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How to Buy an Air Conditioner

Your complete buying guide with everything you need to know to buy an air conditioner.

How to Buy an Air Conditioner

1) How big is your room and what is in there?

Not all air conditioners will work effectively in every room, so it is important to find the right one to match the size of your room. It is also important to think about what the room is used for and how many devices or appliances there are that create extra heat. Also bear in mind that rooms such as a conservatory would require more powerful air conditioning than a room of the same size with small windows.

You can calculate the perfect size and power you need from an air conditioner using our Coolculator!

Coolculator »

2) How powerful should the unit be?

The amount of power an air conditioner has is given in BTU, or British Thermal Unit rating. This rating gives you an idea of how much cooling the machine is capable of.

A BTU is the amount of heat needed to raise the temperature of one pound of water by 1°F. When it comes to air conditioning, this measurement means the higher the BTU rating, the bigger the room it can cool. This also means that the higher the BTU, the more it will cost to run.

Coolculator »

3) What type of air conditioner do you need?

Air conditioners come in three forms: portable units, wall split units and ceiling cassette style units. They each suit different needs and situations but ultimately deliver the same results.

  • Portable UnitsPortable units are perfect for the home or any environment where versatility is key. They can easily be moved from room to room and between floors. Powerful enough to cool all room sizes without the stress of professional installation. Simply plug it in, vent and feel the benefits.Portable Air Conditioners »
  • Wall splitThese units require professional installation but do free up floor space. They are quieter than portable units and are mounted on walls with an external unit that removes the heat and any condensation from the room. As well as cooling, these units are also able to heat rooms more efficiently than central heating.Wall Split Air Conditioners »
  • Ceiling CassetteSimilar to wall split units, these require professional installation but instead of being mounted on your wall they are fitted into your ceiling. Similarly to wall split air conditioners, a ceiling cassette unit has an external unit to remove the heat and can also be used to heat rooms more efficiently than central heating.Ceiling Cassette Air Conditioners »

4) What features should you look for?

Air conditioners include a wide range of features so it is important to know which to look out for that would benefit you the most.

  • Mode SettingsMode SettingsMany air conditioners come with a variety of mode settings which include the ability to cool, dehumidify, fan and heat or even simply reduce the fan speed for a more comfortable night’s sleep.
  • Adjustable ThermostatAdjustable thermostatTake complete control over the temperature in your room. Find the most comfortable temperature and the thermostat will work to maintain a constant, optimum temperature in your home or office.
  • Aircon TimerTimerProgramme your air conditioner to automatically switch on and off helping to reduce energy costs. Set your unit to come on so you’ll come in to a cool home after work or set it to turn off once you’ve fallen asleep.
  • Sleep ModeSleep ModeThere's nothing worse than not being able to sleep at night because it is too hot! Buying an air conditioner with a sleep mode will mean noise levels are reduced and the temperature is adjusted to help you sleep soundly.

5) How much does Air Conditioning cost?

Everyone has a budget and different needs when it comes to buying an air conditioning unit. The cost of air conditioning varies between different requirements and efficiencies.

Ranging from as little as £200 for a portable unit and increasing in price depending on how powerful you need the unit to be, you’re sure to find one in your budget.

6) Are you able to vent an air conditioner?

All portable air conditioners need to be vented, ideally through a window or a wall but theventing hose can be placed through a slightly open door into another room or corridor. If you are unable to vent an air conditioner you will want to consider other options such as split units (wall or ceiling) or evaporative air coolers which are a great lower priced alternative to air conditioners.

Split air conditioning systems will need to be professionally installed and require an outdoor unit to expel the heat from the room, whereas an evaporative air cooler will not require any installation but must be used in rooms with good air flow and cannot be used in fully enclosed rooms due to the moisture they throw out into the air to assist with cooling.


» Do air conditioners need venting?

Yes. Air conditioners need venting in order to remove the warm, moist air from the system and your room. This is done through an exhaust hose on portable models which is placed out of an open window or door. Split units (wall split and ceiling cassette) do not require venting.

