Surviving Heat Waves: Fans, Window Films, and Power-Saving AC Settings
Last July, I walked into my apartment after a weekend trip and was hit by what felt like an actual wall of heat. The sun had been beating directly onto my south-facing windows for three days straight, and the indoor temperature gauge read 34°C. My first instinct was to crank the AC to its coldest setting, but then I glanced at last month's electricity bill—over ₩180,000—and reconsidered. That moment made me realize I needed a better strategy than just "turn everything on and hope for the best."
Heat waves in Korea have been getting longer and more intense, especially in cities where concrete and asphalt trap heat overnight. With progressive electricity pricing (where your rate jumps dramatically once you pass certain usage thresholds), keeping cool without breaking the bank requires some actual planning. What surprised me most, though, was how much difference small changes made—things that had nothing to do with running the AC 24/7.
Table of Contents
Why Korean summers hit differently
If you've experienced summer anywhere else and thought you were prepared for Korea, the humidity here will teach you otherwise. It's not just that temperatures reach the mid-30s—it's that the humidity often sits above 70%, making the "feels-like" temperature significantly higher. This combination makes sweat less effective at cooling you down, which is why even sitting still can feel exhausting during peak summer.
Korean apartments add their own challenges. Most buildings have large windows (great for light, terrible for heat gain) and concrete construction that absorbs heat during the day and radiates it at night. If you're on a higher floor facing south or west, your place essentially becomes a solar collector. The thermal mass of all that concrete means that even after the sun sets, your walls are still releasing stored heat into your living space.
What caught me off guard my first summer here was the concept of "tropical nights" (열대야)—when the temperature doesn't drop below 25°C even at night. These aren't occasional events; during July and August, Seoul can have 10-15 consecutive tropical nights. Your apartment never gets a chance to cool down naturally, which makes the next day even harder to manage.
Personal observation: I used to think opening windows at night would help, but during tropical nights, you're often just letting in hot, humid air. The strategy needs to be more selective than "just open everything."
Choosing and positioning fans effectively
Not all fans serve the same purpose, and this is where I see people waste money buying the wrong type. A standing fan might look sleek, but if you're trying to move air across your entire apartment, a box fan or a circulation fan (서큘레이터) will do far more work. Circulation fans aren't designed to blow on you directly—they're designed to keep air moving throughout a space, which matters more than you'd think when you're running an AC.
Here's what actually works: position a circulation fan to blow air toward your AC unit's output. This sounds counterintuitive, but what you're doing is helping distribute the cold air before it just pools on the floor near the unit. Cold air is heavy and sinks, so without help, your AC cools the bottom third of your room beautifully while the upper two-thirds stay warm. The fan breaks up that stratification.
If you don't have AC or you're trying to extend the time before you need to turn it on, create cross-ventilation with two fans. Put one fan facing outward at a window on the hot side of your apartment (usually south or west), and another facing inward at a window on the opposite side. This creates a pressure difference that pulls air through your space. It won't cool things down, but it will make the existing temperature more bearable by keeping air moving across your skin.
Fan types and their actual uses
- Standing/tower fans: Good for direct personal cooling while sitting or sleeping
- Circulation fans: Best for moving air around rooms and distributing AC output
- Box fans: Effective for window exhaust or intake when creating cross-ventilation
- Ceiling fans: Useful if you have them, but rare in Korean apartments
One more thing about the Korean fan death myth (팬 데스)—yes, some older Koreans still believe running a fan in a closed room can be dangerous, which is why many fans here come with timers. While the myth isn't based on evidence, the timer feature is actually useful for another reason: it prevents you from running fans unnecessarily all night, which saves electricity without any safety concerns.
Window films that actually work
I was skeptical about window films until I measured the temperature difference myself. On a window with no treatment, the glass surface reached 48°C on a sunny afternoon. After applying a heat-blocking film, the same measurement showed 38°C. That 10-degree difference translates to significantly less heat radiating into your room, which means your AC doesn't have to work as hard to compensate.
The key is understanding what you're actually buying. Marketing terms like "heat blocking" or "UV protection" get thrown around, but what matters is the solar heat gain coefficient (SHGC). This number tells you what percentage of solar heat passes through the window. A film with an SHGC of 0.4 means 40% of solar heat gets through, while 60% is blocked. For Korean summers, look for films with SHGC values between 0.3 and 0.5—lower numbers block more heat but also reduce visible light.
You'll find two main types in Korean home stores and online: reflective films and absorptive films. Reflective films (the ones that look mirror-like from outside) are more effective at blocking heat, but they can bother neighbors in apartment complexes because of glare. I've seen management offices in some buildings ask residents to remove overly reflective films. Absorptive films are darker, less shiny, and usually more acceptable in shared buildings, though they block slightly less heat.
