Replacing conventional lighting with LEDs usually reduces active energy consumption, yet charges for capacitive reactive energy may appear on the electricity distribution bill. This does not mean every LED luminaire causes extra costs. The first step is to establish what has changed in the site-wide power balance: the characteristics of the drivers, active load or the operation of the existing compensation system.
When can charges rise after switching to LED lighting?
One important scenario arises when replacing the luminaires removes part of the former inductive load while the capacitor bank remains configured for the old operating conditions. The installation may then shift from an inductive to a capacitive balance. A second possible mechanism involves the LED drivers themselves: their input filters and control methods can affect reactive power, particularly at low load or when dimmed.
The installation of LEDs alone is not enough to establish the cause. The effect of the luminaires must be separated from that of other loads, cables and the compensation system. We discuss luminaire selection and energy-savings assessment in more detail in our article on LED lighting modernisation.
How does an LED retrofit change the P and Q balance?
Active power P (kW) represents the power used to perform useful work in electrical equipment. Reactive power Q (kvar) is associated with energy exchanged between the grid and electric or magnetic fields. Both quantities should be monitored together when assessing an installation, ideally at the electricity supply point (PPE, the Polish abbreviation) and on the lighting circuits.
| Change after the retrofit | Possible consequence | What to check |
|---|---|---|
| Active power demand falls | If Q remains similar, its ratio to active power changes. Lower P alone does not establish an increase in capacitive Q. | P and Q profiles before and after the retrofit, and lighting operating hours. |
| Old luminaires and ballasts are removed | Inductive reactive power demand may decrease. | Type and circuit arrangement of the old luminaires; pre-retrofit measurements. |
| The existing capacitor bank remains in service | Energised stages can cause overcompensation once the load decreases. | Controller settings, actual stage switching and the location of the current transformer. |
| Electronic LED drivers are operating | The Q balance and current distortion may depend on driver design and operating point. | Manufacturer data and measurements at full output, during dimming and when switched off. |
It is essential to compare the same site operating conditions. Changes in production, ventilation, transformer operation or photovoltaic generation may affect the results more than the lighting itself.
Why do LED driver specifications matter?
LED drivers differ in their input circuitry, interference-suppression filters and power factor correction (PFC). Some may exhibit capacitive reactive power characteristics. In other cases, the main issue is current distortion rather than phase displacement.
Technical documentation must distinguish the total power factor (PF) from cos φ, the displacement power factor of the fundamental component. PF also reflects the effect of harmonics, whereas cos φ describes phase displacement at the fundamental frequency. A low PF is therefore not, by itself, evidence of capacitive reactive energy. This distinction is explained in the measurement guidance from Schneider Electric.
The operating point also matters. For example, a Signify Xitanium driver datasheet specifies PF = 0.90 and current total harmonic distortion (THD) = 20% at rated output power and supply voltage. These are neither universal LED characteristics nor a guarantee of identical behaviour under dimming. A study of LED street luminaires found that changing the dimming level can significantly affect capacitive reactive power demand and harmonic profiles. Before purchasing, it is therefore worth requesting performance curves for the actual load levels and checking the installation through measurements after commissioning.
When does the distribution network operator charge for capacitive reactive energy in Poland?
As at 29 October 2026, the settlement rules in Poland are set out in § 52 of the Polish Minister of Energy Regulation of 3 September 2026 (Journal of Laws 2026, item 1182). The provision covers capacitive reactive power even when the customer is simultaneously drawing active energy. Reactive energy settlement applies to customers supplied at medium, high and extra-high voltage and may also apply to low-voltage customers. The details should be confirmed against the contract and the tariff of the relevant Polish network operator.
Unlike the settlement of excess inductive reactive energy, capacitive reactive energy does not automatically benefit from a free allowance corresponding to tg φ = 0.4. For billable capacitive reactive energy, § 52(8) provides for a charge calculated by multiplying its quantity by a voltage-dependent factor k and the reference price Crk. Under the current Polish regulation, k is 3.00 at low voltage, 1.00 at medium voltage and 0.50 at high and extra-high voltage, respectively.
On the bill, look for the quantity of capacitive reactive energy in kvarh or Mvarh and the amount charged. The operator may use separate registers and measurement time bands. When interpreting the sign of Q and meter quadrants, follow the meter documentation; do not assume that a minus sign always indicates the same direction of flow.
How can you determine whether the LED retrofit caused the charge?
1. Compare bills and retrofit documentation
Gather electricity distribution bills for the months before and after the retrofit, preferably for comparable periods and the same supply point (PPE). Review active, inductive reactive and capacitive reactive energy separately, together with billing time bands and the date the extra charges first appeared. Use the project records to establish the number and types of old and new luminaires, total system input power, drivers, controls and operating schedule.
If the bill does not distinguish the types of reactive energy, ask the network operator to explain the registers or provide detailed metering and settlement data. The amount charged alone is insufficient to identify the source of the problem.
2. Compare P/Q profiles with lighting operating hours
Where 15-minute P and Q profiles are available, compare them with lighting schedules, production conditions and control-system operation. Check at least the following states: full lighting, partial dimming, lights off and low-load periods such as nights and weekends. If no pre-retrofit history exists, controlled switching tests on individual circuits can help, provided the other loads remain as stable as possible.
An active-energy profile alone cannot replace Q data. At a more complex site, measurements with a power quality analyser are needed at the supply point (PPE) and, to locate the source, on selected circuits.
