A sub meter is a private meter installed on the customer side of the Tenaga Nasional Berhad (TNB) supply meter. It records how many kilowatt-hours (kWh) one room, circuit, or appliance group uses, so the people in a shared house can split the TNB bill by actual use. Installing one does not change the TNB account, which stays in the name of one registered account holder for the whole property.
This article explains what a sub meter measures, how room readings relate to the TNB bill, the four setups common in Malaysian room rentals, and how billing models pair with the hardware.
Updated October 2026. Guide for landlords, tenants, and property agents on shared rentals in Peninsular Malaysia, not legal or tenancy advice.
Table of Contents
What a sub meter measures on a rental property
A sub meter records kWh on the customer side of the TNB meter, so it covers only the part of the property wired to it. Its readings do not feed TNB’s billing. The owner or manager uses the figures to allocate costs inside the house. Some sub meters are postpaid, with usage invoiced after each period. Others are prepaid, with occupants buying credit before they use power.
Sub meter compared with the TNB Smart Meter
The TNB Smart Meter is an Advanced Metering Infrastructure (AMI) device. According to myTNB, it records electricity usage and sends it to TNB for monitoring and billing. TNB installs it at no charge to the registered customer. The smart metering guide for landlords walks through how that device differs from a private room meter. The table below compares the two.
| Feature | Sub meter | TNB Smart Meter |
|---|---|---|
| Installed by | Owner or manager, through a registered electrical contractor | TNB, at no charge to the registered customer |
| Measures | One room, circuit, or appliance group | The whole property supply |
| Readings go to | Owner, manager, or occupants | TNB, for monitoring and billing |
| Role in the TNB bill | None; used to split the bill inside the house | Basis of the TNB bill |
| Where usage is viewed | Owner dashboard, display, or app (vendor-specific) | myTNB app |
How sub meter readings relate to the TNB bill
TNB bills the registered account holder for the whole property, not for each room. TNB’s Owner / Tenant Issues FAQ gives owners two options before a tenant moves in. The first is to complete a Change of Tenancy (COT), which makes the tenant fully responsible for the account. The owner then loses the right to disconnect if the tenant defaults. The second is to keep the account in the owner’s name and monitor usage and payments through myTNB.
Sub meter readings become Ringgit Malaysia (RM) amounts through the blended rate on the actual TNB invoice. The blended rate is the total TNB amount payable for the billing period, divided by the total kWh on that bill. If a house uses 500 kWh in a month with RM300 payable, the blended rate is RM0.60 per kWh. A room whose sub meter records 100 kWh is allocated RM60 for that period at that rate. The TNB electricity tariff guide for rentals shows where both figures appear on a Peninsular domestic bill.
Room sub meters rarely add up to the TNB total. Common-area lighting, a shared water pump, corridor sockets, and wiring losses are not on any room meter, so room readings come in below the licensed meter total. Cobler’s tenant billing guide makes the same point for check meters in commercial buildings. The house rules name how that gap is shared, so the allocation still ties back to the TNB invoice.
Four sub meter setups used in Malaysian room rentals
Most shared houses pick one of four paths. Each measures a different slice of the installation, and the right choice depends on how the distribution board is wired today.
Aircond-only sub meter
An aircond-only sub meter is wired to the air conditioning circuit, which often already has its own breaker in Malaysian houses. Lights and sockets stay on other circuits and are usually handled through rent or a separate rule. This setup isolates the load that drives most variable cost in tropical room rentals, without rewiring every bedroom. The sub-meter installation cost guide covers wiring and typical price ranges. The aircond electricity cost guide covers running costs.
Per-room circuit sub meter
A per-room circuit sub meter measures the breaker group feeding one bedroom’s lights and sockets. It is the cleanest model when each room already has an isolated circuit. The Energy Commission’s residential wiring examples group socket outlets by load type rather than by bedroom, so many converted family houses still share one socket breaker across two rooms. A true per-room circuit often means new cable and breakers before the meter is fitted. The installation cost guide compares that rewiring cost with lighter options.
Formula metering when two rooms share a circuit
When two rooms still feed from one incoming breaker, separate per-room circuits are not always practical. One pattern is to meter the shared line and meter the branch to Room 2 only. Room 1 is then the shared-line reading minus the Room 2 reading, provided the Room 2 branch meter sits downstream of the shared-line measurement. Platforms such as PowerLah let owners store that subtraction as a room formula instead of pulling new cable through occupied walls. The installation cost guide walks through a two-meter example against a partial rewire quote.
Socket sub meters added as one room total
Socket sub meters clip onto or replace selected outlets, so high-draw appliances plugged into them are tracked. Several socket readings in one bedroom can be added into a single room total when every outlet that matters is on the list. Any unmetered socket still draws power without showing on the room total. This approach suits rooms where tenants run PCs, kettles, or other plug loads while aircond stays on its own circuit. The prepaid electricity meter guide covers device choice and prepaid behaviour.
