MS 1525:2019 Chiller Efficiency Requirements Explained: Does Your Air-Cooled Chiller Still Comply?

There are two questions hiding inside “does my chiller comply with MS 1525,” and they have different answers.

The first is legal: am I actually required to meet it? For most existing plant in Malaysia, the honest answer is no — and anyone telling you otherwise is either selling something or has not read the by-laws.

The second is commercial: would my chiller pass today’s minimum if it were assessed? That question matters a great deal, because MS 1525 compliance is the gate on a government rebate that closes at the end of 2026, it is written into most consultant specifications, and it is the yardstick your energy auditor will reach for under the new energy efficiency legislation.

This article separates the two, explains the three efficiency numbers the standard works with, and sets out how to check an air-cooled chiller you already own.

One note before starting: MS 1525:2019 is a copyrighted Malaysian Standard sold by the Department of Standards Malaysia. This article explains how the requirements are structured and how to work with them. It does not reproduce the efficiency tables. If you are specifying or assessing equipment, buy the standard.

What MS 1525:2019 actually is

The full title is Energy efficiency and use of renewable energy for non-residential buildings — Code of practice. The 2019 edition is the third revision, following versions in 2001, 2007 and 2014. It covers passive design, building envelope, lighting, electrical distribution, air-conditioning and mechanical ventilation, energy management systems and building energy simulation.

The chiller efficiency requirements sit in the ACMV section, in a table covering electrically driven water chilling packages, broken down by equipment type and size category. SEDA’s own chiller rebate guideline points to Table 25 of the standard for the minimum kW/TR ratings.

Now the part that gets misreported. Malaysian Standards are voluntary by default. The standard says so itself: compliance with a Malaysian Standard does not of itself confer immunity from legal obligations. A Malaysian Standard becomes mandatory only where a regulator makes it so through regulations, by-laws or similar instruments.

What is actually mandatory, and what is not

The Uniform Building By-Laws were amended in 2012 to add By-law 38A on energy efficiency in buildings. It requires that new or renovated non-residential buildings with air-conditioned space exceeding 4,000 square metres be designed to meet the requirements of MS 1525 with regard to OTTV and RTTV, and be provided with an energy management system. It also sets roof U-value limits.

Read that carefully. By-law 38A pulls in the building envelope provisions — Overall Thermal Transfer Value and Roof Thermal Transfer Value — plus an energy management system. It does not pull in the chiller efficiency table. There is no general legal requirement in Malaysia today that your chiller meet the MS 1525 minimum COP, and researchers looking at Malaysian building energy policy have repeatedly noted that the country still lacks comprehensive energy efficiency legislation for buildings, with MS 1525 functioning largely as a guideline.

Bear in mind too that building by-laws are adopted at state level, so local requirements vary. Check with the authority having jurisdiction for your site rather than assuming.

So if it is not legally binding, why does it matter?

It gates the SEDA chiller rebate. Under the NUR:CHILLER programme, replacement chillers must comply with the minimum kW/TR stipulated in MS 1525:2019. No compliance, no money. More on this below.

It is written into specifications. Consultants and developers routinely specify MS 1525 compliance in tender documents. At that point it becomes contractually binding even though it is not statutory.

Green Building Index assessment leans on it. If the building is chasing or holding a GBI rating, MS 1525 is the reference point.

It is the natural benchmark under EECA 2024. The Energy Efficiency and Conservation Act came into force on 1 January 2025, repealing the older EMEER 2008 regulations on the same date. Facilities in Peninsular Malaysia and Labuan consuming 21,600 GJ or more per year must appoint a Registered Energy Manager, run an energy management system and complete mandatory audits, with penalties reported at up to RM100,000. When a registered energy auditor assesses your chiller plant, MS 1525 is the standard they will measure against — not because the Act names it as a chiller mandate, but because it is the Malaysian reference that exists.

The practical position, then: not compulsory for most existing plant, but increasingly the number that decides whether you get paid, get certified, or get a clean audit.

The scope trap: comfort cooling is not process cooling

This one catches industrial operators constantly.

MS 1525 is a code of practice for non-residential buildings. Its ACMV provisions are aimed at air-conditioning and mechanical ventilation — cooling people and building spaces. A chiller supplying a factory’s office block, canteen and clean room air handling is squarely in that territory.

A chiller holding a plating bath at 15°C, cooling injection moulds, or serving a batching plant at 0°C is doing something different. It is process cooling, it is often selected for a leaving fluid temperature nowhere near the 6.67°C standard rating condition, and it is not what a building energy code was written for.

