged. This is the clearest commercial case for correction.
Lost electrical capacity
Higher current for the same useful output can consume capacity in cables, transformers and switchboards. A constrained site may value released capacity even when the electricity bill saving alone is not enough to justify the project.
Additional electrical losses
Higher current can increase losses in the site’s electrical system. The size of that effect depends on the installation and should be calculated, not guessed.
The Australian Government’s large energy user guidance identifies maximum demand and power factor as part of a complete energy-cost review.
A worked screening example
Assume a site reaches:
- maximum real demand: 100 kW;
- existing power factor: 0.80; and
- improved power factor: 0.95.
The apparent demand changes from:
- 100 ÷ 0.80 = 125 kVA, to
- 100 ÷ 0.95 = about 105.3 kVA.
That is a reduction of about 19.7 kVA in apparent demand for the same 100 kW output.
Whether it saves money depends on the actual kVA demand rate, how demand is measured, whether a ratchet applies, when the maximum occurred and whether the correction is active during that interval. A proposal that multiplies 19.7 kVA by one tariff number without checking those details is incomplete.
How to spot the signal on your bill
Look for:
- a demand unit shown as kVA rather than kW;
- maximum kVA and maximum kW readings;
- a demand charge that is a substantial share of the bill;
- a tariff code linked to demand billing; and
- consistent high-demand periods rather than one unexplained event.
If the bill only shows kVA, interval or meter data may be needed to calculate the relationship with kW. Your electricity bill is a starting point, not a power-quality study.
What correction equipment does
Power factor correction equipment commonly uses capacitor banks to supply reactive power closer to the load. Automatic systems switch correction stages as site load changes.
The design needs to account for:
- the measured reactive load;
- operating hours and load variation;
- existing capacitors;
- harmonics from variable-speed drives and electronic equipment;
- switchboard and protection requirements;
- possible resonance; and
- the risk of over-correction at low load.
This is why buying a capacitor bank from a photo of the bill is a bad idea. The equipment must suit the electrical system, not just the monthly invoice.
Power factor correction is not the first move for every site
Before spending capital, check the simpler commercial questions:
- Is the demand tariff correct for the site?
- Is demand billed in kVA or kW?
- Is the retailer passing through or marking up demand costs?
- Did one abnormal operating event set the maximum?
- Can equipment starts be sequenced to reduce the peak?
- Is the energy contract itself competitive?
A tariff correction, retailer comparison or operating change may deliver value without new electrical equipment. On other sites, all four actions belong in the same plan.
How to assess a power-factor opportunity
- Confirm the billing basis. Identify the tariff, demand unit, demand rate and any ratchet or minimum-demand rule.
- Collect measured data. Obtain interval and power-quality data covering normal production, peaks and low-load periods.
- Calculate the avoidable kVA. Compare current kW and kVA, then model a realistic corrected power factor.
- Price the real bill effect. Apply the actual tariff rules across a full year, not a single convenient month.
- Get an electrical design. Use an appropriately qualified professional to assess capacitors, harmonics, protection and installation.
- Measure after installation. Verify power factor, billed demand and any unexpected effects against the baseline.
Questions to ask a supplier
- What measurements were taken, and over what operating period?
- Is the saving based on kVA demand, energy losses or both?
- Which tariff and demand rules were used?
- How were harmonics and resonance assessed?
- What happens when the plant is lightly loaded?
- What maintenance and monitoring are required?
- How will the saving be verified after installation?
If the answer is only “your power factor is low”, the business case is not ready.
Start with the bill, then measure
Upload your recent bill if you want the commercial side checked first. We’ll identify the demand unit, tariff and retailer treatment, and tell you whether a power-factor investigation looks commercially relevant. We do not replace the electrical engineer, but we can help stop you paying for a technical study where the bill shows no likely benefit.
Joe Lawrence, Co-founder, Smarta Switch Australia