Billing models that pair with sub meters
Sub meter hardware works best with a defined billing model and written house rules. Postpaid pass-through applies each room’s kWh at the blended rate from the latest TNB bill. Prepaid room meters deduct credit as kWh are used, so occupants pay upfront before heavy aircond usage. The prepaid electricity meter guide covers top-ups and zero-credit behaviour.
House rules for either model usually specify how common-area electricity is split, how vacant rooms are treated, and how leftover prepaid credit is handled at move-out. The fair utility billing guide compares how shared houses split one master account when usage differs by room.
Installation and safety basics
Sub meter work changes the electrical installation after the licensed TNB meter, so it is carried out by a contractor registered with the Energy Commission (Suruhanjaya Tenaga, ST). ST lists registered electrical contractors on its register of contractors page. The contractor checks cable size, breaker rating, and board space before fitting the meter. Online wiring diagrams cannot show one house’s load or board layout, so this is licensed trade work, not a do-it-yourself job. Typical meter and labour bands are in the installation cost guide.
Frequently asked questions
A prepaid sub meter controls only the circuit it is wired to, so a zero-credit cutoff on that meter stops supply on that circuit only. When each bedroom has its own sub meter and its own credit balance, one room can lose power while housemates on other meters keep theirs.
Corridor lights, the kitchen, and a shared bathroom are often left on the main TNB side of the board rather than on a room sub meter, so those areas can stay lit even when one bedroom’s prepaid credit runs out. The house rules or a labelled meter board record which outlets and lights each room meter actually feeds.
When prepaid is in use, the same rules usually name the minimum top-up amount, which circuits the room meter controls, and that supply to those circuits pauses until credit is restored. The prepaid electricity meter guide covers top-ups and zero-credit behaviour in more detail.
Strictly speaking, a landlord should not profit from TNB’s electricity supply. A defensible pass-through reconstructs the tenant’s share of the real bill at the blended rate from the TNB invoice, with no margin on the energy itself. Cobler states that marking up the kWh price turns cost recovery into a sale of electricity, which needs a licence in Peninsular Malaysia.
Many operators still add a markup to metered kWh to cover costs that the blended rate does not capture, and some of those costs are real. Sub meter readings can drift or be disputed, and the owner pays for recalibration or replacement. The Automatic Fuel Adjustment (AFA) on the TNB bill changes from month to month, so a kWh rate fixed in the tenancy agreement leaves the owner carrying the swings. The blended rate is also an average over the whole house. Because the Peninsular domestic tariff is tiered, a heavy month can push the house into higher-priced bands that raise the rate for every room. High-draw appliances such as air conditioners add servicing and repair costs that grow with use and fall on the owner.
Many sub meter providers let the owner or landlord set only a fixed price per kWh. As a result, owners typically set a high amount just “to be safe”, leading to tenants paying a much higher cost and potentially expose the owners to higher risk of fines. In contrast, PowerLah’s platform is built on the core principles of fairness and transparency, which builds in live tariff calculation so the actual price per kWh stays close to TNB’s rate without needing the owners and tenants to do manual calculation.
No. People often search sub meter and TNB together because both readings sit in the same billing workflow, but only TNB’s licensed meter sets the utility invoice. A room sub meter is downstream of that device. TNB keeps billing from its own meter, whether that is a conventional unit or a TNB Smart Meter.
TNB pursues the registered account holder on the supply contract. If the owner kept the master account, TNB’s Owner / Tenant Issues FAQ notes that some owners are left with large bills after tenants move out. After a Change of Tenancy, the tenant is the registered user TNB chases, but the owner no longer has the right to disconnect if the tenant defaults. Any remaining sub meter balance is a private matter under the tenancy or house rules, not a TNB debt.
What stays on the TNB account after you add sub meters
The registered account holder still settles one TNB bill for the whole premise. Tariff thresholds, fuel adjustment, retail charge waivers, and other lines on a Peninsular domestic bill apply to the account’s total kWh, not to each room meter. Room sub meters explain how that total is shared inside the house. The TNB electricity tariff guide for rentals describes how those components read on a shared rental account.
References
Sources
- Owner / Tenant Issues — Tenaga Nasional Berhad, current page. Accessed 2026-10-21.
- Smart Meter — myTNB, current page. Accessed 2026-10-21.
- Register as Contractors — Suruhanjaya Tenaga, current page. Accessed 2026-10-21.
- Tenant Electricity Billing in Malaysia: Rules & Setup — Cobler, 24 June 2026. Accessed 2026-10-21.