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Air conditioners: Air conditioner efficiency

A young girl stood by an air conditioning unit

They may cool the air, but air conditioners use lots of energy.

The cost of cool

Air conditioners literally guzzle electricity. The energy an average air conditioner uses in a day is enough to power a fridge for a week (between 19p and 36p). We base our running costs on 3 hours of use. A large electricity bill may affect you in the short term, but high energy consumption is likely to affect the environment in the long term.

Urban heat islands

On top of massive energy consumption, the use of many air conditioners can affect the local temperature. As the cool air is created inside, warm air is pumped outside. This creates urban heat islands. When you add up a city’s worth of air conditioners, you can understand why it is hotter in the city than the countryside in summer.

Refrigerants that warm the planet

Apart from all the energy they use, another environmental banana skin is the use of refrigerants. R410A or R407C are HFCs (Hydro Fluro Carbons), the most commonly used refrigerant type found in domestic air conditioners. HFCs don’t damage the ozone layer like CFCs do, but they are a much more potent greenhouse gas than carbon dioxide.

For a more environmentally-friendly refrigerant, look out for air conditioners which use R290 - an HC (hydrocarbon) propane-based refrigerant. This type is the best option as it’s ozone friendly and causes virtually no global warming.

Limit your electricity bill

Keep filters clean Filters blocked (with dust) make the machine work harder and use more electricity. So lightly vacuum every couple of weeks.

Use a timer A timer can automatically switch air conditioners on and off. This means that you can fall asleep with one on, but it can cut out an hour or so later. If your model doesn’t have a timer function, use a separate plug timer between the air conditioner and the plug socket.

Keeping cool the traditional way

In the short term:

  • Turn off all non-essential electrical equipment, including any computers and mobile phone chargers that aren't being used (as these generate heat).
  • Try to stay downstairs. Hot air rises, so the temperature upstairs is usually less comfortable than on the ground floor.
  • Keep windows, doors and curtains closed during the day. Once the temperature has cooled down in the evening, open them to allow airflow.

In the long term:

Row of mushroom-shaped trees

Trees can help create shade. Don't plant them too close to your home or you risk subsidence.

  • Effective insulation of roofing areas and walls will prevent cold air leaking out, as well as hot air in.
  • Windows can be bought with coating or treated in situ to reflect the sun’s hot rays.
  • Trees planted around the edge of the property will create shade – don’t plant them too close as they can cause subsidence.

Greener alternatives 

Air coolers 
They may be greener, but they're not as effective as air conditioners.

Air coolers work in a different way to air conditioners. Instead of using a pipes and refrigerant system, you fill them with cold water. When switched on, warm air passes over a wet filter, causing the water to evaporate which provides fresh cool air and a sea breeze effect.

While it’s far more energy efficient than an air conditioner, this method adds moisture to the air so isn't great for moist sticky days. Plus it can be a nuisance keeping the water reservoir topped up.

Portable electric fan

Fans use less power than air conditioners, but don't cool the air.

Electric fans

Fans use a fraction of the power of air conditioners as they only have to rotate three blades, but they only move the air around - they don’t cool it.

More on air conditioners...