3. Inspect the existing compensation system
Compare reactive power upstream and downstream of the compensation system where the installation arrangement permits. Check whether capacitor stages are energised at low load, whether the controller reads the magnitude and sign of Q correctly, and whether the current transformer is correctly positioned. Do not alter settings or connections without an installation assessment and a suitably qualified person.
4. Distinguish reactive power from harmonics
For switched-mode drivers, record Q and cos φ as well as PF and current THD. Significant distortion may call for a separate power quality investigation, but it is not equivalent to the capacitive reactive energy recorded on the bill. Installing capacitors does not eliminate harmonics and, under unfavourable conditions, may increase the risk of resonance.
Example: lower active energy consumption but a new line item on the bill
Assume that after the luminaire replacement the facility operates under comparable conditions and its existing capacitor bank remains connected at a constant 12 kvar. The following simplified power values are assumed at the metering point; in this example, a positive sign denotes inductive and a negative sign capacitive reactive power.
| Parameter | Before replacement | After the LED retrofit |
|---|---|---|
| Total site active power P | 70 kW | 45 kW |
| Inductive reactive power of loads before compensation | +18 kvar | +4 kvar |
| Capacitor bank reactive power | −12 kvar | −12 kvar |
| Net reactive power Q at the supply point (PPE) | +6 kvar | −8 kvar |
After the retrofit, the balance becomes capacitive under the stated operating conditions, even though P falls by 25 kW. If Q = −8 kvar were maintained for 8 hours per day over 22 days, the amount of capacitive reactive energy would be 8 kvar × 176 h = 1,408 kvarh, or 1.408 Mvarh. For low-voltage settlement in Poland, the simplified charge under § 52(8) would be 1.408 × 3 × Crk (result in PLN), with reactive energy expressed in Mvarh and Crk in PLN/MWh.
This calculation illustrates the mechanism; it is not a forecast of any particular bill. At a real site, Q, operating schedules and capacitor-stage switching vary over time, and the operator bills energy from the relevant registers and periods. A reduction in P also does not justify attributing every change in Q to LED drivers.
How can the problem be reduced once its cause is known?
| Diagnostic finding | Reasonable next step |
|---|---|
| Unnecessary capacitor stages remain energised after the retrofit | Review the settings, control logic and condition of the existing compensation equipment; assess whether adjustments can resolve the issue without buying new equipment. |
| The Q balance changes when LED lighting is dimmed | Examine the characteristics of the specific drivers and control scenarios; compare options against the actual operating profile. |
| Excess capacitive Q persists at the supply point (PPE) | Only after measurements, consider suitably sized inductive compensation or an active system; compare costs and available control range. |
| Significant harmonics are present | Assess power quality, resonance risk and the technical requirements of any proposed solution separately. |
Compensation equipment should be selected on the basis of the Q profile, harmonics and required control range. Do not size a reactor, capacitor bank or active compensator from the monthly surcharge alone; also check operating costs and the potential effects on other installation operating states.
How can you safeguard your next lighting retrofit?
The request for quotation should specify not only the required lighting levels and active energy savings, but also the electrical operating conditions of the new luminaires. For indoor workplaces, the relevant benchmark for lighting requirements is the appropriate part of Polish standard PN-EN 12464-1:2022-01, applied to specific visual tasks. One illuminance level should not be assumed for the entire facility.
- Require identification of the driver model, input power, PF, phase-displacement or Q data, and current THD, including the measurement conditions.
- For DALI systems and dimming, request data at typical reduced-power levels and in standby mode.
- Before commissioning, inspect the compensation system and assess how it might operate after the load falls.
- Plan acceptance testing and P/Q measurements before and after the retrofit, specifying measurement locations and comparable operating conditions.
- Check whether the proposed lighting controls materially alter the Q profile during dimming periods.
What information is needed for an initial assessment?
If an extra charge appeared after the retrofit, state when the luminaires were replaced, which fixtures and controls were installed, and whether a capacitor bank is in operation. For an initial discussion, provide whatever records you have: before-and-after bills, a driver list, available P/Q profiles, harmonic measurements and information on compensation settings. Missing some of these documents does not prevent us from identifying the next diagnostic steps.
Energy Trend can help define the scope of the analysis and measurements and examine the charge alongside other bill items as part of electricity cost optimisation. Establishing the cause is a sensible first step before deciding on another investment.
What if no pre-retrofit measurements were kept?
Historical bills, documentation for the old luminaires, compensation-system logs and present-day verification measurements can all help. Switching individual LED circuits on and off while keeping other loads as stable as possible can estimate their current contribution to Q. It cannot, however, reconstruct the historical profile with complete certainty; that inference must be clearly distinguished from an actual pre-retrofit measurement.
Sources
- Polish Journal of Laws — Minister of Energy Regulation of 3 September 2026, Journal of Laws 2026, item 1182, § 52 (reactive energy settlement rules in Poland).
- TAURON Dystrybucja — 2026 tariff and explanation of reactive energy charges (example of Polish network operator information; use the tariff applicable to your own supply point).
- Signify — Xitanium 36W driver datasheet (PF and THD specified for a particular operating point).
- Schneider Electric — Power Factor PF and cos φ Measurement (distinction between PF and cos φ, sign conventions).
- T. Lerch, M. Rad, I. Wojnicki — Impact of Dimming LED Street Luminaires on Power Quality (study of the effect of dimming on Q and harmonics).
- Polish Committee for Standardization — notice confirming the replacement of PN-EN 12464-1:2012 by PN-EN 12464-1:2022-01 (publication confirmation; the full standard is a separate document).
