Why Is Your TNB Bill So High? A Commercial Checklist

Your Tenaga Nasional Berhad (TNB) bill can rise even when your electricity use has not changed. The reason is that several parts of the bill move on their own: the demand charge, the power factor surcharge and the monthly fuel adjustment.

The demand charge is now the biggest of these. Under RP4 (the TNB tariff structure in force since July 2025), a 1,000 kW peak on the Medium Voltage General tariff costs roughly RM89,270 a month, before a single kilowatt-hour (kWh) of energy is billed. At the same time, Medium Voltage energy rates fell to around 29 to 31 sen/kWh on 1 July 2025. So more of the bill now depends on your peak kilowatts (kW) than on your total consumption.

To find what is making your TNB bill so high, compare this month's bill with last month's, line by line. If consumption is flat but the total has jumped, one of the checks below will usually explain it.

In short

• A TNB bill can rise even with unchanged electricity use, since the demand charge, the power factor surcharge and the monthly AFA all move independently of your kWh.
• The demand charge is usually the largest mover: a single high half-hour sets it for the whole month.
• Nine common causes range from a shifted operating tariff to a simple meter or billing error, worth checking before assuming usage itself went up.
• Reviewing interval data, not just the monthly total, is what catches most of these causes early enough to act.

Why is your TNB bill so high when kWh did not change?

The bill can rise because most of it does not depend on kWh. An RP4 bill has five components:

• Energy charge, in sen/kWh.
• Capacity charge and network charge. For Medium and High Voltage customers these are charged per kW of peak demand, not per kWh.
• Retail charge, a fixed amount in RM per month.
• Automatic Fuel Adjustment (AFA), in sen/kWh. The rate changes every month with fuel costs. AFA replaced the Imbalance Cost Pass-Through adjustment.

Only the energy charge and AFA follow your consumption. The demand-based charges can change a lot while your kWh stays the same.

The old letter categories, including B, C1, C2, E1, E2 and E3, have been retired. Customers now fall into Low Voltage, Medium Voltage or High Voltage categories, each with a General or Time-of-Use (ToU) option.

Start by finding which bill line changed. Our guide on how to read a TNB electricity bill explains each field. Then work through the following checks in order.

1. A high half-hour set your maximum demand

Medium Voltage demand charges depend on the highest 30-minute average power demand recorded in the month. This is your maximum demand (MD), and a single interval can set the charge for the whole month.

An extra 50 kW held for one half-hour adds roughly RM4,460 (General) to RM4,850 (ToU) to that month's bill. On the General tariff, that half-hour can happen at any time of day. On ToU, it only counts if it falls in the peak window, 2:00pm to 10:00pm on weekdays. A typical cause is a chiller, an air compressor and a bank of lifts all restarting together after a brief outage and running together for most of a half-hour.

Compare the recorded MD on your bill with the last six months. A sudden jump, rather than a gradual rise, usually points to one event. Ask what equipment was started, tested or restarted around the time of the peak. Common causes are generator load tests, a plant restart after a weekend shutdown and chillers starting together.

Our guide to the maximum demand charge under RP4 explains the calculation in more detail.

2. A power factor surcharge appeared

A power factor (PF) surcharge applies below 0.85 for supplies below 132 kV, or below 0.90 for supplies at 132 kV and above. Power factor describes how effectively the electrical supply is used; kV means kilovolts and identifies the supply voltage. The surcharge appears as a separate line on the bill.

Capacitor banks, which help correct power factor, can fail without an alarm at the switchboard. Check for a blown fuse on a capacitor step, a stuck contactor or a controller left in manual after maintenance. Large numbers of variable speed drives can also introduce harmonics, electrical waveform distortion that affects what capacitors can correct.

Look for the PF value and surcharge on the bill. A PF value that has fallen over three months suggests a capacitor bank that is slowly failing. See power factor surcharge in Malaysia for more on correction.

3. The AFA rate changed

AFA changes with fuel costs and can increase or reduce your bill. It applies across consumption in sen/kWh, so even a small rate change can have a large ringgit effect at a site that uses a lot of electricity.

Compare this month's AFA rate with last month's. Multiply the difference (in sen/kWh) by your monthly kWh, then divide by 100 to get ringgit. If that amount explains most of the increase, the cause is fuel cost rather than anything in your building. Check the current rate in the official myTNB tariff schedule; a spreadsheet built in 2023 may no longer apply.

4. Your tariff option no longer suits your operating hours

The better choice between General and ToU depends on when you use electricity. For Medium Voltage customers, ToU has a higher demand rate, RM97.06 versus RM89.27 per kW, but different peak and off-peak energy rates. Maximum demand recorded during off-peak hours is not charged.

