It is April in Bangkok, the aircon has run all day in a flat that was empty from 8 a.m., and the electricity bill shows it. Aircon is usually the single biggest load you can control in a Thai home. It is also the one most often left running by habit rather than need.
This guide is about automating it sensibly: what to switch on and off, how to deal with the hot season, how to zone rooms, why humidity matters and why a dirty unit undoes some of your good work. There are no invented savings percentages here. Your bill depends on your unit, your room and your life, and the honest way to know is to measure it.
What smart aircon control actually does
Smart control does not make the compressor more efficient. It changes when the unit runs, what it is told to do and who decides. Three layers cover most homes:
- Remote control. From your phone, from anywhere. Useful for the "did I leave it on?" moment.
- Schedules. The unit follows times you set, such as cooling the bedroom before bed and relaxing the setpoint overnight.
- Triggers. The unit reacts to something: the last person leaving, a door opening, the room getting too humid.
Most of the value is in the third layer. A schedule assumes your life is regular. A trigger responds to what is actually happening.
How to connect an existing unit
You have three realistic routes.
- Infrared controller. A small box learns the commands from your remote and sends them on demand. It works with most split units and does not modify the aircon. This is the most flexible option for a condo or a rental.
- Built-in wifi unit. Some newer units connect directly to an app or a smart-home hub. Convenient, but you are tied to what the manufacturer allows.
- Thermostat or controller wired in. Common with ducted or central systems, and not appropriate for renters. It needs an electrician and the owner's permission.
Avoid the shortcut of cutting power to a split unit with a smart plug. Many units forget their settings or restart in an unexpected mode, and repeated hard power cuts are not what the equipment was designed for. Send the unit commands instead.
If you rent a condo, read our guide to a smart home in a Bangkok condo, which covers permission and reversible installs.
Automation 1: switch off when everyone leaves
This is the highest-value rule, and it takes a few minutes to set up. The logic:
- Detect that the home is empty. Use phone location for each person, a front-door sensor, or a motion sensor, ideally two of these.
- Wait a sensible delay, such as fifteen minutes, so a trip to the 7-Eleven downstairs does not switch things off.
- Switch the aircon off, or set it to a gentle, higher setpoint if you will be back soon.
- Send a notification: "Aircon switched off, home empty."
Guard against the mistakes. If a helper or a sleeping child is in the flat, phone location alone will say the home is empty. Add a motion or door check, and make the rule skip bedrooms where someone is asleep. A rule that switches off an occupied bedroom at 2 p.m. will be turned off by the household within a week.
Automation 2: get cool before you arrive
The opposite problem is the room that is boiling when you come home, so you set the unit to 16 degrees. That habit uses more energy than needed. A better rule starts the unit shortly before arrival, at a normal setpoint, using your phone's location, or a simple time on weekdays.
A worked example for a one-bedroom condo near BTS Phrom Phong:
| Time or trigger | Action |
|---|---|
| 07:45, everyone out | Living room and bedroom units off |
| 17:30 weekdays, or phone within 2 km of home | Living room unit on at a normal setpoint |
| Door opens after 17:00 | Confirm living room unit running |
| 22:30 | Living room off, bedroom on |
| 01:00 | Bedroom setpoint up one or two degrees |
| 06:30 | Bedroom off |
The details are yours to tune. The shape of the day is what matters.
Scheduling around the hot season
Bangkok's seasons are not subtle. The hot season, roughly March to May, makes the afternoon peak long. The rainy season brings humid but milder days. The cooler months, roughly November to February, often need little cooling in the daytime but some at night.
Use this by keeping separate schedules, switched by season instead of rewritten every time:
- Hot season: start earlier, allow longer run time in the afternoon, keep curtains closed on sun-facing windows during the peak.
- Rainy season: watch humidity more than temperature.
- Cool season: many days need no daytime cooling, so let the schedule default to off and rely on fans, while keeping the night schedule.
Pair the schedule with shade. Closing curtains before the afternoon sun hits is one of the cheapest ways to reduce the load, and motorised curtains can do it automatically.
Zoning: cool the room you are in
Whole-home cooling is the most expensive way to be comfortable. In a house or a larger condo with several units, treat each room on its own:
- Bedroom: on only in the evening and overnight.
- Living room: on when someone is there, and for a while after dinner.
- Home office: on during working hours only.
- Spare room: off unless in use.
Keep doors closed to the cooled room. The same unit will not cool a living room that is open to the whole floor. A motion sensor in each room tells the system whether anybody is there, and a short timeout avoids switching off on someone who is sitting still on the sofa.
For a home office, think about the working day rather than the clock; our home-office setup work often includes this kind of room-level control.
Humidity: comfort is not just temperature
In Bangkok, a room can be 27 degrees and still feel clammy. If humidity is high, people drop the setpoint to feel better, which makes the unit work harder. Many aircon units have a dry mode that reduces humidity with less cooling, and fans help the air feel cooler at a higher temperature.
A cheap temperature and humidity sensor lets the system act on what you feel. A simple rule: if humidity stays high while the room is occupied, switch to dry mode instead of lowering the setpoint. If you cannot get the humidity down, look for the cause, such as an open balcony door, damp laundry drying indoors or a unit that is not draining properly.
Keep the unit healthy: servicing and cleaning
Automation can decide when the unit runs. It cannot fix a unit that is working badly. A dirty filter or coil restricts airflow and heat exchange, so the unit works harder to deliver the same cooling, and a blocked drain can leak water. Bangkok dust, construction and the PM2.5 season mean filters collect dirt quickly.
Two useful habits:
- Rinse the filters regularly. A monthly check is a reasonable starting point for a busy unit, but follow your manual.
- Book a professional clean on a schedule. Many households choose once or twice a year, before the hot season and perhaps after PM2.5 season.
Our sister brand CoolRova does aircon cleaning in Bangkok, and the two fit together well: automation reduces unnecessary running, and servicing keeps the running efficient. You can also automate the reminder, so the system tells you when it is time to book.
Measure before you believe anyone
Because the result depends on your home, measure it:
- Note your monthly kWh from the electricity bill for the last three to six months. In Bangkok, your bill comes from the Metropolitan Electricity Authority, and most bills show units used.
- Note the weather. A hot April and a mild January are not comparable.
- Install the automation and leave other habits alone.
- Compare against comparable months.
For better data, a smart plug with an energy meter, or a clamp meter fitted by an electrician, gives per-circuit readings. Remember that a plug with a meter is for measuring only and not for switching the unit. Be wary of any promise of a fixed percentage saving. It cannot be known without your data.
Do not automate yourself into discomfort
A few honest warnings:
- Elderly people, babies and anyone ill should not have the aircon switch off on a rule without a safety check. Heat is a real risk.
- Pets left at home need a safe temperature. Think twice before a rule that turns the unit off with them inside.
- Overrides must be easy. A button or a wall remote should always work, and the rule should back off for a while after a manual change.
- Keep the original remote as a fallback if the controller or wifi fails.
Where DigitalRova fits
We set up the hub, the controllers and the rules, and we write them so the household can understand and change them. A smart-home starter is from ฿19,900, about a day on site, excluding devices, and a whole-home project is from ฿69,000. See smart home solutions, home automation and pricing.
If you would like a plan for your home, tell us about your rooms and units and we will suggest where to start.