System 2, 3 or 4 — which do I need?

The number is how many indoor fan coils run off one outdoor compressor. System 3 (three rooms) is the most popular for HDB flats; System 4 if you need to cool four rooms.

What BTU size for each room?

Roughly 9,000 BTU for a common bedroom, 12,000 BTU for a master bedroom, and 18,000–24,000 BTU for an HDB living room.

How much does installation cost?

Standard wall-mounted install is about S$120–S$400 per indoor unit; multi-split installation runs higher. The unit itself (5-tick System 3) is typically S$2,600–S$3,600.

Buying Aircon for an HDB Flat: Types, Sizing & Install Costs (2026)

Buying aircon in Singapore comes down to three questions: how many rooms you need to cool, what size each unit should be, and which efficiency tier to choose. Get those right and you’ll have a system that cools well, doesn’t wreck your electricity bill, and meets the current rules. Here’s the full guide.

How many rooms? (System 2, 3 or 4)

The “System” number is how many indoor fan coils connect to one outdoor compressor. System 3 — one compressor serving your living room plus two bedrooms — is the most popular choice for HDB flats and condos, because it matches the typical layout. Go System 2 for a smaller home where you only need to cool two rooms, or System 4 if you need four rooms cooled. Choosing the right number avoids paying for capacity you won’t use, or running short.

What size? (BTU by room)

Each indoor unit is sized in BTU to the room it cools. As a guide:

Common bedroom (80–120 sqft): ~9,000 BTU
Master bedroom (120–180 sqft): ~12,000 BTU
HDB living room: 18,000–24,000 BTU

Under-size the unit and it runs constantly without ever cooling properly; over-size it and you waste money and get poor humidity control. A reputable installer will size each fan coil to the room.

Efficiency tiers and the 2025 rule

Appliances carry an energy tick rating — more ticks means more efficient and lower running costs. Importantly, since 1 April 2025 the NEA raised minimum energy standards, and the old budget 2-tick and 3-tick multi-split systems can no longer be sold for new installations. You’ll now be choosing between 4- and 5-tick units, which cost more upfront but cut your electricity bill over the years you own them. Government Climate Vouchers can offset part of the cost for eligible HDB households — worth checking before you buy.

What it costs

A 5-tick System 3 from a trusted brand typically runs S$2,600–S$3,600 for the unit alone. On top, budget for installation: roughly S$120–S$400 per indoor unit for standard wall-mounted work, more for multi-split runs with longer piping. All in, a full System 3 supply-and-install often lands somewhere in the low-to-mid thousands depending on brand, tier and installation complexity. Get itemised quotes so you can compare the unit price and the installation separately.

Choosing an installer

The installation matters as much as the unit — poor piping, drainage or bracket work causes leaks and inefficiency down the line. Use an experienced, reputable installer, get more than one quote, and confirm what’s included (piping length, brackets, trunking, disposal of the old unit). Ask about the workmanship warranty as well as the manufacturer warranty. In a rental, check who’s paying — a new system is usually the landlord’s decision and cost.

Running it efficiently

Once installed, a few habits keep the bill down: set it to around 25°C and pair it with a fan, use the timer overnight, close doors and curtains, and keep it serviced. Cooling is the biggest single item on most Singapore electricity bills, so how you run the aircon matters — see our guide to cutting your electricity bill.

Servicing keeps it healthy

A new system needs regular upkeep to stay efficient and last: a general service every few months and a chemical wash roughly yearly. Neglect it and it cools weakly, smells musty, or drips. Our aircon servicing guide covers how often and what it should cost.

The bottom line

For most HDB flats, a 5-tick System 3, correctly sized (9,000 BTU common rooms, 12,000 master, 18,000–24,000 living room), professionally installed, is the sensible buy. Expect the unit around S$2,600–S$3,600 plus installation, use any Climate Voucher you’re eligible for, and choose your installer as carefully as your unit. Then run it at 25°C with a fan and keep it serviced, and it’ll cool your home well for years without a shocking bill.

Inverter technology and why it matters

Modern aircon units are almost all inverter models, which vary the compressor speed to hold a steady temperature rather than switching fully on and off. The practical benefits are lower running costs, quieter operation and more stable comfort — worth having, and standard on the higher-tick units you’ll be buying under the current rules. When comparing units, focus on the tick rating (efficiency), the BTU sizing for your rooms, and the brand’s reliability and after-sales support, rather than a long list of secondary features you may never use.

Placement and installation quality

Where the indoor units and the outdoor compressor go affects both performance and your comfort. Indoor units should be positioned to circulate air well without blowing directly on the bed; the outdoor compressor needs proper ventilation on the aircon ledge. Good installation — correct piping gradient for drainage, secure brackets, neat trunking — prevents the leaks and inefficiency that plague badly-installed systems. This is why the installer matters as much as the unit: a cheap install on a good unit can cost you more in problems than you saved.

Warranty and after-sales

Check both the manufacturer warranty (on the unit and compressor) and the installer’s workmanship warranty before buying. Aircon is a multi-year purchase, and good after-sales support — for servicing, parts and any warranty claims — is worth paying a little more for. Keep your purchase and installation documents, and start a regular servicing schedule from the outset to keep the warranty valid and the system efficient. Buy the right size and tier, install it well, and maintain it, and a good aircon system will cool your home reliably for a decade or more.

A quick buyer’s summary

To boil it down: pick the system size by how many rooms you need to cool (System 3 for most HDB flats), size each fan coil to its room (about 9,000 BTU for a common bedroom, 12,000 for a master, and 18,000–24,000 for a living room), and choose a 4- or 5-tick unit as required under the current rules. Budget roughly S$2,600–S$3,600 for the unit plus installation, use any Climate Voucher you qualify for, and choose an experienced installer as carefully as you choose the unit — good installation prevents the leaks and inefficiency that plague cheap jobs. Confirm both the manufacturer and workmanship warranties, then run the system efficiently and keep it serviced. Get that combination right and your aircon will cool your home reliably for years without a shocking electricity bill or premature breakdowns. Compare itemised supply-and-install quotes so you can see exactly what you’re paying for the unit versus the installation.