What is a BESS?
A BESS (battery energy storage system) is a facility-scale battery with its own inverter and controls that charges from solar or the grid and discharges on command. Battery energy storage in Malaysia is used by commercial and industrial sites for three jobs: shaving the maximum-demand peak, shifting surplus solar into the evening, and backing up critical loads.
Who BESS is for
BESS is for Malaysian commercial and industrial sites that want to control when they draw power from the grid, not just how much. Three groups make up most of the enquiries this page is written for: facilities on a medium- or high-voltage tariff that carries a maximum-demand charge and want to shave that peak; sites with an existing or planned solar system that would rather store surplus generation than export it at a lower credit rate; and operations — cold rooms, server rooms, production lines — that cannot tolerate even a short outage on part of their load.
This page covers facility-scale battery storage, typically sized from tens to several thousand kilowatts and kilowatt-hours. It is not about a household battery bolted onto a rooftop solar system — for that, see Trexon's home battery storage and the battery hardware we install. Facility-scale BESS is also frequently one component inside a wider microgrid strategy that combines generation, storage and site controls, rather than a standalone purchase.
How does GITA work for solar in Malaysia in 2026?
Current rules, until 31 December 2026. A company that owns a solar system for its own use can claim GITA Asset at Tier 2: an allowance of 60% of qualifying capital expenditure, set against up to 70% of statutory income. Under the current MGTC guideline the capex must be incurred, the system commissioned and the GITA Asset application received by MGTC by 31 December 2026 — the application can only be filed after commissioning. A system the company does not own does not qualify, because the claimant must own the asset.
From 1 January 2027 — proposed under Budget 2027, subject to legislation. The Budget 2027 tax measures propose extending GITA Asset to purchases verified by MGTC up to 31 December 2030, with two changes that matter for solar: a standalone solar system is no longer listed, and solar integrated with battery storage (BESS or ESS) moves to Tier 1 at 100% of qualifying capital expenditure, still set against up to 70% of statutory income. Companies would have to apply to MGTC within 24 months of purchase. These are announced proposals, not yet gazetted, and MGTC has not published its updated guideline or asset list. How a 2026 purchase verified in 2027 will be treated has not been published either, so plan to commission and apply in 2026. Source: MOF Budget 2027 Tax Measures, Appendix 25.
For a storage buyer the point is that a battery integrated with solar is on the proposed Tier 1 list, while a solar-only system is not. The tax incentives section below covers how BESS itself is treated; the claim mechanics are in the GITA guide for companies.
Why the maximum-demand line matters for storage
Many commercial and industrial TNB tariffs bill on more than the electricity consumed. Alongside the energy charge, several categories add a maximum-demand (MD) charge: a RM-per-kW rate applied to the single highest 30-minute demand interval recorded anywhere in the billing month, shown as its own line on the bill. Because that charge is set by one interval, not the whole month's usage pattern, it rewards flattening a single spike far more than trimming daily consumption generally — which is exactly what a battery is good at.
Not every tariff carries this line. Trexon's own tariff model flags a maximum-demand charge as present or absent per category: the Non-Domestic Low Voltage tariff (formerly Tariff B and Tariff D) used by most shops, small offices and small industrial premises carries none, while the medium- and high-voltage categories most factories and larger sites sit on do, some split into time-of-use peak and off-peak periods (weekday peak hours run 14:00–22:00, Monday to Friday). Whether your site has an MD line at all is the first question a BESS assessment answers, because it changes what the battery is actually being bought to do — see our explainer on how the TNB maximum-demand charge is billed and reduced.
A related but separate bill line — the power-factor / kVArh penalty — is not something battery storage corrects on its own; our power-factor penalty guide covers that charge in full.
Can BESS provide backup power during outages?
Yes, but only for loads wired to it, and only with the right equipment — "backup" needs to be designed deliberately rather than assumed. A standard grid-tied solar system shuts itself down in a power cut (anti-islanding protection, a safety requirement so the system does not feed a line utility crews think is dead), so solar panels alone do not keep the lights on. Adding a battery changes that only when it is paired with an automatic transfer switch or a hybrid inverter's island mode, and only for the loads that switchboard is wired to protect — usually a defined "critical load" list rather than the whole site.
How long backup lasts is a direct function of how much energy (kWh) the battery holds against how much power the protected loads draw, not a fixed duration this page can promise. That is why the critical-load list — what must stay on, and its combined kW draw — is one of the first inputs a BESS assessment collects; see the sizing method below.
Can BESS cut TNB maximum-demand charges?
Yes, where your tariff has an MD charge. A behind-the-meter battery sits between the site's electrical loads and the TNB meter, so it can be programmed to discharge exactly when it is needed — either reacting to real-time demand or following a schedule built from the site's known load pattern. When the site's demand approaches the target maximum-demand level, the battery supplies the difference itself, so the amount TNB's meter actually records during that 30-minute interval stays below what the site is really drawing. The whole month's maximum-demand charge is set by that one interval, so shaving it there is enough — the battery does not need to run all day.
This only reduces a bill where the tariff has a maximum-demand charge to begin with (see the section above); on tariffs without one, the value case moves to time-shifting and backup instead. A dedicated peak-shaving system, with or without solar, is covered on our peak-shaving page.
