In Singapore’s heat and humidity, air-conditioning is practically a daily essential. Whether you have just collected the keys to your new apartment or are thinking about replacing an ageing system, choosing and using the right setup can make a significant difference to your comfort, electricity bills, and long-term maintenance costs.

But many households still end up overcooling rooms, wasting energy, or overlooking simple habits that help systems run more efficiently. From learning the best temperature settings to deciding how many units your new home needs, there are several smart ways to optimise your cooling effort.

You want your apartment to be cool when you get home

Activate the air-conditioner via a smart home app about 15 to 30 minutes before you arrive, advises one industry expert. The recommended setting? A temperature of 25°C with a medium-speed fan.

Pre-cool only the rooms you will use immediately — typically the living room and bedroom. Cooling unused rooms adds to the bill without improving comfort. For homes not linked to an app, set the air-conditioner at 23°C or 24°C for about 10 to 15 minutes for a quick initial cool-down, then return to 25°C. Avoid using 18°C — it does not cool the interior faster. Most units cool at a similar rate; they just run longer and cost more to reach a lower setpoint.

To feel cooler without dropping the thermostat, switch on a ceiling or standing fan at the same time. Once the room is comfortable, you can even raise the temperature to 26°C and continue using an external fan for air movement. Keep doors and windows closed, and draw curtains — especially in rooms with west-facing sun.

To prepare your bedroom for sleep, close blackout curtains around 5pm or 6pm if the room faces west. Before bed, set the temperature at 25°C with a fan, rather than 22°C all night. Use the sleep or econ mode — these settings typically ease the compressor load after the initial cool-down.

You do not want the bills to burn a hole in your pocket

Most people know about the energy efficiency rating that awards appliances one to five ticks — the higher the number, the more efficient the model. But how does that translate into dollars?

For example, cooling a typical HDB bedroom with a split-inverter air-conditioner for eight hours often uses around 4kWh to 8kWh. At Singapore's household electricity tariff (about 30 cents per kWh), that costs about S$1.20 to S$2.40 per night, or S$36 to S$72 a month.

If a model uses 150kWh less per year than another, that saves about S$45 annually — before considering differences in usage patterns. Use the timer or sleep mode to avoid running at full load in the early morning when the room is already cool. Many households see a noticeable drop in bills by moving from 22°C to 25°C with a fan and a two-to-three-hour timer — comfort levels are similar, but the compressor cycles less. Other practical methods include closing doors, sealing gaps under them, and cleaning filters regularly.

You want your home to smell clean and fresh

The air-conditioner itself does not produce pollutants, but it can trap and recirculate what is already indoors — fine dust, cooking fumes, pet dander, and volatile organic compounds from new furniture, paint, and cleaning agents.

The musty odour you notice when the air-conditioner is switched on is caused by a combination of moisture and trapped dust, skin flakes, and cooking aerosols settling on cooling coils and nearby fabrics. Even a newly renovated flat can have lingering odours if the air-conditioner runs 24/7 with windows closed.

A quick way to minimise odour and moisture — without expensive cleaning — is to ventilate your apartment daily. Open windows for 10 to 15 minutes in the morning when the air outside is cooler. Avoid overcooling or using very low setpoints, as this can make surfaces cold enough for condensation to form when someone opens the door. Use a fan to keep air moving, especially in stagnant corners. Ensure condensate drainage is working — a slow drain leaves the unit wetter.

If your unit has a coil-dry or mould-proof function, use it. Otherwise, run fan-only mode for 10 to 20 minutes before switching off to dry internal moisture. Other quick tips: do not dry wet laundry in the room when the air-conditioner is on, and keep filters clean so the system dehumidifies efficiently.

You do not want to overspend on maintenance

For most households, regular servicing and filter washing are enough. Washing filters yourself is recommended, but it does not fully replace professional cleaning. Filters mainly catch larger dust particles, but fine particles and oily residue — especially in homes that cook often — build up on the coil, fan, and drainage system. When these parts are dirty, you can experience weaker airflow, higher energy use, odours, or water leakage — even when filters look clean.

Chemical cleaning should be reserved for specific problems: weak airflow, persistent odour, water leakage, or a heavily clogged coil. It uses specialised solutions to break down stubborn grime on internal components like the evaporator coil, blower wheel, and drainage tray — areas simple wiping cannot reach.

Schedule routine servicing every three to six months — more regularly if you use the system daily, have pets, or live near construction. Get the outdoor condenser checked and cleaned about once a year — or sooner if exposed to dust, leaves, or lint. Call for chemical cleaning only when signs appear, or when a technician recommends it. Alternatively, greener methods like steam cleaning are also available.

You want to optimise your home's air-conditioning system

Consider replacement when you see a pattern of frequent faults, weak cooling despite proper servicing, unusual noise, recurring water leakage, or rising electricity bills for the same usage. In Singapore's daily-use reality, many residential split systems last around eight to 12 years with reasonable maintenance. Heavy use, poor ventilation around the condenser, or chronic dirt build-up can shorten that.

Replace the most-used rooms first, such as bedrooms — that is where you will feel savings and comfort improvement fastest. Compatibility matters. If you are on a multi-split system, replacing only some indoor units may not make sense unless the outdoor unit and refrigerant system are compatible with new indoor models. A technician should confirm what can be mixed safely.

If you have just received keys to a new apartment, consider how you will use the cooling system. "Right-size" rather than add more units after moving in. Think about which rooms require regular cooling, and consider their size and heat load — is there a west sun, large windows, or high ceilings? Will rooms be kept closed? Do you plan to convert a room into a baby's room or a work-from-home space in the future? Planning ahead saves money and avoids mismatched systems down the road.