What Temperature Should You Set Your Air Conditioner in Cambodia?

One of the most common habits in Phnom Penh households is setting the air conditioner to 18°C or 16°C the moment you walk in from the heat and then leaving it there. It feels decisive. The room cools down. Problem solved.

Except the thermostat setting you choose has a larger effect on your electricity bill, your unit's lifespan, and the actual quality of cooling you experience than almost anything else you do with your AC. And 18°C is rarely the right answer.

How Your Thermostat Actually Works

There's a widespread misconception that setting a lower temperature cools the room faster. Your air conditioner doesn't work that way. A split-system unit operates at full cooling capacity from the moment it starts running until it reaches the set temperature — then it cycles off. Setting 16°C instead of 24°C doesn't make the unit blow colder air during the cool-down phase. It just means the unit runs for longer before it stops.

This matters because every extra hour the compressor runs is an hour of electricity consumption and an hour of wear on the most expensive component in the system. A thermostat set to 16°C in a Cambodian apartment in March may mean the compressor never cycles off at all — the unit simply can't overcome the heat load to reach that temperature, so it runs continuously.

The result: higher electricity bills, faster component wear, and in many cases, a room that actually feels less comfortable, not more. A room chilled to 18°C in Phnom Penh's humidity often feels simultaneously cold and clammy — the AC is running cold but the humidity isn't being managed as effectively as it would be at a higher, more sustainable set point.

What Temperature Is Actually Comfortable in Cambodia?

For most people in Phnom Penh, 24–26°C is the sweet spot.

At this range, a properly functioning split-system unit will:

• Cycle on and off naturally rather than running continuously
• Remove humidity from the air effectively, which is often more important than raw temperature
• Maintain comfortable conditions without the clammy overcooling effect
• Consume significantly less electricity than at lower settings

The commonly cited benchmark is roughly 6–8% additional electricity consumption per degree below this range. Dropping from 26°C to 18°C — a seemingly obvious choice when you've just walked in from 38°C heat — represents something like a 50–60% increase in running costs, and likely more on a unit that's already working hard in a hot apartment.

The reason 24–26°C feels genuinely cool in Phnom Penh, where outdoor temperatures regularly reach 35–38°C, is the contrast effect. Coming in from the heat, any indoor temperature below ambient feels pleasant quickly. The discomfort people associate with "not cold enough" is usually the adjustment period — which passes within a few minutes regardless of what the thermostat is set to.

The Humidity Factor

Cambodia's climate makes humidity management as important as temperature, and this is where thermostat settings interact with AC performance in a way that surprises most people.

Air conditioners remove humidity as a natural consequence of cooling — warm, humid air passes over the cold evaporator coil, moisture condenses on the coil surface and drains away, and drier air returns to the room. This dehumidification effect is what makes air-conditioned rooms feel genuinely comfortable rather than just cooler.

When you set the thermostat too low and the unit never reaches its target temperature — running continuously at full capacity — the coil stays extremely cold. This can actually cause issues with ice formation on the coil surface, which paradoxically reduces the unit's ability to dehumidify. A cycling unit set at 25°C often achieves better practical comfort than a non-cycling unit set at 18°C, because the room is drier at a moderate temperature rather than humid at a very cold one.

If you have a unit with a dry mode or dehumidify mode, using it during Phnom Penh's rainy season can manage moisture more effectively than aggressive cooling — particularly in the early evening when humidity peaks.

Overnight Settings

Most people sleep best at temperatures between 20–22°C — cooler than daytime comfort but not cold. In Phnom Penh's climate, an overnight setting of 23–25°C typically achieves this, especially once you factor in bed linen.

The practical approach that works well for most households: set the unit to your comfortable daytime temperature for the first hour or so after going to bed, then use the timer to shift to a slightly warmer setting — 26°C — for the remainder of the night. Your body temperature drops naturally during sleep, and many people find they actually sleep better at a slightly warmer setting than they'd expect.

