Air conditioner choices and tips for staying cool inside

First published June 2009, last updated July 2013

While it’s winter here in Australia, in the northern hemisphere it’s summer and things have been really heating up in some countries. At the time of updating this article, it’s 3am in Las Vegas and the temperature there is 37C (98F). At 3am!

A few days back Las Vegas experienced temperatures of 47C (129F) and in Death Valley, the mercury climbed to 54C (129F).

Even by Australian standards, that is incredibly hot.

Unfortunately, most houses haven’t been constructed, insulated or positioned correctly in order to minimize the amount of artificial air conditioning required to keep temperatures indoors bearable throughout the summer months. Add to this the urban heat island effect and things can become very uncomfortable and even life threatening.

This will become an increasing challenge in the years ahead as global warming really starts to kick in and developing nations start having increased access to luxuries, or in some cases necessities, such as air conditioning. Millions more people will start using air conditioners and for longer periods.

Aside from the spike in electricity and water consumption connected to air conditioner usage that costs consumers and the environment a great deal, utility company transformers are well known to overheat and explode when air conditioning usage hits its peak during a heatwave, often cause massive blackouts and fires. The use of air conditioners also adds to the urban heat island effect.

Basic tips for staying cools indoors

Where I live is pretty much a desert state – it’s not unusual for temperatures here to hit above 100 degrees Fahrenheit (38 degrees Celsius) for days on end during summer. When we moved into our previous house, we were very surprised to find that the roof wasn’t insulated – at all.

Dark roof tiles and summer heat aren’t a really good combination; so instead of running the air conditioner for many hours a day, we invested in earth friendly roof insulation made from recycled cellulose fiber. It was a great investment, not only keeping us cooler during summer, but warmer during winter and increasing the value of our house. Additionally, it helped to reduce noise from outside.

But even with that insulation in place, the house still became quite hot at times – unfortunately it was built facing east-west instead of north-south as it should in the southern hemisphere to take advantage of passive solar warming during the winter months and present a side of the house to the sun with fewer windows during the summer.

To further reduce the need for air conditioning, over the summer we leave some doors and windows of the house that have security screens on them open from the evening through to early in the morning to let out pent up heat. We then shut the house up and draw the curtains as the temperature rises. When temperatures indoors get to the stage that it’s uncomfortable, then the air conditioner goes on – usually not until well after midday on the hottest days of the year.

Here are some other tips for staying cooler indoors without air conditioning:

– The use of ceiling and pedestal fans. While a fan on its own doesn’t reduce temperature, the movement of air over your skin evaporates perspiration causing a cooling effect – making the temperature feel up to 8 degrees cooler. You don’t need to be sitting directly in front of the fan to feel some benefit – it’s just a matter of getting air inside the room moving. If you decide to install a ceiling fan, try to buy one that has a reverse feature – it can then be useful in winter too.

– Gaps around doors and windows should be sealed to prevent hot air entering the house. Again, this will be of benefit during winter too.

– All electrical appliances generate heat; especially refrigerators and some TV’s. Plasma screens in particular are known to create a great deal of heat, to the point that some refer to them as space heaters.

If you’re not watching the TV, switch it off. Encourage your family not to have the refrigerator door open for extended periods and don’t overload your fridge. Turn off any appliance at the wall you’re not using (this will also reduce standby power consumption)

– Switch from incandescent bulbs to LED or Compact Fluorescent Lamps (CFL’s) as 80% – 90% of the energy consumed by incandescent lighting is wasted through heat. CFL’s will also save you money in electricity.

– Try to confine physical activity such as housework to the early hours of the day or late in the evening.

– Try to prepare foods that require the least amount of cooking as possible and use a microwave where you can. Ensure your range hood exhaust fan is switched on while cooking.

– Wear clothing that breathes, such as cotton. Avoid wearing shoes as our feet are also designed to be efficient heat exchangers. In fact, the less clothing you can get away with, the better as our bodies have quite an effective inbuilt cooling system.

– Curtains and shades should be a light color and of heavy material to help reflect/block the heat. Blackout curtains can also help keep heat in during winter.

– Keep rooms you don’t use often closed off.

– Plant trees around your house to provide a shade buffer between the sun and your walls. Use deciduous trees on the northern or southern side (depending on the hemisphere you live in) so you can still take advantage of passive solar warming in winter.

– Discourage your family from coming in and out of the house excessively. Each time the door is opened, a substantial blast of hot air will follow.

– Drink plenty of fluids, but steer clear of alcohol and sugar laden drinks.

– A spray bottle full of water kept close at hand can be a great way to get a bit of relief, particularly if there’s some air movement.

– A damp cloth applied to the back of the neck can help take the edge off the heat

Don’t forget about your pets.

Dogs don’t perspire, but cool themselves by panting. If your dog is panting rapidly and salivating heavily, this could be a sign of heat stress.

Make sure your pets have plenty of water and in the case of dogs, a spray every once in a while with a spray bottle containing water or a shallow tub with a few inches of water in it that the dog can stand in can be a big help.

Niki the Wonder Dog enjoying some respite during a heatwave
when temperatures reached as high as 48.5C (119F)!

After seeing the difference the tub idea made to the comfort of Niki the Wonder Dog, I tried it out myself and yes, it does really work. Even though only my toes were covered with water, it had a fantastic overall cooling effect. A minute or so standing in the tub and I’m good to continue enduring the 40+ degree celsius (105F +) temperatures we regularly experience for a while in a better frame of mind .

It does get to a stage in some parts of the world where the above simply won’t be enough. If you are considering buying an air conditioner, there are three types commonly used in homes:

Evaporative air conditioning

These units are also known as air, swamp or desert coolers and range in size from portable units suitable for single rooms to massive installations that can cope with entire complexes.