Sizing a BESS: power, energy and duration
A BESS is specified on three linked figures, not one. Power (kW) is the maximum rate the battery can charge or discharge at a given instant — it has to cover the largest demand spike or the combined draw of the critical loads it protects. Energy (kWh) is the total amount of electricity the battery can store — it has to cover how long that power needs to be sustained. Duration is simply energy divided by power, in hours, and is often the figure a shortlist of products gets built around once power and energy are known.
Two adjustments always shrink the usable numbers below a battery's nameplate rating: round-trip efficiency (charging and then discharging a battery loses some energy as heat, so less comes out than went in) and depth-of-discharge margin (most chemistries are specified to cycle only within a safe state-of-charge band, to protect battery life, rather than the full range). Both vary by chemistry and product, so this page does not publish a percentage for either — a real design adds both margins on top of the raw kW/kWh figures below.
A defensible sizing exercise starts from interval load data, your maximum-demand history, and a critical-load list — see what a BESS assessment needs below for the full input set. Where solar is part of the design, Trexon designs around Jinko 620W N-type modules with Solis, Huawei, Sungrow or GoodWe string or hybrid inverters, selected per site.
Sizing method: covering an assumed demand excess for two hours
Illustrative example — labelled assumptions, not a quotation
- Assumed maximum-demand excess
- 150 kW
- Source: Illustrative assumption for this example only
- Assumed coverage duration
- 2 hours
- Source: Illustrative assumption for this example only
- Power rating needed: battery power ≥ assumed demand excess = ≥150 kW
- Energy capacity needed: power × duration = ≥300 kWh
Before efficiency and depth-of-discharge margins are applied — round-trip losses and a discharge floor both push the specified battery above these raw figures. This illustrates the method only; a real number needs your interval load data and maximum-demand history, not this page.
Solar-only, solar-plus-BESS or BESS-only: what each configuration solves
Not every site needs all three. The right configuration follows from which problem you are actually solving — energy-charge savings, maximum-demand control, backup, or some combination — and the table below sets out what each does and does not address.
BESS is often added to an existing or planned solar system — see industrial solar — rather than bought as a separate project. Solar ATAP caps a non-domestic installation at 100% of the site's maximum demand in AC inverter capacity (kWac), with a hard cap of 1,000 kW per installation (GP/ST/No. 60/2025 §8.3, §8.5) — and that cap is measured in AC capacity, not DC panel capacity (kWp), so a DC-oversized array feeding a hybrid inverter with battery buffering is a recognised way to capture more usable solar without exceeding the cap. Multi-tenant premises are not eligible for Solar ATAP (§6.1(d) of the guidelines); single-occupier premises with their own TNB account can apply. See our peak-shaving primer for industrial parks for a worked scenario.
| Configuration | What it solves | What it does not solve |
|---|---|---|
| Solar-only | Cuts the energy-charge portion of the bill. Solar alone does not reduce maximum demand reliably — one cloudy half-hour sets the month's MD. | No backup during an outage (grid-tied inverters must disconnect); no maximum-demand control outside daylight hours. |
| Solar + BESS | Time-shifts surplus solar into hours it would otherwise be exported, and can discharge on demand to shave the maximum-demand peak — including outside daylight hours. | Needs accurate sizing against real interval data; an oversized battery adds cost without adding savings. |
| BESS-only (no solar) | Targets the maximum-demand charge directly by discharging during the billing peak, and can back up critical loads. | Captures no solar energy-charge savings — relevant only where the maximum-demand or backup case stands on its own. |
Qualitative comparison only. Actual outcomes depend on verified load, tariff and equipment data, not this table.
Tax incentives: GITA for battery storage
Battery energy storage bought for a company's own use can qualify for the MGTC Green Investment Tax Allowance (GITA) Asset. BESS is a GITA Asset Tier 1 asset: an allowance of 100% of qualifying capital expenditure, set off against up to 70% of statutory income in a year of assessment (solar PV for own consumption is Tier 2, at 60%). All claims are subject to MGTC verification. To claim, the capex must be incurred, the system commissioned and the MGTC application submitted by 31 December 2026, and only the company that owns the asset can claim. The GITA Asset window, per the current MGTC guideline, runs to 31 December 2026.
Indicative only. Subject to MGTC verification, applicable tax law and confirmation by the customer’s licensed tax adviser. The system must be commissioned and the GITA Asset application submitted to MGTC by 31 December 2026.
Read the full mechanics — what counts as qualifying expenditure, how the claim is filed, and how it interacts with normal capital allowances — in our GITA tax incentive guide.
From project brief to commissioning
A BESS project moves through the same disciplined sequence regardless of size. It starts with the brief below — facility type, tariff category, and whatever load, maximum-demand or critical-load information you already have. Trexon's engineering team then reviews the available interval data and bills, defines the design case (maximum-demand control, backup, solar time-shifting or a combination), and checks the practical constraints: switch-room space, transformer capacity, protection settings and, where relevant, how the battery interacts with an existing or planned solar array under the Solar ATAP rules.
Where GITA is being claimed, tax structuring is confirmed with the customer's own adviser before capital expenditure is committed. The project then proceeds to detailed design, procurement, installation and commissioning, with protection and control settings tested and monitoring set up before handover.
This page deliberately does not attach durations to that sequence — a shop-lot system with no maximum-demand charge and a multi-megawatt-hour industrial system on a factory floor move through it at very different paces, and a page-level promise would not be true for either.