Alternatively, a timer set to switch the AC off entirely after three to four hours works for households that prefer to sleep in natural overnight temperatures. Phnom Penh nights during the cooler months (November–February) are often manageable without continuous AC after the initial cool-down period.

What doesn't work well: setting the AC to 18°C and sleeping under a thick duvet. This is a common pattern that wastes electricity, stresses the compressor, and contributes to the rapid mould growth inside units that run very cold in humid environments — as the temperature differential between the coil and the room air becomes extreme.

How Thermostat Settings Affect Your Unit's Health

The connection between thermostat habits and unit longevity isn't immediately obvious, but it's real and significant.

A compressor that's running continuously — because the set temperature is unreachably low — is generating heat internally and accumulating wear at a rate it wasn't designed for. Lubricants in the compressor degrade faster at sustained high temperatures. Seals wear more quickly. The thermal cycling stress that the unit is designed to manage (on-off-on-off) is replaced by sustained stress. Over time, this is one of the patterns that shortens a unit's working life from the fifteen years it's capable of to seven or eight.

The guide to extending your air conditioner's lifespan in Cambodia covers this in more detail — thermostat habits are listed alongside maintenance schedule as one of the highest-impact factors in determining how long your unit lasts. A unit running at 24°C, cycling naturally, is genuinely aging more slowly than the same unit set to 18°C and running continuously.

Mould prevention is also affected. Evaporator coils running at extreme cold accumulate more frost and condensate, which combined with dust buildup creates more favourable conditions for biological growth. Moderating the temperature — keeping the coil from running far colder than necessary — is a minor but real factor in slowing the rate of mould establishment.

What This Means for Your Electricity Bill

The energy saving tips for air conditioners in Cambodia frame this clearly: thermostat management is the second most impactful thing you can do for electricity consumption, after keeping your unit properly cleaned.

On a typical Phnom Penh inverter split running ten hours per day, moving from an average thermostat setting of 20°C to 25°C can reduce electricity consumption by 25–35% — a meaningful reduction in monthly bills at Cambodia's electricity rates. The exact saving depends on the unit, the room size, insulation, and ambient temperature, but the direction is consistent and the magnitude is substantial.

The practical scenario that illustrates this best: two identical apartments, identical units. One household sets the thermostat at 24°C consistently; the other defaults to 18°C. Over a year, the difference in electricity bills is significant. Over five years, the difference in compressor wear is also significant. The same habits that save money monthly are also the ones that delay the eventual cost of a major repair or replacement.

A Simple Approach for Most People

If you're looking for a starting point rather than a comprehensive optimisation:

• Daytime cooling: 24–26°C, adjusted to what feels comfortable once you've been indoors for ten minutes
• Sleeping: 23–25°C, or use a timer to shift warmer after the first hour or two
• Coming in from extreme heat: Resist the impulse to set the thermostat low. The room will cool down at the same rate regardless.
• Dry season midday: If the room is already getting down to temperature quickly, raising the setting slightly preserves comfort while running the unit less

The underlying principle is to let the unit cycle naturally — reaching its set temperature and switching off — rather than running continuously. A unit that cycles properly is doing its job correctly. A unit that never cycles off is struggling, costing more to run, and wearing out faster.

This is one reason why keeping your AC well maintained is closely linked to achieving comfortable temperatures at moderate thermostat settings. A clean evaporator coil transfers heat efficiently, reaching the set temperature with less effort. A coil coated in dust and biological buildup works harder for the same result — which pushes people to lower the thermostat further to compensate, creating a cycle of increasing electricity consumption and faster degradation.

The benefits of regular AC cleaning include improved efficiency — but in practical terms, what this often means for residents is that a well-maintained unit feels comfortable at 25°C, while a dirty one feels inadequate at 22°C. The difference isn't the thermostat. It's the coil.

Set your thermostat at 24–26°C. Keep the unit clean. The combination is more comfortable and substantially cheaper than the alternative.