If you are unable to vent an air conditioner then an air cooler is a great alternative that would not require hosed venting but must be used in rooms with good air flow and cannot be used in fully enclosed rooms due to the moisture they throw out into the air to assist with cooling.

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» How does air conditioning work?

Simply put, air conditioners work in the same way as a fridge. They cool the air in your room by removing heat and moisture.!

First, warm air from the room is drawn into the system before being passed over a cold evaporator coil. Here the air is cooled and some of the moisture is removed.

A refrigerant then absorbs the heat from the warm air which is then vented through a wall or window via an exhaust hose. As this happens water condenses in the system which is either drained away or gathers in a tank for you to empty once full, however most air conditioners are self evaporating so will not need their tanks emptying regularly.

The cold air is then re-circulated into the room, reducing the overall temperature and humidity.

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» What types of air conditioners are there?

There are two main types of air conditioning units: portable units and split units.

Portable units are easy to move around your home or office and are often fitted with carry handles and castors. It is important to direct the hose from these units through an open window or door in order to vent the warm, moist air outside.

Split units come in two parts. They include an indoor unit that cools the room while the bulk of the hardware is mounted on the outside of the property, therefore massively reducing noise indoors. The two units are connected with copper pipe. This type of air conditioning unit is more efficient and also doesn’t take up as much space as a portable unit indoors.

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» What is BTU?

BTU stands for British Thermal Unit. It gives us an indication of the machine’s cooling capabilities and is a measure of the cooling power produced therefore determines the area it can cool. BTU ratings rise at a similar rate with room sizes, so that means a higher BTU rating will cool in a larger room than a lower rating.

BTU is measured as the amount of heat required to raise the temperature of one pound of water by 1°F.

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» What size air conditioner do I need?

The size of the air conditioner you need depends on the size of the area you want to cool. Units with a higher BTU will cool a larger space more quickly, but will use more energy than a unit with a lower BTU. It is important to consider the size of the room you need to cool when deciding what size air conditioner to buy.

You can calculate the size of air conditioner you need using our Coolculator.

Coolculator »

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» How cold can air conditioners make a room?

It is hard to put an exact figure on how cold an air conditioner can make a room as there are a number of factors that affect this. It will vary depending on the initial temperature of the room, temperature changes throughout the day as well as other factors such as the use of the room.

It can be said, however, that air conditioners do reduce room temperatures by several degrees. In general, our units have a minimum cooling setting of 16-18°C. Once your air conditioner reaches your desired temperature, the compressor will switch off and on automatically to maintain this temperature while the fan continues to move the air around the room.

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» How efficient are air conditioners?

Most of the air conditioners we offer have a minimum energy efficiency rating of A although the efficiency of each model depends on the amount of time the unit is turned on to and also the power level or mode setting it has been running in.

The most efficient way to run an air conditioner is to keep it running at a constant temperature, that way the room temperature never significantly increases requiring the air conditioner to work harder, therefore less efficiently, to cool the room again.

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» Can air conditioners heat a room as well?

Many air conditioners have a heating mode which acts alongside your central heating to increase the temperature in the room. Air conditioning units that offer a heating mode can be found by clicking here.

In general, air conditioners do use a lot of energy, but the user can have an effect on the amount their personal unit uses. Simply turning the unit off when the room is at a comfortable temperature, the amount of energy used will be drastically reduced.

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» How loud are air conditioners?

Portable air conditioners are louder than permanent, split models. This is because the majority of the moving mechanisms on the split models are on the outside of the building.

The noise level relates to the mode or setting the unit is performing under. Settings with a high fan speed tend to be louder but many models offer a night mode which helps to reduce noise for a quieter night’s sleep.

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» Do air conditioners need maintaining/servicing?

Regular, simple maintenance will keep your air conditioner running smoothly and reduces the risk of anything more serious going wrong with your unit.

Draining water away from portable units and cleaning the dust filters regularly ensures your air conditioner keeps working efficiently. It is recommended that split air conditioning units should be serviced annually to keep them running as efficiently as possible.

Browse our range of air conditioners.

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Room Size:

Length (m): Width (m): Height (m):

Heat Sources:


Devices (PCs, Monitors, Printers etc):

Total: BTUs of cooling required

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