Why Is Your TNB Bill So High? A Commercial Checklist

Under RP4, a Medium Voltage General site that hits 1,000 kW pays roughly RM89,270 a month in capacity and network charges before a single kilowatt-hour of energy is billed. That is the first thing to understand when you ask why your TNB bill is so high: the answer is usually not "we used more electricity." Medium Voltage energy rates fell to around 29 to 31 sen/kWh when the restructured non-domestic tariffs took effect on 1 July 2025, and the weight of the bill shifted onto the per-kW charges. So if your kWh consumption is flat and the total still jumped, the cause is almost certainly sitting in one of the other four bill components.

Work through the list below in order. Each item names what to look at on the bill first, then what to check in the building.

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

Because a non-domestic bill under RP4 has five separate components, and only one of them tracks consumption. The five are: the energy charge in sen/kWh, the capacity charge, the network charge, a fixed retail charge in RM per month, and AFA (Automatic Fuel Adjustment, which replaced ICPT). Old letter categories such as B, C1, C2, E1, E2 and E3 are retired; you are now on Low Voltage, Medium Voltage or High Voltage, each with a General or Time-of-Use option.

Before you troubleshoot anything, lay this month's bill next to last month's and compare line by line, not total by total. Most "sudden increases" resolve into one line that moved. Our guide on how to read a TNB electricity bill walks through each field if you have not done this before.

1. One bad half-hour set your maximum demand

Medium Voltage demand charges are billed on the single highest 30-minute demand interval in the month, not on your average load. MV General is RM29.43 capacity plus RM59.84 network, so RM89.27 per kW per month. MV ToU is RM30.19 plus RM66.87, so RM97.06 per kW per month.

That means an extra 50 kW recorded once, for half an hour, on one morning, adds roughly RM4,460 to RM4,850 to the bill and keeps it there for the whole month. Chiller start-up stacked on top of an air compressor and a lift bank restarting after a brief outage will do it.

On the bill: find the recorded MD in kW and compare it to the last six months. If it is a step change rather than a drift, one event caused it.

In the building: ask what was started, tested or restarted around the time of that peak. Generator load tests, a plant restart after a Sunday shutdown, and simultaneous chiller staging are the usual suspects. The mechanics of the charge are covered in more detail in maximum demand charge under RP4.

2. A power factor surcharge crept in

A power factor surcharge applies when your PF falls below 0.85 for supply below 132 kV, or below 0.90 at 132 kV and above. It appears as a separate line, and it is easy to miss because it is not proportional to consumption.

Capacitor banks fail quietly. A blown fuse on one step, a stuck contactor, or a controller left in manual after maintenance can drop the site below threshold without any alarm at the switchboard. Harmonics from large VSD populations can also distort what the capacitors are able to correct.

On the bill: look for the PF value and any surcharge line. If PF has been sliding for three months, the bank has been degrading, not failing suddenly. See power factor surcharge in Malaysia for the correction side.

3. AFA moved that month

AFA is a pass-through adjustment in sen/kWh that reflects fuel cost movement, and it can go either way. It is applied across your consumption, so on a high-kWh site a small AFA movement is a large ringgit number.

On the bill: note the AFA rate this month against last month and multiply the difference by your kWh. If that product explains most of the increase, nothing is wrong in your building. Confirm current rates against the official myTNB tariff schedule rather than a spreadsheet someone built in 2023.

4. You are on the wrong tariff option for your profile

General and ToU are priced differently, and the better option depends entirely on when you consume, not how much. ToU carries the higher demand rate (RM97.06 versus RM89.27 per kW on Medium Voltage) but differentiates energy between peak and off-peak, and critically, maximum demand recorded during off-peak hours is not charged.

A 24-hour plant with heavy night production is usually better on ToU. An office tower that only breathes between 8am and 6pm often is not, because its heaviest afternoon load sits inside the peak window and there is little night or weekend consumption left to earn the off-peak rate. A site that switched shift patterns two years ago and never revisited its tariff option is paying for a profile it no longer has.

On the bill: identify your category and option, then re-cost twelve months of interval data both ways before requesting a change. Do not guess. TNB publishes the current schedules on its commercial and industrial pricing page.

5. Your operation drifted into the peak window on ToU

The RP4 peak window is 2:00pm to 10:00pm on weekdays. Off-peak is 10pm to 2pm on weekdays plus all weekends and selected public holidays.

If you are on ToU and your bill rose without a consumption change, check whether work moved into the afternoon. A batch process rescheduled from 11am to 3pm, a second shift extended, or thermal storage charging at the wrong hour will all raise cost while total kWh stays identical.

6. HVAC is running outside occupancy, or fighting itself

Air conditioning is normally the largest single block of a commercial site's load, and it is the most common source of quiet waste. Two patterns dominate: plant running hours that no longer match occupancy (a schedule set for a pre-2020 tenancy, or an override left on after an event), and control loops working against each other, such as reheat fighting cooling, or two AHUs serving one zone with setpoints 2°C apart.

In the building: compare chiller plant start and stop times against actual occupancy for the last month, not against the schedule as documented. Check setpoints and deadbands zone by zone. Look for valves sitting at partial open for hours.

7. Your night and weekend base load is too high

Draw your load profile for a Sunday. Whatever kW you are pulling at 4am on a Sunday, with nobody in the building, is your base load, and you pay for it 8,760 hours a year.

Car park fans running at full speed, façade and signage lighting on a timer that ignores daylight, small AHUs serving empty floors, compressors idling to hold pressure in a leaking ring main, and IT rooms cooled far below what the equipment requires all live here. A 30 kW reduction in base load is around 260,000 kWh a year. At 30 sen/kWh that is roughly RM78,000, and that is before any demand effect.

8. The meter reading or the billing itself is wrong

Estimated reads happen. So do CT and multiplier errors, particularly after a switchboard upgrade, a meter replacement, or a change in supply arrangement.

On the bill: check whether the read is marked actual or estimated. An estimated month followed by a true-up month produces exactly the pattern of "one huge bill" that sends people hunting for a fault that does not exist. Then check that the meter multiplier and CT ratio on the bill match the CT nameplate in your switchroom. If a 1000/5 CT is billed as 1500/5, every figure on that bill is 50 percent high.

Take your own reading at the meter, on a date you record, and reconcile it against the next bill. If they disagree, you have a documented case to raise.

9. Nobody was watching the interval data

This is the cause behind most of the other eight. The demand peak that cost you RM4,800 happened four weeks before anyone saw the bill. By then nobody remembers what was running that Tuesday morning, the CCTV has rolled over, and the shift supervisor who restarted the plant has moved on. The investigation dies and the peak repeats next month.

TNB meters record interval data continuously. Almost nobody reads it until the bill arrives.

Turn the monthly surprise into a daily number

Everything above is diagnosable in advance if someone is looking at load in real time rather than reading a summary 30 days later. That is the practical difference continuous monitoring makes: maximum demand becomes a live KPI you can watch climb toward its previous ceiling, not a line item you discover afterwards.

CobiNeural gives facility and finance teams a running Max Demand figure, per-system breakdowns for HVAC, chilled water and other loads, and alerts over WhatsApp or email when demand approaches a threshold you set, so a peak can be interrupted while it is forming. Anomaly detection catches the quieter items, such as base load creeping up after a maintenance visit or a plant that stopped shutting down on weekends. It runs standalone or as an overlay on an existing BMS, PLC or SCADA, and its reporting aligns with EECA and ISO 50001 workflows.

If you have a bill you cannot explain, send it over with a few months of meter data and we will go through it with you and show you where the cost is being set. Request a demo and bring the worst bill you have.