Solar and Power Factor in Malaysia: A Business Metering Guide

Solar can reduce the active electricity a business imports while leaving part of its reactive demand unchanged. That can make the power factor measured at the grid connection fall, even when the solar plant is generating normally. Before treating a new surcharge as a panel fault, compare the utility meter, the operating loads and the approved inverter settings together.

Three quantities that a solar proposal should keep separate

Active power, measured in kW, does useful work. Reactive power, measured in kvar, is associated with equipment such as motors and transformers. Apparent power, measured in kVA, combines the two. Power factor is a ratio rather than an amount of electricity; the basic relationship is active power divided by apparent power. TNB explains these terms in its power factor guide.

Energy, in kWh, accumulates over time. A solar dashboard may show energy produced by the inverter, while a utility bill reports energy imported at a different measurement point. Neither number alone explains the facility’s power factor. The meter location, time interval and sign convention must be known before comparing records.

This guide concerns a business on a TNB supply in Peninsular Malaysia. It does not transfer TNB billing rules to Sabah, Sarawak or another utility, and it does not imply that every home account carries the same charges as a commercial account.

A worked example: less grid kW does not automatically mean better power factor

The following is an invented, reproducible teaching example, not a HOMI customer result or a bill prediction. Assume balanced sinusoidal conditions, a 100 kW active load and 60 kvar reactive demand. Assume the solar inverter supplies active power only. Grid apparent power is √(P² + Q²), and grid power factor is P ÷ √(P² + Q²). Harmonics, phase imbalance, export and the utility’s billing integration are outside this simplified example.

With 40 kW of solar, grid active power falls to 60 kW. If grid reactive demand remains 60 kvar, the calculated ratio falls from about 0.857 to 0.707. The final row changes the reactive demand to an illustrative 20 kvar and produces about 0.949. It demonstrates the mathematics; it is not a capacitor-bank design or a setting recommendation.

Check the actual supply and the current bill

TNB’s current published thresholds distinguish supply below 132 kV from supply at 132 kV and above: 0.85 and 0.90 respectively. Its power factor surcharge page sets out the charge method. Check the actual tariff, voltage and relevant billing period before applying a threshold. The short example above cannot calculate a monthly surcharge.

Keep the bill that triggered the question and the bill before commissioning. Ask for the meter’s relevant active and reactive energy records and the interval load profile, if available. Check whether production schedules, lightly loaded motors, equipment maintenance or occupancy changed at the same time. A temporal coincidence with solar commissioning is a reason to investigate, not proof of the cause.

A practical review pack for the facility manager

Prepare the single-line diagram, inverter make and model, approved commissioning settings, meter identifiers, commissioning date and a list of large motor-driven loads. Put each reading against a timestamp and operating condition. Include a normal working day and a low-load period so the engineer can see whether the pattern follows solar output, machinery operation or both.

Ask three specific questions: Where is power factor measured? What happens when active grid import becomes small? Is existing correction equipment responding appropriately after solar commissioning? Request a written diagnosis that separates measured findings from assumptions and identifies any further logging needed.

If the contractor recommends changes, ask for the responsible qualified person, the design rationale and the commissioning record. The Energy Commission describes registration for electrical competent persons. Opening switchboards, changing reactive-power controls or adding capacitors belongs with the appropriate electrical team. An owner can collect records without attempting live electrical work.

What to agree before buying correction equipment

A useful scope names the measurement point, the problem being solved, the operating scenarios to test and the evidence required at handover. A larger capacitor bank is not automatically a better answer. Existing controls, operating loads and inverter capabilities need coordinated assessment rather than an isolated product purchase.

Agree how results will be checked after the work: similar operating hours, comparable loads and the same utility meter. Keep energy savings and power factor performance as separate acceptance questions. This makes it easier to understand whether the solar system is performing and whether the facility’s electrical controls suit its new daytime operating pattern.

For a first conversation, review HOMI’s solar services and contact HOMI with the bill period and the equipment details. Share private account information only through an agreed private channel. HOMI should first identify what is known and what needs a competent electrical assessment, rather than promise a universal surcharge saving.

This article reflects official information checked on 8 October 2026 and is general guidance. Programme rules, tariff treatment, approval and actual savings remain subject to the latest PETRA, SEDA, Energy Commission and TNB requirements plus the property bill, roof and usage pattern.