A 24-hour plant with heavy night production usually benefits from ToU. An office tower operating only between 8am and 6pm often does not: its heaviest afternoon load falls within the peak window, with little night or weekend consumption to benefit from off-peak rates. If your shift patterns changed two years ago, your tariff option may still reflect the old schedule.

Check your category and tariff option on the bill. Before requesting a change, calculate what twelve months of interval data would cost under each option. Use the current schedules on TNB's commercial and industrial pricing page.

5. Work moved into the ToU peak window

Moving work into peak hours can raise a ToU bill without changing total kWh. Under RP4, the peak window is 2:00pm to 10:00pm on weekdays. Off-peak hours are 10pm to 2pm on weekdays, plus all weekends and selected public holidays.

Check whether a batch process moved from 11am to 3pm, a second shift was extended, or thermal storage began charging at the wrong hour. Each can raise costs while total electricity use stays the same.

6. Air conditioning runs too long or its controls work against each other

Air conditioning is normally the largest electrical load at a commercial site and the most common source of unnoticed waste. Two operating problems account for much of this:

• Running hours no longer match occupancy. The plant may follow a schedule set for a pre-2020 tenancy, or an override may have been left on after an event.
• Controls work against each other. Reheat may operate while cooling is running, or two air handling units (AHUs) may serve the same zone with temperature setpoints 2°C apart.

Compare the chiller plant's actual start and stop times over the last month with when people occupied the building. Check each zone's temperature setpoints and deadbands, the ranges in which controls take no corrective action. Look for valves that remain partly open for hours.

7. Night and weekend base load is too high

Base load is the power your building draws even when nobody is there. Plot your demand over a Sunday and look at the kW recorded at 4am. That is your base load, which you pay for over 8,760 hours a year.

Check for equipment running unnecessarily:

• Car park fans operating at full speed.
• Façade and signage lighting on timers that ignore daylight.
• Small AHUs serving empty floors.
• Compressors idling to maintain pressure in a leaking ring main, the pipe loop supplying compressed air.
• Computer equipment rooms cooled below what the equipment requires.

Reducing base load by 30 kW saves around 260,000 kWh a year. At 30 sen/kWh, that is roughly RM78,000 before any effect on demand charges.

8. The meter reading or bill is wrong

Estimated readings and metering errors can produce a bill that does not reflect the site's actual use. Current transformer (CT) ratio and meter multiplier errors are possible, particularly after a switchboard upgrade, meter replacement or change in supply arrangement. The CT ratio and multiplier determine how meter readings are scaled for billing.

Check the reading and billing details in this order:

1. Check whether the reading is marked actual or estimated. An estimated month followed by a bill that reconciles actual use can produce one unusually large bill.
2. Compare the meter multiplier and CT ratio on the bill with the CT nameplate in the switchroom. If a 1000/5 CT is billed as 1500/5, every metered figure (kWh and kW) on the bill is 50 percent high.
3. Take your own meter reading, record the date and reconcile it with the next bill. A discrepancy gives you a documented case to raise.

9. Nobody reviewed the interval data

Without regular checks of interval data, the other eight problems can go unnoticed until the bill arrives. A demand peak costing RM4,800 may have happened four weeks earlier, leaving the team to work out what ran that Tuesday morning.

By then, security camera footage may have been overwritten and the shift supervisor who restarted the plant may have moved on. The team loses the evidence needed to investigate, and the peak can repeat the next month. TNB meters record interval data continuously, but it is rarely reviewed before the bill arrives.

Monitor demand while there is time to act

Continuous monitoring lets operators see maximum demand building up during the month, instead of discovering it on a bill 30 days later. It also shows most of the building problems above (demand peaks, long running hours, high base load) while they are happening.

CobiNeural gives facility and finance teams a running maximum demand figure and shows demand by system, including heating, ventilation and air conditioning (HVAC), chilled water and other loads. It sends WhatsApp or email alerts when demand approaches a threshold you set, giving operators time to interrupt a peak as it forms. Anomaly detection identifies less obvious changes, such as base load rising after maintenance or plant that no longer shuts down at weekends.

CobiNeural can run on its own or work with an existing building management system, programmable logic controller or supervisory control and data acquisition system. Its reporting supports workflows under the Energy Efficiency and Conservation Act 2024 (EECA) and ISO 50001, the energy management standard.

If you want to see this on your own bill, our free maximum demand calculator estimates the charge from your kW and tariff. For the full mechanics of a TNB bill, see our free course Understanding Your Electricity Bill.

Send us the bill you find hardest to explain, along with a few months of meter data. We will review it with you and show where the cost is being set. Start at Request a demo.