How Much It Costs to Run Your Aircon Per Hour in Singapore

The electricity cost per hour depends on three things: the unit's power draw (in watts or kilowatts), the current electricity tariff, and how hard the compressor is actually working. An inverter unit does not run at full power continuously — it ramps down once the room reaches the set temperature and then cycles at a lower draw to maintain it. A non-inverter unit runs at full power until the room is cold, shuts off, then restarts at full power when the temperature rises.

This is why the sticker wattage overstates real-world cost for inverter units and understates it for non-inverter units in poorly insulated rooms. The sticker tells you the maximum draw. The actual draw depends on how much work the unit has to do to keep the room at the set temperature.

The electricity tariff in Singapore sits around $0.30 to $0.32 per kWh depending on the quarter. This is the multiplier that turns power draw into money. A unit drawing 1 kW for an hour at $0.31 per kWh costs $0.31. A unit drawing 0.6 kW at steady state — common for a properly sized inverter unit in a well-insulated room — costs roughly $0.19 for that same hour.

For a standard HDB bedroom with a 9,000 BTU inverter unit running at steady state, the cost per hour sits in the range of $0.15 to $0.25. The lower end assumes good insulation, a north-facing wall, and the unit cycling at low compressor speed after the initial cooldown. The higher end assumes a west-facing room, afternoon sun, or a door left open.

A living room with an 18,000 BTU or 24,000 BTU unit draws more power. Running cost per hour typically falls between $0.30 and $0.55, depending on room size, glass area, and how many people are in the space. Larger rooms with floor-to-ceiling glass in condos sit toward the higher end.

These figures assume an inverter unit in reasonable condition — clean filters, no refrigerant loss, and a condenser that is not choked with dust. A neglected unit draws more power to achieve the same cooling because the compressor runs harder and longer to compensate for restricted airflow or low gas.

An undersized unit is the most common hidden cost driver. If the unit is too small for the room, the compressor never ramps down — it runs at full power continuously, trying to reach a temperature it cannot achieve. The room stays warmer than the set point, and the electricity bill reflects a unit running flat out all day.

A dirty evaporator coil or clogged filter has the same effect. The unit is the right size on paper, but the effective cooling capacity is reduced by the buildup. The compressor compensates by running longer and harder. A chemical wash that restores coil efficiency can drop the running cost meaningfully — not by changing the unit, but by letting it work the way it was designed to.

Thermostat setting matters more than most people realise. Every degree below 24°C increases energy draw. Running at 18°C does not cool the room twice as fast — it forces the compressor to run at higher capacity for longer to reach and hold a temperature that is well below the natural equilibrium of the space. Setting the thermostat to 24–25°C and using a fan for air movement is the most efficient combination for comfort in Singapore.

Inverter units adjust compressor speed to match the cooling demand. Once the room reaches the set temperature, the compressor drops to a low speed and holds there — drawing a fraction of its rated power. This is where the energy saving comes from. The longer the unit runs per session, the more the inverter advantage shows up in the bill.

Non-inverter units run at one speed — full. They cool the room, shut off, wait for the temperature to rise, then restart at full power. Each restart draws a surge of current. In a room that is well-insulated and holds temperature, the difference is moderate. In a room with poor insulation, open doors, or heavy sun exposure — where the temperature rises quickly after the unit shuts off — the non-inverter restarts frequently, and the running cost climbs.

For most Singapore households running the aircon for several hours daily, the inverter premium pays for itself within the first few years through lower monthly bills. The gap is largest for units that run long hours — overnight in bedrooms or through the workday in a home office.

A well-maintained unit uses less electricity to do the same job. Clean filters allow full airflow across the evaporator coil. A clean coil transfers heat efficiently. A clean condenser outside rejects that heat without the compressor straining. Each of these factors reduces the time and power the compressor needs to hold the set temperature.

The compounding effect of skipped maintenance is what catches homeowners off guard. A slightly dirty filter alone might add a small percentage to the bill. Combined with a coil that has not been chemically washed, a condenser gathering dust, and refrigerant that has dropped slightly from a slow leak — the total running cost can be noticeably higher than the same unit in clean condition.

Regular servicing is not just about preventing breakdowns. It is about keeping the unit running at the efficiency it was rated for. The electricity savings from proper maintenance often cover the cost of the service visits themselves.