Cooling Your Home Efficiently in Summer

An air conditioner moves heat outside

An air conditioner does not so much create cold air as pump heat from inside your home to the outdoors. The more heat that gets in, the more it has to move, and the more electricity it uses. There are two broad ways to cut summer cooling costs. One is to maintain the unit well and run it sensibly. The other is to reduce the heat that enters the home and the heat produced inside it. Filter care, the outdoor unit and operating tips are covered in the air conditioner cleaning article under Life Tips, so this piece focuses on the second approach: making a home where the AC does not have to work as hard.

Stop sunlight before it reaches the glass

Sunlight through windows is one of the biggest sources of daytime heat in summer. Once it passes through the glass and hits floors and furniture, it turns into heat that does not escape easily. Curtains or blinds on the inside block direct glare, but the heat that has already passed through the glass gets trapped between the curtain and the window. That is why awnings, overhangs and exterior shades, which stop the sun outside the window, work better when they are an option. If exterior shading is not possible, close inside curtains before the sun reaches that side of the house, and turn light-colored or reflective sides toward the glass.

Heat made indoors adds up

Heat generated inside the home raises the cooling load just as outside heat does. Stovetop cooking, ovens, rice cookers, clothes dryers, irons, and computers or TVs left on for hours all give off heat. While you are cooling, small changes in when and where you use them make a difference.

• Move heat-heavy cooking to cooler mornings or evenings
• Run the range hood during and right after cooking to vent heat and steam
• Use the dryer and iron when or where you are not cooling
• Turn off unused lights and screens, and consider replacing hot-running bulbs
• Avoid opening the fridge often or for long; it releases heat into the room too

Why a fan helps

A fan cannot lower the room temperature. What it does is move air across your skin, helping sweat evaporate and carrying body heat away, so the same temperature feels cooler. Raising the AC setting a little and running a fan alongside it can keep you about as comfortable while easing the load on the air conditioner. You can also point a fan along the path of the AC airflow to spread cool air through the room. Because a fan cools people rather than spaces, leaving one running in an empty room only uses electricity. Make switching off the fan the first thing you do when you leave a room.

Control humidity and comfort follows

Korean summers often feel oppressive because of humidity as much as heat. When the air is humid, sweat evaporates poorly, so the same temperature feels stickier and hotter. Air conditioners remove moisture as they cool, which means on muggy days lowering the humidity alone can make a room much more comfortable without dropping the temperature much. If your unit has a dry mode, it is worth trying on days that feel damp rather than hot. Dry mode does not always use less power than cooling, though; it depends on the design, so check the manual. Drying laundry indoors or leaving the bathroom door open raises indoor humidity, so avoid both while cooling.

Ventilate at the right time

Leaving windows open while cooling lets hot, humid air in and forces the AC to start over. Skipping ventilation altogether, however, leaves indoor air stale. The approach is to air the house briefly with a cross breeze in the early morning or at night, when it is cooler outside, and keep windows shut while cooling during the day. On nights that stay hot, keep those airing sessions shorter. If you come home to a house that has baked all day, open the windows for a few minutes to let the trapped heat out, then close them and start cooling.

Cool a smaller space

The larger the space an AC has to cool, the longer it takes and the more power it draws. Closing the door of the room you are using and cooling only that room gets it comfortable faster with the same unit. Keep doors to unused rooms closed, and check whether cool air is leaking through gaps toward the entryway or balcony. If air moves through gaps around window frames or doors, simple weatherstripping can help. On the other hand, if your system is designed to cool the whole home as one zone, follow the manufacturer's guidance so closed doors do not block the airflow.

Health comes before savings

Saving on cooling is pointless if the heat makes someone ill. Older adults, babies and young children, people with chronic conditions, and pets are especially vulnerable, so do not let indoor temperatures climb too high. If heat-related symptoms such as dizziness, headache, nausea or severe fatigue appear, move to a cool place, rest and drink water right away. If symptoms do not improve or the person becomes confused, contact a medical facility or emergency services immediately. At the other extreme, a very large gap between indoor and outdoor temperatures can be hard on the body, so avoid cooling to very low settings for long periods. Check official guidance for recommended indoor temperatures and heat wave advice.