Guide written by:
Jeremy, construction site supervisor, Cardiff
Essential for keeping cool in the summer months, portable air conditioners allow you to freshen up the air and lower the overall temperature of your living space. Whether you choose a monoblock or split unit, your decision will come down to the volume of the room and the features on offer. Read on for our top tips!
- Monoblock air conditioners
- Split air conditioners
- Air coolers
- Volume and surface area
- BTU and power
- Coefficient of performance
- Filtering and noise level
- Reverse cycle
Portable air conditioners: the essentials
There are a few different types of portable air conditioners which differ in terms of performance:
- Single hose air conditioners: inexpensive, feature a single hose to pass through a window, arguably the most common type of portable air conditioner;
- Dual hose air conditioners: more expensive but offer better performance and are less energy-intensive, feature two hoses to pass through a window;
- Split air conditioners: the most expensive option but also the quietest as the compressor is housed in the outdoor unit while the rest of the unit is indoors, features two hoses to pass through a window;
- Air cooler: inexpensive and lightweight, cools air by a few degrees in rooms measuring less than 15 m², does not strictly 'condition' the air.
Main factors to consider when choosing a portable air conditioner:
- The surface area (m²) or volume (m³) of the room you want to cool.
- The energy efficiency rating of the unit (from A to G or A+++ to D), A and A+++ being the most energy efficient.
- The COP (coefficient of performance): the higher the COP, the more efficient the air conditioner.
- The sound level measured in dB: 55 dB on average, less for the quietest models.
- Additional options for air conditioners:
- A remote control to change settings without having to get up.
- A programmer for different time, cycle and air con settings.
- A fan mode.
- A dehumidifying mode.
- An air ioniser to ionise air for well-being.
- A reverse cycle to turn your air conditioner into a heating applicance.
Please note: all air conditioners require some form of maintenance.
How do air conditioners work?
Contrary to popular belief, airconditioning doesn't involve producing cold air, but rather extracting hot air from one space to another.
Without going into any overly technical details, portable airconditioning units basically work just like refrigerators. They function via heat exchange that occurs thanks to a refrigerant fluid contained within the unit and processes of compression, condensation and release of the recovered heat energy.
The air expelled back into the space by the unit's ventilation system has therefore been freed of some of its heat which helps to cool the air in the surrounding space. The remaining hot air will either be released outdoors or condensed, depending on the type of unit you have.
Air conditioners offer an almost instantaneous cooling effect when the unit is switched on. These days, the vast majority of mobile air conditioning units operate automatically. As such, a temperature sensor measures the ambient temperature in real time. The unit then electronically calculates the excess heat to be extracted and the amount of fresh air to be returned to reach your desired target temperature. This process depends on the power of the unit and its compression capacity.
What are the different types of portable air conditioners?
There are three main types of portable air conditioner: the monoblock systems, split system and the self-evaporating portable air conditioners.
Monoblock portable air conditioners
Single-hose monoblock air conditioners
Monoblock single-hose air conditioners are the quickest and simplest type of unit to use. As the name suggests, the whole air conditioning mechanism is incorporated in a single unit mounted on wheels. Ideal as an auxiliary air conditioning system and easy to move from one room to another, monoblock units do, however, require exterior drainage.
This drainage is performed by a flexible hose (100–150mm in diameter) that can be fed through a window or a hole in an external wall. Power ratings vary from 2000–3500W, meaning a surface area of over 35m2 can be serviced by a single unit. However, pay attention to the level of soundproofing on the casing as this type of air conditioning unit is often noisy (>60dB).
More sophisticated monoblock models also provide a ventilation-only or dehumidifying mode to circulate or remove moisture from the ambient air without cooling it. High-end airconditioning units are also programmable by means of a built-in clock (start, stop, desired target temperature, etc).
Dual-hose monoblock air conditioners
Monoblock dual-hose air conditioners feature two hoses: one for collecting outdoor air and the other for releasing hot air. This process allows you to freshen ambiant air without bringing in any hot air from outdoors and without the use of pressure which requires more energy.
Split portable air conditioners
Portable split air conditioners work exactly like monoblock models, but they consist of two separate parts. The condensingand compression unit is installed outside the property, while the portableventilationunit can be placed indoors (as long as it is connected to the external unit via a flexible hose).
As you may have guessed, split models are less portable than monoblock units, since the ventilation unit has to be positioned close to the external compression unit.
The major advantage of split models is that the mobile ventilation unit is lighter and less bulky and produces much less noise! Similarly to monoblock units, power ratings vary from 2000 to 3500W.
Most split air conditioners also offer ventilation-only and dehumidifying modes. Like movable monoblock models, high-end split models are also programmable. They are, however, more expensive than their monoblock counterparts.
Self-evaporating portable air conditioners
'Self-evaporating air conditioner' is actually a bit of a misnomer. Have you ever seen a car without an exhaust pipe or a fire without smoke? Well, the same goes for air conditioning!
So-called non-drainage models are in fact "coolers" that function by condensation. They aren't really air conditioning systems at all. However, they are affordable, small, lightweight and suitable for cooling small spaces (if only slightly!). However, they're generally quite noisy and are ineffective on floor areas over 15m2.
Most coolers must also be refilled with water quite regularly. They provide a useful occasional solution, but lack both the efficiency and the precision control of a real airconditioning device (monoblock or split). As such, they do not offer the cool and comfort you'd expect from a real air conditioning unit.
