Office Air Conditioning Units: Which One Is Best For You?

With the summer heat having already teased us a few times this year we’re certain that your office will have already reached slightly uncomfortable temperatures.

You can loosen your tie and stock up the water cooler all you want but there’s no denying it, you will need office air conditioners this year. So rather than waiting for your staff to knock down your door in a sweaty rage why not look into renting an office air conditioning system now?

The fact of the matter is, whenever you decide to pursue portable office air conditioner rental, odds are you will find yourself in a world of confusing terms and calculations. Luckily for you we’ve decided to put together a handy guide for understanding how exactly office air conditioning works and what type is best for you.

How Many Office Air Conditioners Do You Need?

Before even thinking about what type of office air conditioning system would best suit your needs you need to work out how many you need. Although this can never be an exact science (unless you get a site survey carried out by one of our technicians that is) there are certain calculations you can make that will give you a rough idea.

An extremely rough guide to working out power required to cool certain spaces is:

7,500 BTU (2.2kW)

150 square feet

9,000 BTU (2.6kW)

250 square feet

10,000 BTU (2.9kW)

300 square feet

12,000 BTU (3.5kW)

400 square feet

13,000 BTU (3.8kW)

450 square feet

14,000 BTU (4.1kW)

500 square feet

This is by no means a foolproof system though. When it comes to working out portable office air conditioner requirements there are other things that need to be taken into consideration. For example, how many people inhabit your office space on a standard day? You also need to think about how many heat emitting devices, such as computers and monitors, exist in the area to be cooled.

Another important factor is the amount of direct sunlight your office is exposed to both as a result of the amount of windows and direction of the sun. All these different elements can have a massive effect on how hot your office can get and therefore how many office air conditioning units you will need.

Here are a few examples of this:

  1. If your room is heavily shaded you should reduce your cooling capacity by 10%.
  2. In contrast, if your room is very sunny, you should increase your capacity by 10%.
  3. For every extra person (above two people) that will be in the office you should add an extra 600 BTU to your capacity.
  4. If your office has a room that is hotter than normal, for example a server room, add 4,000 more BTU.

You see, it’s not quite as simple as you may have first thought.

It just so happens we’ve built a handy calculator to help you get a pretty accurate idea for how much cooling power you will need. It takes into account most of the above variables. Give it a go here.

What Types Of Portable Office Air Conditioners Are Available To You?

Now you have a rough idea of how much cooling capacity you require it’s time to decide what type of office air conditioning system would best suit your needs. There are a few types that have different pros and cons and that are better suited to different scenarios.



These units are the most practical and cost effective office air conditioners on the market, this is why they’re also the most common. Exhaust tube air conditioners work by pulling hot air in through grills on the exterior of the unit. The hot air is then moved through a refrigeration cycle where heat transfer is used to cool the air. The cooled air is then pumped out of the front of the machine whilst the heat is vented out of an exhaust tube at the rear. These machines simplicity can also sometimes be their downfall. Due to the fact they vent via such a short exhaust tube they must be located within a few metres of an external ventilation point such as an open window or ceiling void. This limits areas they can be used. The tubes can also suffer from heat bleed as vented heat can sometimes radiate back into the area that’s being cooled.



Split type units are by far the most efficient office air conditioning units available today. That’s why they’re also the most expensive. They work by using a glycol heat transfer medium that can be pumped between the main unit and the external ventilation box. Hot air is sucked into the main unit and heat transfer is used to cool it. The heated glycol is then pumped to the external box where the heat is expelled. The refrigerant then moves back around the circuit for the process to be repeated. While this occurs cold air is pumped out of the front of the machine. Although split type units also need some form of external ventilation they are far more flexible than exhaust tubes as they can reach up to 30 metres. There is also no danger of transferred heat being emitted into the cooled environment.



Evaporative coolers are slightly different to split and exhaust types. They don’t involve a refrigeration cycle at all and instead rely on the process of evaporation. A fan in the unit pushes hot air across a saturated cooling media. As the hot air passes through this media the process of evaporation, and therefore heat transfer, cools the air which then moves out into the area that requires cooling. Due to the fact these units require no ventilation they can be ideal for offices without opening windows. However, there are drawbacks to using evaporative coolers. Due to the fact they don’t utilise refrigerant they can’t be classified as climate control devices, they can only lower the temperature by a few degrees. Also, due to the fact they use water in the cooling process they can often increase the room humidity to uncomfortable levels.

In summary then, if you have plenty of external ventilation close by you can’t go wrong with exhaust tube air conditioners. If external ventilation is a little further away but you still want efficient climate control split type units are your only choice. Finally, if external ventilation is simply not an option, you’ll need to look to evaporative coolers to do the job.

Still Confused?

We hope this guide has at least started to help you understand what type of air conditioning unit would be best for your needs. However, as we’ve already stated, the only way to be sure that you are getting the correct type and amount of air conditioning power is to let one of our expert technicians carry out a free, no obligation, site survey. Within minutes they will be able to inform you on exactly what you need to get the job done perfectly. Contact us for more information.

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About the Author

Lauren King

Lauren works in our Ecommerce Team, with over 6 years of experience at HSS. She brings product knowledge and is able to give her advice on the right tool for the job no matter how big or small.

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