This distinction has money attached. SEDA’s NUR:CHILLER rebate is described as covering energy-efficient cooling system replacement for comfort cooling purposes. If your application is process cooling, do not build a business case around that rebate without confirming eligibility with SEDA first.

It also affects how you should read any efficiency comparison. A process chiller pulling down to 0°C will show a far worse kW/RT than a comfort chiller making 7°C water, and that is physics, not poor engineering. Comparing the two against the same table is meaningless.

The three numbers, and what each one hides

Chiller efficiency in this context gets expressed three ways.

Full-load COP. Coefficient of performance at the standard rating point: cooling output divided by power input, both in kW. Higher is better.

kW/RT. Power input per refrigeration ton. Lower is better. The two convert directly:

kW/RT = 3.517 ÷ COP

So a COP of 3.0 is 1.17 kW/RT, and a COP of 3.5 is 1.00 kW/RT. Malaysian specifications tend to use kW/RT, international manufacturer data tends to use COP or EER, and a surprising number of comparison errors come from people not converting before comparing.

IPLV — Integrated Part Load Value. A single weighted figure representing part-load performance, defined by AHRI 550/590. The weighting is heavily skewed away from full load:

IPLV = 0.01A + 0.42B + 0.45C + 0.12D

where A, B, C and D are efficiency at 100%, 75%, 50% and 25% load. Only 1% of the weight sits at full load. Nearly nine-tenths sits at 75% and 50%.

That weighting is sensible in principle — chillers rarely run flat out. The problem is the conditions those part-load points are measured at.

Why IPLV flatters air-cooled chillers in Malaysia

Under AHRI 550/590, an air-cooled chiller’s standard full-load rating is taken at 35°C entering condenser air dry bulb, with 6.67°C leaving chilled water. Fine — 35°C is a plausible Malaysian afternoon.

The part-load points are where it falls apart. The 75% load point is rated at roughly 26.7°C ambient, and the 50% and 25% points step down further, into ambient temperatures that essentially do not occur in Peninsular Malaysia at any hour of any day. The weighting scheme was derived from averaged weather across a set of US cities, with and without airside economisers. It describes a climate we do not have.

The consequence is straightforward. An air-cooled chiller quoted with an impressive IPLV is being credited for efficiency at cold-ambient operating points it will never see on your roof in Shah Alam. Its real annual performance will be closer to its full-load figure than the IPLV suggests, because in Malaysia the condenser is fighting hot air all year round.

Malaysia recognised this problem on the water-cooled side and did something about it. MS 1525:2019 introduced MPLV — Malaysia Part Load Value — a weighted part-load efficiency calculated at Malaysian rating conditions. Where the AHRI IPLV lets entering condenser water temperature fall linearly from 29.4°C at 100% load to 18.33°C at 50%, MPLV uses 30.55°C at 100% falling to 26.67°C at 50% and held there below that, on the reasoning that a cooling tower in a tropical climate simply cannot deliver 18.33°C condenser water. MPLV is, in effect, an NPLV computed at Malaysian conditions.

Note that MPLV as documented in the published literature is defined in terms of entering condenser water temperature, which makes it directly a water-cooled metric. If you are specifying air-cooled equipment, check what MS 1525:2019 sets out for air-cooled part-load rating in your edition of the standard, and in the meantime apply the same logic yourself:

Ask the manufacturer for NPLV at your site’s actual ambient profile, not IPLV. Any competent chiller supplier can produce part-load data at nominated ambient temperatures. Specify the ambient bins you actually experience — something in the region of 32 to 35°C for daytime operation rather than 12.8°C — and compare tenders on that basis. This single request will change which machine wins more often than any other line in your specification.

One further data point worth knowing: an analysis of Malaysian chiller selection published through ASHRAE Indonesia found that the MS 1525 full-load COP minimum is roughly 5 to 6% more demanding than the ASHRAE 90.1 Path A constant-speed minimum at Malaysian rating conditions. If someone hands you a chiller selected against ASHRAE 90.1 and claims it therefore satisfies MS 1525, that claim needs checking rather than accepting.

How to check the chiller you already own

Compliance for new equipment is a paperwork exercise. Assessing an existing machine is a measurement exercise, and the two get confused.

Step one: find the original selection sheet. Not the nameplate — the selection sheet from when the chiller was bought, showing rated capacity, rated power, and the conditions those were quoted at. The nameplate gives you electrical data, not performance. If the selection sheet is lost, the manufacturer can usually retrieve it from the serial number.

