How to Choose the Right Aircon Size (HP Guide for Malaysian Homes)

How to Choose the Right Aircon Size (HP Guide for Malaysian Homes)

Buying a new air conditioner? The biggest mistake most homeowners make isn’t choosing the wrong brand, but picking the wrong size. A unit that is too small will run constantly, driving up your TNB bill without ever cooling the room.

Understanding AC Sizing in Malaysia

We often rely on Horsepower (HP) as the standard measurement here in Malaysia. However, HP is actually a vague estimate rather than a precise scientific measurement.

A 1.0 HP unit from one brand might be less powerful than a 1.0 HP from another.

You should look at BTU (British Thermal Units) for accuracy. This number tells you exactly how much heat the unit can remove from the room per hour.

Real-World BTU Comparison

Not all “1.0 HP” units are created equal. Here is a quick look at how specifications vary between popular models you might find in electrical shops today:

• Daikin FTV Series (Non-Inverter): Rated at approximately 9,500 BTU.
• Panasonic Standard Inverter (PU Series): Rated at approximately 9,040 BTU.

This difference of nearly 500 BTU can affect performance in a borderline room size. Always check the spec sheet on the side of the box before you buy.

Quick Sizing Rule

You can use a simple calculation for standard Malaysian conditions.

For most homes, 1 HP covers approximately 100 to 150 sq ft.

We use these specific breakdowns for better accuracy:

• Bedrooms (Low activity): 1 HP per 110-130 sq ft.
• Living Rooms (High activity): 1 HP per 100 sq ft.
• Kitchens (Heat sources): 1 HP per 80-90 sq ft.

Room Size Chart

Factors That Affect Your Choice

The chart above serves as a baseline. You must adjust your calculation based on the specific features of your property.

1. Sun Exposure (The West Wall)

Rooms facing west absorb heat from 2 PM until sunset. This trapped heat radiates into the room well into the night.

• West-facing windows: Increase capacity by 20%.
• East-facing windows: Standard capacity is usually fine.
• Tinted windows: If you have installed high-quality solar tint, you can reduce the “West-facing penalty” by about half.

2. Ceiling Height

Most calculators assume a standard ceiling height of 9 to 10 feet. For every foot above 10 feet, add 5-10% to your required capacity.

High ceilings create a larger volume of air to cool. If you live in a duplex condo in Mont Kiara or a renovated terrace house with a double-volume ceiling, a standard sizing chart will leave you sweating.

3. The “Open Concept” Renovation

Modern Malaysian homes often knock down the wall between the living room and kitchen. You cannot size the AC for just the “living area” anymore.

Cool air acts like water; it will flow into every available space. If your living room is 300 sq ft but opens into a 150 sq ft dining area and a 100 sq ft kitchen, your AC is actually trying to cool 550 sq ft.

4. Insulation & Glass

• Floor-to-ceiling glass: Glass conducts heat much faster than concrete. Add 15-20% capacity if your room has a glass wall.
• Top floor: Roofs radiate heat downward. Add 20% capacity if you are directly under the roof.

Common Room Calculations

Let’s look at three specific scenarios we often see in KL and Selangor.

Scenario A: The Kepong Terrace Master Bedroom

• Dimensions: 12’ x 15’ (180 sq ft).
• Conditions: Concrete walls, standard 10ft ceiling.
• Calculation: 180 sq ft falls into the 1.5 HP range.
• Verdict: A 1.5 HP inverter unit is perfect here.

Scenario B: The Condo Living Room (West Facing)

• Dimensions: 15’ x 20’ (300 sq ft).
• Conditions: Large glass balcony door facing the afternoon sun.
• Calculation: Base requirement is 2.5 HP.
• Adjustment: Add 20% for the sun exposure.
• Verdict: You should upgrade to a 3.0 HP unit. A 2.5 HP unit would struggle to maintain 24°C on a hot afternoon.

Scenario C: Combined Living + Dining

• Dimensions: 25’ x 20’ (500 sq ft).
• Conditions: Open layout.
• Verdict: A single unit might struggle to push air across the entire 25-foot length.
  • Option 1: Two separate units (2.0 HP + 1.5 HP) to create zones.
  • Option 2: A powerful 2.5 HP unit positioned centrally, aided by a ceiling fan to circulate the cool air.

Why Undersized AC is a Financial Risk

“I’ll just save RM300 and get the smaller unit.”

This is a common thought process that leads to higher monthly costs. An undersized unit never reaches its “cut-off” temperature. It runs at 100% capacity continuously.

The Tariff Impact TNB electricity tariffs are tiered.

• Standard Usage: Blocks 1 & 2 charge 21.8 to 33.4 sen per kWh.
• High Usage: Once you exceed 600 kWh, the rate jumps to 51.6 sen. If you hit 900 kWh, you pay 57.1 sen per kWh.

An undersized aircon running non-stop can easily push your household consumption into these expensive top tiers. You might save RM300 on the machine but pay an extra RM50-RM100 every single month in electricity.

Why Oversized AC is Also a Problem

“I’ll get a bigger one just to be safe.”

This approach creates a different set of issues. An oversized unit cools the room too fast and shuts off before it has removed the moisture from the air.

• The Result: The room feels cold but “clammy” or sticky.
• The Wear: The compressor cycles on and off frequently (short-cycling), which stresses the motor and shortens the lifespan of the unit.

Inverter vs Non-Inverter Sizing

Non-inverter (Fixed Speed): You must size these accurately. They have no ability to adjust their output. If you buy a 2.0 HP non-inverter for a 1.0 HP room, it will blast freezing air for 10 minutes and then shut off, causing massive temperature swings.

Inverter (Variable Speed): These units can vary their compressor speed to match the cooling load.

• Flexibility: An inverter can slow down to maintain temperature.
• Sizing Strategy: You can slightly oversize an inverter without major penalties, as it will simply run at a lower, efficient speed once the room is cool.

Refrigerant Update: Most modern inverters now use R32 refrigerant. This gas is more efficient and has 3x lower global warming potential than the older R410A.

Installation Matters: The “Insider” Detail

Even the perfect machine will fail if the installation is poor.

The Copper Pipe Thickness Rule R32 gas operates at a higher pressure than older models. Ensure your installer uses copper pipes with a thickness of at least 0.61mm.

Some contractors use thinner 0.51mm pipes to cut costs. These thin pipes are prone to leaking under the high pressure of modern R32 systems. Ask your installer to confirm the thickness before they start work.

Unit Placement Tips

• Indoor Unit: Mount it high on the wall, but leave at least 4-6 inches from the ceiling for airflow.
• Outdoor Unit: Avoid placing it in direct direct sunlight if possible. A shaded compressor works less hard and lasts longer.

Professional Assessment

While this guide helps you estimate, you should consider a professional site visit if:

• Your room has an L-shape or odd layout.
• You have a server room or gaming PC setup generating extra heat.
• You are cooling a commercial space with high foot traffic.

Ready to Install?

Need help choosing or installing the right AC for your home? WhatsApp us at 012-2252 623.

We provide:

1. Site Evaluation: We check your room size, orientation, and heat sources.
2. Unbiased Recommendations: We suggest the right HP and brand for your budget.
3. Professional Installation: We use quality 0.61mm+ copper piping and perform proper vacuuming.

Our team serves Kepong, Mont Kiara, Desa ParkCity, and surrounding Kuala Lumpur areas. Contact us today for a free sizing consultation!