Appliances

How To Compute Your Air Con's Horsepower Based On Your Room Size

If you want to cool your room properly, always choose the right air conditioner type and HP

Original Article: Cay Araneta Photography: Jilson Tiu (Main Photo)

Updated as of July 11, 2023

Living in a humid, tropical country means air conditioners are a staple throughout the year. And while most people base their purchase on the AC’s price or brand, a smart homeowner knows that there’s a lot more to that.

READ:
These Are The Energy-Saving Features To Look For When Buying An Air Con

Before investing in an air conditioner, you have to consider its horsepower (HP) and its energy efficiency. You must also factor in the type you want, and how appropriate it is to the room you are putting it in. To keep your cool while hunting for an AC, here are a three things you might want to keep in mind:

Split-type aircon in a studio room

1. Horsepower

Assess the air conditioner horsepower you need based on your room’s floor area. Or when in doubt, consult your air conditioner dealer. Here’s a quick guide:

Floor area (in square meters) / AC unit size (horsepower)

  • 10.5sqm: 0.5 hp
  • 11 to 14sqm: 0.75 hp
  • 15 to 21sqm: 1.0 hp
  • 22 to 25sqm: 1.5 hp
  • 26 to 28sqm: 2.0 hp
  • 39 t0 48sqm: 2.5 hp

 

Split-type aircon in bedroom

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2. The layout and the construction of your room

Once you’ve gotten a basic figure, take into consideration that your AC’s optimum unit size may increase or decrease based on the following factors of your room:

Window size

Larger, untinted windows will let in more heat.

Window location

Windows located in the eastern orientation let in heat from the rising sun (hot in the  mornings), while those in the west let in heat from the setting sun (warm mid-afternoons).

Insulation

Older houses with GI sheets for roofing offer little insultion, while newer homes have bubble foil or polyethylene ceiling or wall insulation that helps keep heat at bay.

window-type aircon in a room

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3. The air conditioner type

Window-type

With the window-type, fan and condensing unit are in one piece. This requires a hole or provision in the wall as big as the AC unit. These types of air conditioners are generally cheaper than their split-type counterparts. Maintenance and installation are simpler because all parts are contained in one unit.

Here's a 0.5hp window-type unit from Condura, available on Lazada for P11,850.

Split-type

Commonly used for bigger rooms and interior rooms, or areas without exterior walls for window-type units. A small hole is needed to connect the fan to the condensing unit, which can be located outside, between 50 to 100 feet away.

Here's a 1.0hp split-type unit from Sharp, available on Lazada for P24,535.

4. Insulation

The level of insulation in the room plays a crucial role in heat transfer. Well-insulated rooms retain cool air better, reducing the load on the air conditioner. Poor insulation may require a higher-capacity air conditioner to overcome heat loss.

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The size, number, and quality of windows and doors can impact the cooling load as well. Large windows or poorly insulated doors can allow heat transfer. As a result, your air conditioner will require a higher horsepower to effectively cool down the room.

For improved insulation, use black-out curtains (here's an option available on Lazada). You may also use door-sealing strips (such as this one available online) for a more controlled airflow inside the room. 

5. Ceiling height

Taller ceilings result in larger room volumes, and as such will require more coolingcapacity. If your room has high ceilings (above the standard height of eight to nine feet), you may need an air conditioner with higher horsepower.

Here's a 2.0hp split-type unit from Carrier, available on Lazada for P52,200.

6. Heat-Producing appliances

Consider the presence of heat-generating appliances like computers, refrigerators, or ovens because these appliances contribute to the heat load. Aside from that, their cumulative effect should be factored in when selecting the appropriate air conditioner capacity. More heat-producing appliances in a room means more time and cooling capacity needed for the room.

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In relation to this, the intended use of the room can influence the cooling load. For example, a kitchen may require a higher capacity air conditioner due to increased heat production compared to other rooms in the household.

Frequently Asked Questions

What happens if I choose an air conditioner with too low horsepower for my room size?

If the air conditioner's horsepower is too low for the room size, it may struggle to cool the space adequately. The air conditioner will have to work harder, leading to inefficient cooling, increased energy consumption, and easier wear and tear on the unit.

What happens if I choose an air conditioner with too high horsepower for my room size?

Opting for an air conditioner with excessive horsepower for a small room can lead to overcooling and uneven temperature distribution. This can result in discomfort, wasted energy, and higher electricity bills.

Can I rely solely on room size to determine the air conditioner's horsepower?

While room size is an important factor, it should not be the sole consideration. Other factors like insulation, room orientation, number of occupants, heat-generating appliances, and climate should also be taken into account for an accurate determination of the appropriate air conditioner capacity.

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Is it better to choose a slightly higher-horsepower air conditioner to ensure effective cooling?

It's generally not recommended to choose an air conditioner with significantly higher horsepower than required. Oversized units may cycle on and off more frequently, leading to poor humidity control, inconsistent temperatures, and increased energy consumption. It's best to choose an air conditioner that matches the cooling needs of the room.

Can a lower-horsepower air conditioner cool a larger room if used for a longer duration?

While a lower horsepower air conditioner may cool a larger room over an extended period, it may struggle to maintain a comfortable temperature during peak cooling demands, such as during noontime. This can result in inadequate cooling, discomfort, and increased energy consumption.

Should I consult with a professional HVAC technician to determine the appropriate air conditioner horsepower?

Consulting with an HVAC technician is highly recommended, especially for complex cooling requirements or if you're unsure about the factors impacting your specific situation. A professional can conduct a detailed assessment of your room, considering all relevant factors, and provide expert guidance on selecting the right air conditioner horsepower for your needs.

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This article originally appeared in the June 2005 issue of Real Living magazine. With reports from Nica Jose.

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