Rooftop evaporative air conditioners use a fan that draws in air through a wet filter. As the hot air passes through the filter (usually made of paper or straw), the water evaporates which cools and humidifies the air. Depending on temperature and external humidity, evaporative air coolers can reduce indoor temperatures by as much as 30° F (17° C).

Evaporative air conditioning isn’t a new invention – as mentioned above, nature has installed evaporative cooler in our own bodies in the form of perspiration. Artificial evaporative air conditioning was invented thousands of years ago in Iran. In its simplest form, a wind shaft in the roof of a dwelling would channel air over a small pond of water, cooling the air before being blown into the house. The Iranians had far more complex and efficient installations as well that still rival any modern electrical cooling appliance in terms of effectiveness.

Evaporative coolers are best suited to environments such as ours – they are incredibly effective in dry air climates. An evaporative cooler used in a humid environment will be totally ineffective and likely make discomfort even worse.

One of the great aspects of evaporative air conditioning is maintenance and running cost – up to 80% less than other forms of artificial air cooling. An evaporative air cooler is usually around 50% cheaper to purchase also. A negative aspect of evaporative air conditioning is water usage – around 3.5 gallons per hour for a ducted system on the average home; but refrigerated air conditioning also involves the use of water indirectly through increased electricity consumption.

If you find that only a single room in your home really needs air conditioning, small mobile evaporative cooling units can be purchased for under a hundred dollars.

Important tip: Evaporative air conditioning works best when you leave a couple of doors or large windows open – the cooling effect is dependent upon air turning over within a house. By running evaporative air conditioning with the house entirely shut up, you will increase humidity to uncomfortable levels and this can also cause issues with mold and electrical equipment malfunctions.

It may sound odd having a door open when it’s 115 outside, but as long as the door or window left open is on the opposite side of external air movement and not in direct sunlight, heat from outside will not enter – the air pressure from inside will keep it out. If you have an outdoors barbecue area or pergola attached to the house, it’s a great way to keep that a tad cooler too!

Refrigerated air conditioning

This type works very much the same way as your refrigerator, using the evaporation of a refrigerant liquid in a closed system to provide cooling. A compressor compresses the gas, which heats it. The gas then passes through coils allowing the heat to dissipate and for the gas to condense into a pressurized liquid. The pressurised liquid then passes through an expansion valve where it it hits a low pressure area due to the vacuum action of the compressor at the other end of the line. It then becomes a gas again at a much lower temperature, cooling the pipe that contains it. This gas flows through an insulated line to to a console unit containing a series of coils with a fan behind it; which sucks air from the room over the coils (unless it is a split system, then air is drawn from outside), cooling the air and then pushing it back into your home.

Refrigerated air conditioning also removes humidity from the air through the condensation of moisture on the cold evaporator coils. This condensate is drawn away to either evaporate in a pan over the warm condenser coils or just run directly outside.

While refrigerated air conditioning doesn’t directly use water, it does use a great deal more electricity than evaporative air cooling. That’s where the water usage lies; in the electricity generation process. When this is taken into account, the amount of water used by refrigerated cooling unit is approximately two thirds that of an evaporative unit.

The use of inverters in refrigerated air conditioning has delivered some energy savings – I’ve read claims of between 30 and 50 percent. Air conditioners without inverters need to stop and start in order to maintain a room’s temperature, whereas models featuring inverters automatically adjust the compressor speed.


Not as common for cooling applications as refrigerated or evaporative air conditioning, dehumidifiers are sometimes used in tropical locations to remove moisture from the air – a major contributor to a feeling of discomfort in higher temperatures. In a dehumidifier system, moisture laden air is drawn over a coil, much like a refrigerated air conditioner’s evaporator coils. Moisture from the air condenses on the coils, then drips into a pan or is piped into a drain. The air then moves over another warmer coil and is then blown back into the room.

While the resulting air isn’t really cooled, with the excess moisture removed it makes higher temperatures more tolerable. Dehumidifiers are used in situations where humidity is too high for an evaporative cooler, but refrigerated cooling cannot be used. The amount of electricity consumed is about half that of a comparable refrigerated air conditioning unit.

Air conditioners and off grid living

If you’re living off the mains grid and have limited access to water and power, it can be difficult to find a suitable air conditioner. I looked for many months for a unit I could use while in the bush and running off a small mobile solar power system. I finally stumbled across the MightyKool, a very portable personal evaporative air conditioner made in the USA. I’ve had it for a few seasons now and it’s absolutely brilliant. It only uses about a quart of water an hour and draws just .8 amps at its lowest setting. While it’s not a cheap item, it’s been worth every penny as there have been a few occasions where this powerful little air conditioner has likely prevented me from suffering heat stroke.

Artificial air conditioning – luxury or necessity?

The human race survived relatively well before air conditioning was powered by electricity and complex manufactured systems. The arrival of modem artificial cooling is somewhat a blessing and a curse due to the large amounts of energy required to run these systems – we need to use it wisely and see it as a luxury and privilege when it’s not being used in critical situations.

If you do run an air conditioner, before switching the cool on, try just running the fan for while until things really start heating up – it can save substantial energy and water. Also remember that the aim is to stay cool so you can function, not to create a refrigerator type environment – experiment with thermostat settings and find the highest possible temperature before you start feeling too uncomfortable.

I’ve noticed some houses in my neighborhood run their air conditioning units 24/7 over much of summer; but don’t bother closing curtains or taking other low/no-cost steps to minimize heat entering into their homes. It’s annoying to hear the hum of all the motors of a night time – more noise pollution – and the practice consumes an incredible amount of electricity.

While there are certainly situations where air-conditioning is a matter of life and death, I think we all need to toughen up just a bit when it comes to our expectations of acceptable living comfort levels. The planet depends upon us doing so.