Step two: measure what it does now. You need three things: chilled water flow, temperature difference across the evaporator, and electrical power input.

Cooling delivered: Q (kW) = flow (L/s) × 4.18 × ΔT (°C)

Convert to tons: RT = Q ÷ 3.517

Then: kW/RT = measured electrical input (kW) ÷ RT

Worked through: 40 L/s at a 5°C temperature difference gives 836 kW, or 238 RT. If the chiller is drawing 260 kW at that moment, it is running at 1.09 kW/RT, a COP of about 3.2.

Two cautions. Measure power at the chiller’s own supply with a true-RMS meter or logger, capturing compressors, condenser fans and controls — not an estimate from nameplate amps. And take the reading at a steady, reasonably high load with recorded ambient temperature, because a part-load reading compared against a full-load rating tells you nothing.

Step three: compare against the original selection first, not against the standard. This is the step people skip, and it changes the diagnosis entirely.

If the machine was selected at 1.05 kW/RT and now measures 1.30 kW/RT at comparable conditions, you do not have a compliance problem. You have a fouled condenser coil, a refrigerant charge issue, failing compressor valves, or restricted airflow — and probably a cheap fix. Published maintenance literature gives a sense of the scale: a centrifugal chiller rated at 0.50 kW/ton when new might reasonably be at 0.55 to 0.60 after five years of good maintenance, but neglected can reach 0.90 to 1.0 — which is 20 to 25% more energy for the same cooling.

Only once you know the gap between rated and actual should you ask the second question: how does the rated figure compare with today’s minimum?

Step four: compare the rated figure against MS 1525:2019. Look up your equipment type and size category in the standard’s chiller table and compare like with like — full load against full load, at matched conditions. For reference, air-cooled machines sit well behind water-cooled ones on paper; AMCON’s own published figures put typical air-cooled consumption around 1.1 kW/ton against roughly 0.75 kW/ton for water-cooled. That gap is inherent to rejecting heat into dry-bulb air rather than to wet-bulb-cooled water, and it is why the standard sets different minimums for the two.

Reading your result

The rebate window, and why timing matters

SEDA’s NUR:CHILLER programme sits under NUR@PETRA and pays industrial and commercial users to replace inefficient chillers. The published rebate rate is RM250 per refrigeration ton, and the programme runs from 1 March 2025 to 31 December 2026.

The per-applicant cap needs checking directly with SEDA before you build a business case. The programme guideline document describes a cap of 300 RT per applicant, which at RM250/RT works out to RM75,000, and an early Bernama report cited up to RM75,000. SEDA’s current programme page states a figure of up to RM500,000. Those are not reconcilable from public sources, so confirm the applicable cap for your application rather than relying on either number.

What is consistent across the documentation is the compliance chain, and it is more demanding than most applicants expect:

• The replacement chiller must meet the minimum kW/TR in MS 1525:2019
• Every new chiller must be tested at 100% load at the manufacturer’s recognised testing facility, with the factory performance test report submitted
• Every new chiller must also be tested on site at a minimum of 70% load by the contractor or supplier together with a SEDA-appointed verifier
• Chiller performance data as selected must be inscribed on a metal plate fixed to the chiller body
• The existing chiller’s efficiency in kW/RT must be verified on site before replacement
• Installation must be completed within six months of the approval letter
• The application is for comfort cooling, as part of an operational ACMV system

That last requirement about verifying the existing chiller matters for sequencing. If you are considering this, measure and document your current machine’s performance before you do anything else — including before any remedial cleaning, which will improve the baseline you are measured against.

With roughly five months left in the programme as it currently stands, and a six-month installation window attached to approval, the timeline is tight. Confirm current terms with SEDA directly.

What to do this month

If you own air-cooled chillers in a Malaysian facility and you want a defensible answer to the compliance question:

1. Retrieve the original selection sheets. Chase the manufacturer if they are missing.
2. Measure actual kW/RT at a steady, high load, with ambient temperature recorded.
3. Work out the gap between rated and actual. That number is your maintenance opportunity.
4. Compare the rated figure against MS 1525:2019 for your equipment type and size band. That number is your replacement question.
5. If replacement looks likely and the application is comfort cooling, check NUR:CHILLER eligibility now rather than after the window closes.
6. On any new tender, specify part-load data at Malaysian ambient conditions. Do not accept IPLV as the comparison basis.

Most facilities that go through this find the answer is maintenance rather than capital. The ones that genuinely need new plant find out with enough evidence to justify the spend — which is a considerably better position than replacing a chiller because someone said it did not comply.