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Endesa - Electricity, Gas, People

The five questions to ask when buying an air conditioner

Published on June 27, 2019

Our well-being during the hot months depends to a large degree on our air conditioning: system. Most people are unable to answer the essential questions you must ask before making a purchase.

Summer challenges your heat tolerance, but fine-tuning your air conditioner is a simple task. The hard part is deciding what to do if you don't have an A.C. unit or if you want to replace the one you do have.

What should you look for when making a selection? How do you decide between one model and another? The following five questions are crucial for making this decision. If you know the answers, you’ll pass with flying colours.

1. What system should you choose?

Here, the answer is simple, because you only have three options to choose from:

  • Split-system air conditioning system: the most widespread and common form of A.C., with one unit or interior split (the one you turn on the expels cold air) and a second unit or exterior split (the one outside the house). The advantages that have led this system to dominate the landscape include its power and efficiency in providing both cold and heat. The downside is the installation process. Though it is not complex, it is more complicated than the other options.
  • Compact or window air conditioner: this approach incorporates both units in a single structure, usually in a cubic shape (it looks like a giant microwave). Decades ago, this was the most common kind of air conditioner (especially in office buildings). They are extremely easy to install, but they are less efficient than split-system air conditioners.
  • Portable air conditioning: small towers on wheels that you can move around the house according to your needs. They are not very efficient and only make sense as a quick solution for cooling down small rooms (preferably 20 square metres or smaller).

You will have to make a choice based on your goals for the air conditioner, which could range from basic (portable) to more advanced (two units), with the compact version as a happy medium.

2. What power do you need?

We should start by clarifying that the energy efficiency of your home plays an important role in this question.

Generally speaking, it is best to estimate a power of 100 BTUs per square metre. We have to convert BTUs to kW, which is the measurement used for electricity. We can do this by multiplying the BTUs by 0.86 and dividing the result by one thousand.

Thus, for 30 square metres, we get 3000 BTUs or 2.58 kW. This would be the power necessary for an A.C. unit intended to cool a large room.

The unit's power is going to end up fattening our bill: the higher the power, the more we end up paying. Therefore, it is important to consider that buying a unit with more power than we need doesn’t mean better climate control in the room, it just means higher costs (both for the unit and, later, for the regular energy bill).

An option that would result in less waste would be to make due with a pleasant temperature, reduce our estimate to 50 BTUs per square metre, and select an inverter system ,which is capable of maintaining a stable temperature while it operates at 40% of maximum performance. This way, we manage to lower our energy bill while also being quite efficient.

Expect to need an air conditioning unit with a power of around 2.58 kW to cool a large room.

3. What energy label should you select?

It’s easy to get lost amidst all of the energy efficiency labels out there, but they’re simpler than they appear.

Air conditioning units’ energy efficiency classification is based on a letter scale that spans from A, the most efficient, to G, the least energy efficient.

In turn, each unit’s label provides us with information about its performance in different climate zones, its seasonal energy efficiency when it’s cold (SEER) or when it’s hot (SCOP).

This information enables us to determine which model best fits our needs and particular conditions. If we opt for an A.C. system with an A in energy efficiency, we can expect a reduction in energy consumption of about 30%.

4. What else should you look for when choosing an air conditioner?

There are several factors unrelated to the unit itself that will have a key influence on its operation. These involve the characteristics of your home:

  • The energy rating of the home: amongst many other thing, the insulation of the walls and floors will affect how much cold air we lose and how fast we lose it, which, in turn, will affect the effort that the air conditioning unit must make (logically, more effort means a higher energy bill).
  • Our climate: an August in Seville isn’t the same as an August in Santander.
  • The home’s orientation and degree of exposure to direct sunlight.
  • The size of the windows and outer doors in square metres.
  • The length of the outside walls.
  • The number of people who are regularly going to be in a given room.

In general terms, the worse a home’s energy rating, the more severe the climate, the more exposed the home and the more people are living in it... the greater the power we will need from our air conditioner.

5. To what temperature should you set the air conditioner?

According to data from the Institute for Diversification and Energy Savings, the optimal temperature for our homes in the summer is between 23 and 25 degrees Celsius. Under no circumstances should the air conditioning be set to lower than these temperatures.

This is not just because of the impact on your health or questions of energy efficiency. You should also consider that setting the A.C. too high can have harmful effects on your health.

However, the feeling of of thermal well-being can vary significantly from person to person. This is due to several factors, including everyone’s particular metabolism and even the amount of “insulation” that each individual’s clothing provides.

Thus, the concept of comfort in shared spaces, such as homes and offices, can be disparate. It is worth noting that differences in metabolism between men, women and children can affect these margins by more than 25%.

Do not set the air conditioning too high: the Institute for Diversification and Energy Savings recommends setting your thermostat to between 23 and 25 degrees Celsius.