Common mistakes with window films
- Applying film to the outside surface (it degrades much faster from weather exposure)
- Not cleaning the glass thoroughly before application (bubbles and dust get trapped)
- Choosing films that are too dark, making rooms gloomy even during the day
- Forgetting that films can void some window warranties if not applied correctly
Application isn't complicated, but it requires patience. You'll need soapy water, a squeegee, and a razor blade for trimming. The soap allows you to slide the film into position before it sticks. Work slowly, pushing out bubbles from the center to the edges. In my experience, doing this on a cloudy day helps—direct sunlight makes the adhesive set faster, giving you less time to adjust positioning.
For renters worried about deposits, most window films are removable. They may leave some adhesive residue, but this cleans off with rubbing alcohol. I've removed films when moving out of two different apartments without any deposit deductions, though I'd recommend testing removal on a small corner first to see how your specific film behaves.
AC settings that save money without suffering
The single most expensive mistake I see people make is setting their AC to 18°C and leaving it there. This feels like it would cool the room faster, but air conditioners don't work that way—they run at basically the same cooling rate whether you set them to 18°C or 26°C. The difference is that at 18°C, the unit runs constantly trying to reach an unnecessarily low target, while at 26°C, it cycles off periodically once the target is reached.
Set your target temperature between 26°C and 28°C. I know this sounds warm, but remember that your AC is removing humidity while cooling. A 26°C room with low humidity feels significantly more comfortable than a 26°C room with high humidity. The dehumidification effect matters as much as the temperature drop, especially in Korean summers where humidity is often the bigger problem than pure heat.
Use the "energy-saving" or "power-saving" mode (절전 모드) if your unit has it. This adjusts fan speed and cycling to reduce power consumption while still maintaining temperature. The room might take slightly longer to cool initially, but the energy savings over a full day are substantial—typically 20-30% lower consumption compared to running in normal or turbo mode.
What surprised me: Running my AC at 27°C continuously used less electricity than letting the room heat up and then running it at 22°C for shorter bursts. Steady, moderate operation beats yo-yo temperature cycles.
Clean your filter every two weeks during heavy-use months. A clogged filter forces the unit to work harder, increases energy consumption, and reduces cooling effectiveness. Most Korean AC units have easily accessible filters that you can rinse under a tap—it takes five minutes and makes a noticeable difference. If you can't remember the last time you cleaned yours, do it today before you keep reading.
The "sleep mode" or "good sleep" function on many Korean AC units isn't just marketing. It gradually increases temperature by 1-2 degrees over several hours, matching your body's natural temperature drop during sleep. You stay comfortable, but the unit runs less. I use this every night during summer and have noticed it cuts nighttime cooling costs roughly in half compared to maintaining a constant temperature.
Recommended AC settings for Korean summers
- Daytime (when home): 26-27°C, energy-saving mode, fan speed on auto
- Nighttime: Sleep mode starting at 26°C, with gradual temperature increase enabled
- Away from home: Turn off completely (modern units cool rooms quickly when you return)
- Fan direction: Horizontal or upward to avoid cold air blowing directly onto floor
Getting through tropical nights
Tropical nights are genuinely miserable if you don't adjust your approach. The outside air isn't any cooler than inside, so the usual strategy of opening windows won't help. What does help is focusing on personal cooling rather than trying to cool the entire room. Your body temperature drops naturally during sleep, and if you can help that process along, you'll sleep better even in warm conditions.
Cooling mats (쿨매트) are common in Korean households for good reason—they work through passive cooling, absorbing body heat without electricity. The gel or water-based versions stay noticeably cooler than your mattress. I use one from June through September, and the difference in sleep quality is significant. They cost ₩30,000-100,000 depending on size and material, which pays for itself quickly in reduced AC use.
Take a lukewarm shower before bed, but don't dry off completely. Leave your skin slightly damp and stand in front of a fan for a minute. The evaporative cooling effect will drop your core temperature quickly. This isn't comfortable in the moment—it feels cold enough to be almost unpleasant—but your body temperature stays lower for the next hour or two, giving you a window to fall asleep before warming back up.
If you're running AC at night, direct the airflow toward the ceiling or wall, not toward your bed. Direct airflow on your body while sleeping can cause stiffness or make you wake up feeling uncomfortably cold, even though the room temperature is reasonable. Korean AC units often have a "wind-free" or "indirect wind" setting that's designed specifically for sleeping comfort.
Sleep cooling checklist
- Use breathable cotton sheets, not synthetic materials that trap heat
- Consider a bamboo or buckwheat pillow (stays cooler than memory foam)
- Keep a damp towel on your forehead or neck if AC isn't available
- Drink water before bed (dehydration makes heat feel worse)
- Close curtains during the day to prevent bedroom heat buildup
Understanding progressive electricity pricing
Korea's electricity pricing system is structured to discourage heavy consumption, and it catches many people off guard when their summer bills arrive. The system isn't linear—you don't just pay more for using more electricity; your rate per kilowatt-hour increases as you cross usage thresholds. This means that the last 100 kWh you use in a month might cost three times as much per unit as the first 100 kWh.
As of 2024, residential rates work roughly like this: the first 200 kWh per month cost around ₩120 per kWh, usage between 201-400 kWh jumps to about ₩210 per kWh, and anything above 400 kWh costs approximately ₩310 per kWh. These rates get adjusted periodically, but the progressive structure remains. What this means practically is that if you use 450 kWh in a month instead of 390 kWh, that extra 60 kWh costs significantly more per unit than your average.
