Aircon systems in Singapore: System 1 to 4, inverter, cassette and ducted compared

NEA raised the Minimum Energy Performance Standard (MEPS) for single-split air-conditioners to 4 ticks from 1 April 2025, so new models supplied from that date must be at least 4-tick. NEA's release notes that products supplied to the market before the effective date are exempted, so check the tick rating on the label in the shop.

In HDB flats, outdoor units sit on the air-conditioner ledge where there is one, or at an approved location for flats without a ledge. HDB's guidelines for flats with a 40A main switch allow a maximum of two split-type condensing units, with a weight limit of 110 kg per wall panel and one wall-mounted condensing unit per wall panel. That is why many HDB owners combine a System 1 with a multi-split, or use one large multi-split.

From 1 April 2025, NEA raised MEPS for multi-split air-conditioners to 5 ticks, the highest rating. Multi-split inverter units are rated on a weighted COP that combines full-load and half-load performance, which reflects how inverter units actually run at home.

A System 3 commonly covers the bedrooms of a 3-room or 4-room flat, or two bedrooms plus the living room. Plan the indoor unit positions with your carpentry and false ceiling, so piping can run internally (an HDB requirement) and trunking or ceiling boxes can hide it. Ask your installer to confirm the total running current and weight against HDB's limits for your flat.

A System 4 is popular because it fits the cooling of a whole family flat into one outdoor unit. Before committing, check three things with your installer and electrician:

• Weight and location: the condensing unit must suit your ledge or approved location; HDB sets a limit of 110 kg per wall panel for flats with a 40A main switch.
• Electrical supply: HDB says the running current should be restricted by a 20A double pole isolator or 15A power point, and new wiring must be done by an EMA licensed electrical worker.
• Pipe lengths: long runs to far rooms reduce efficiency and must stay within the manufacturer's limits.

If you only use two rooms most nights, compare the cost of a System 3 plus a System 1 for the living room, which keeps one room running if the other system fails.

An inverter unit varies its compressor speed to hold the set temperature, so it runs efficiently at part load. A non-inverter unit runs at full speed, switches off when the room is cool, then switches on again. NEA's MEPS table sets the same minimum figure for single-split inverter (weighted COP) and non-inverter (full-load COP) units from April 2025, but because homes rarely need full cooling for long, inverter units usually suit long hours of use better.

For bedrooms used all night, an inverter unit is the usual recommendation. Always compare the tick rating and the estimated annual energy cost on the NEA label rather than the inverter label alone.

Cassettes need ceiling space for the unit body, piping and condensate drainage, so they are planned with the false ceiling rather than added later. Ask the installer for the required ceiling void, the position of access panels and how condensate will drain. HDB requires condensation water to be discharged into a floor trap in your flat.

Cassettes are less common in HDB flats because of ceiling height and the cost of a full false ceiling. In condos, check the developer's provisions and your MCST's by-laws on outdoor unit locations before choosing.

Ducted systems need careful design: the indoor unit size, duct routes, return air path and access panels for servicing. A poorly designed system can be noisy or leave rooms unevenly cooled. Ask who designs the ductwork and for drawings showing access panels.

Because ducts and filters collect dust and can harbour mould in humid conditions, plan regular servicing and easy access. Ducted units suit Luxury and Minimalist interiors where visible units would spoil the look.

NEA raised MEPS for casement and window units to 2 ticks from 1 January 2022. These units are less efficient than modern split systems, so compare the estimated annual energy cost on the label before buying.

HDB's guidelines cover window units as well as split units: they must be installed at approved locations and by approved methods, cannot be placed along the common corridor, and must not cause vibration. Check with your HDB Branch if you are unsure about an existing opening. Many owners renovating older flats replace window units with split systems.

NEA introduced energy labelling and minimum standards for portable air-conditioners from 1 April 2024. Their efficiency thresholds are far lower than for split systems, which reflects how much less efficient they are.

Use a portable unit as a temporary solution, for example in a rental where you cannot install a split system, or in a room while waiting for renovation. Seal the window gap around the hose as well as you can, and empty or drain condensate as the manual says.

NEA regulates three-phase VRF air-conditioners under its labelling and MEPS scheme, with a rating based on an integrated efficiency measure. These systems are designed by specialist contractors, so ask for a load calculation, a piping and wiring layout, and the maintenance plan.

VRF makes sense when a landed home has many rooms to cool and limited space for outdoor units. Electrical works for the three-phase supply must be designed and carried out by a licensed electrical worker.

NEA has encouraged households to set air-conditioners to 25°C or higher to save energy. A ceiling fan makes that setting feel cooler, and on drier evenings may be enough on its own. Direct current (DC) fans are among the product types eligible for Climate Vouchers, and fans must carry the SAFETY Mark to be sold in Singapore.

Plan fan points at the same time as your aircon and lighting, so the fan does not sit right under a downlight or blow directly into an air-conditioner. See our lighting guide for fans with lights.