Portable air conditioner features
In addition to choosing between a monoblock or split model, consider the following features to ensure that the air conditioner you select meets your needs.
Refrigeration capacity is expressed in BTU (British Thermal Units). 1 BTU = 1055 Joules (J) and 1W equates to 3.414 BTU. This is the main factor in determining whether or not a given model will be sufficient for your space.
To help you calculate, an air conditioning unit must have a minimum output of 7000 BTU (~1950W) for a space up to 15m², 9000 BTU (2500W) up to 25m² and 12000 BTU (3500W) up to 35m².
To scale your air conditioner appropriately, account for about 100–130W per m² (assuming a ceiling height of around 2.5 m). Size up if the space to be cooled has bay windows, french doors, etc., or if it faces due south.
Cooling capacity and surface area comparison
BTU refrigeration capacity
Power of air conditioning unit
Surface area of space
Maximum volume of space
37 m 3
62 m 3
87 m 3
135 m 3
Mobile air conditioning units are relatively energy-intensive. Energy consumption is therefore a factor to consider when making your choice.
Like other appliances, air conditioning units are classified according to their energy consumption (from A to G or A+++ to D). The ideal is, of course, a class A or A+++ air conditioner.
Coefficient of performance
This expresses performance as a ratio between electrical power consumed and refrigeration power restored. To cut to the chase – rather than bore you with tedious calculations! – the higher the COP, the more efficient the air conditioning unit.
As mentioned above, portable air conditioners (especially monoblock models) are often quite noisy. There is no such thing as a totally silent model! While 50dB (decibels) represents a low level of noise, the most poorly soundproofed units can reach 70 or 75dB. Generally speaking, the level of soundproofing will have a significant impact on price; but it might be a fair price to pay to keep cool in relative 'silence'.
Air conditioning units
Additional features for portable air conditioners
There are a few air conditioner accessories designed for greater comfort and ease of use.
It's well worthwhile to be able to program your air conditioner if you want to be able to arrive home to an already perfectly cool living space, or if you want to power down automatically when everyone's in bed. Programming can help with the electricity bill too (through temperature management, delayed start, set cycles etc.).
Ventilation-only and dehumidifier modes
Some air conditioners also offer alternative modes, such as ventilation-only mode (the unit then acts simply as a fan) or dehumidificationmode.
This mode allows you to rebalance the ions in your home – a process linked to general well-being
Remote controls can be very handy, depending on the intended use and location of your air conditioning unit.
Activated carbon filter and electrostatic filter
Some air conditioning units are equipped with additional filters to purify the cooled air they expel. Activated carbon filters are effective at removing odours while electrostatic filters are great for fighting bacteria and dust. These features are especially useful if you or a member of your family suffers from respiratory problems such as asthma.
To avoid the nuisance of a loud air conditioner, choose a unit with the Eurovent label, or with a Sleep or equivalent setting. This will ensure you are exposed to only low decibel (dB) levels.
Reverse cycle air conditioners
Some air conditioners offer reverse cycles meaning they also function as heaters. Before you jump at this exciting prospect, however, always be sure to check the coefficient of performance of air conditioning units before you buy.
Caring for your portable air conditioner
As with any other appliance, maintenance is necessary to ensure your air conditioning unit keeps functioning as expected.
If you opt for a split system, you'll have to work your magic on both parts of the system: outside and inside. For monoblock systems, everything happens inside the one box. Maintenance is generally limited to cleaning the filters and draining thewater tank. Overall, you shouldn't have too much trouble, whichever model you go for.
However, you should also remember to descale your air conditioning unit once a year.
Final tips on choosing your portable air conditioner
These days, decent air conditioning is within everyone's reach! However, you do need to know how to use your air conditioning unit.
The first thing to remember is that you need to place your air conditioner near a window (or other evacuation route) regardless of type (monoblock or split): the shorter the evacuation circuit, the better the performance.
Avoid extending the flexible hose that comes with your unit at all costs. If it is too long, condensation will accumulate inside and mould will quickly set in.
When setting your air conditioning unit, the targettemperature should be no more than 8°C lower than the maximum outdoor temperature to avoid thermal shock (5°C is ideal).
To maintain good air quality, clean the filters regularly. Drain the water tank(s) at the same time.
In terms of energy consumption, for an average air conditioning unit, expect an increase of about 15% per month for a daily use of 3–4 hours. For this reason, it's best to choose a programmable model with a class A energy rating and a high COP.
In the autumn, before unplugging your air conditioner, run it for a few hours in ventilation-only mode (if possible) to dry all the pipes and ducts for storage. Follow the same routine in spring for several hours when the heat starts to pick up.
To find out more about optimising indoor comfort, follow our editors' advice and check out their other guides:
Guide written by:
Jeremy, construction site supervisor, Cardiff, 128 guides
Electrician by trade, I first worked in industrial estates where I installed, wired and fixed a large number of electrical installations. After this, I managed a team of electricians for this type of work. 10 years or so ago, I turned to building and construction. From the modest family home, to gyms and theatres; I have been able to coordinate, audit and organise all sorts of construction sites. for 4 years now, I am restaoring and bulding an extrension to a bungalow in the heart of the welsh countyside. My experience in manual work and my knowledge means I am proud to be of service. Terraces, interior design, roofing, plumbing, electricty, anything goes! We have, my wife, daughter and I, built almost everything we have from scratch! So to answer all of your questions, and to orientate and advise you on coosing your tools? Easy!