This is why it matters how you use your AC. Running it slightly less efficiently but staying under a pricing threshold can be cheaper than running it perfectly efficiently but crossing into the next pricing tier. I track my usage through the KEPCO app, which shows daily consumption. Once I see I'm approaching 400 kWh for the month, I become more aggressive about using fans instead of AC during cooler parts of the day.
Real example: My August 2023 bill was ₩185,000 for 480 kWh. My August 2024 bill was ₩142,000 for 380 kWh. I used only 21% less electricity, but my bill dropped 23% because I stayed under the 400 kWh threshold.
Check if you qualify for any discount programs. Low-income households, seniors, people with disabilities, and large families may be eligible for reduced rates or credits. These programs exist but aren't always advertised clearly—you typically need to apply through the KEPCO website or local office. Even a 10% discount becomes significant when dealing with summer electricity bills.
Quick wins that make immediate difference
Some changes provide disproportionate benefits for minimal effort or cost. These are the things I tell friends to do first, before they invest in new equipment or spend hours optimizing settings.
Close doors to rooms you're not using. This sounds obvious, but many people leave their entire apartment open, forcing the AC to cool spaces nobody's occupying. If you're working or relaxing in one room, close it off and cool just that space. You can always open doors in the evening when temperatures drop.
Hang a thick curtain or blanket over your front door if it faces outside. Korean apartment front doors, especially in older buildings, conduct heat surprisingly well. A thermal barrier here prevents that heat from radiating into your entrance area, which is often open to the rest of your apartment.
Turn off or unplug heat-generating appliances you're not actively using. Desktop computers, game consoles, older TV set-top boxes, and rice cookers on "keep warm" mode all put out steady heat. A desktop computer can add 200-300 watts of heat load to a room, which your AC then has to remove. I started shutting down my computer when not in use instead of leaving it in sleep mode, and my home office stays noticeably cooler.
Five-minute improvements
- Switch to LED bulbs if you haven't already (they produce much less heat than incandescent or halogen)
- Put aluminum foil (shiny side out) behind windows that get direct afternoon sun
- Move heat-producing appliances (computer, microwave) away from your AC thermostat
- Use the bathroom exhaust fan after hot showers to remove humid air quickly
- Store a spray bottle of water in the fridge for emergency cooling (mist skin, stand in front of fan)
Cook during cooler hours or use appliances that don't heat up your kitchen as much. I've started using my rice cooker and small electric pressure cooker on the balcony during heat waves instead of using the stove indoors. This keeps cooking heat outside of the living space. For people with covered balconies, this works well—just make sure appliances aren't in direct sunlight or getting rained on.
FAQ
Is it more efficient to run AC continuously or turn it on and off throughout the day?
For Korean summers, continuous operation at a moderate temperature (26-27°C) is usually more efficient than on/off cycling. Modern inverter ACs consume much less power when maintaining temperature than when initially cooling down a hot space. However, if you're leaving for more than 3-4 hours, turn it off completely.
Will a standing fan alone be enough without AC?
During typical Korean summer days (30°C+ with high humidity), fans alone won't be enough for most people, especially during tropical nights. Fans move air but don't lower temperature or humidity. They can extend the time before you need AC and reduce how much you run it, but expecting fans to replace AC entirely during peak summer isn't realistic for comfort.
Do window films make rooms too dark?
It depends on the film's VLT (visible light transmission) rating. Films with VLT above 50% reduce heat while keeping rooms reasonably bright. If you choose a film with VLT below 30%, yes, rooms will be noticeably darker. Read product specifications carefully—most Korean retailers list both heat rejection percentage and VLT.
How often should I clean my AC filter during summer?
Every two weeks minimum during June-August when you're using it daily. If you live in a dusty area or have pets, clean it weekly. The filter is washable—just rinse with water, let it dry completely, and reinstall. This single maintenance task can improve efficiency by 10-15%.
What temperature should I set my AC to when I leave for work?
Turn it off completely. Modern ACs cool spaces quickly when you return (typically 20-30 minutes to drop from 32°C to 26°C). Running it all day while you're gone wastes electricity and pushes you into higher pricing tiers. Some people set it to 28-29°C if they have pets, but for an empty apartment, off is most economical.
Can I install window film on double-pane windows?
Yes, but apply it to the inner surface of the inner pane only. Applying film to double-pane windows can sometimes cause thermal stress issues (the glass heats unevenly and can crack), though this is rare with modern windows. Check your window manufacturer's guidelines if available, or use films specifically marked as safe for double-pane glass.
Disclaimer
This article is for general informational purposes only and does not constitute professional advice. Electricity pricing details, product specifications, and AC efficiency recommendations may change over time. Please verify current rates through KEPCO and consult product manuals for specific appliance guidance. Safety considerations and building regulations vary by location—check with your building management before making modifications to windows or electrical usage patterns.
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