New Aircon Buyer's Guide: BTU Sizing, Inverter vs Non-Inverter and Power Draw

For most Singapore bedrooms of 10 to 15 square metres, a 9,000 BTU indoor unit is the usual match, while a living or dining area of 20 to 30 square metres often needs 18,000 to 24,000 BTU. An inverter system costs more upfront but modulates its compressor to hold a steady temperature, so it typically draws less electricity over a year than a non-inverter unit that switches fully on and off. Sizing correctly and choosing the right type matter more for your bill than chasing the highest tick rating alone.

Aircon is the single largest electricity user in many local homes, so getting the buying decision right saves money for a decade. This guide covers how BTU sizing works for our climate, the real difference between inverter and non-inverter, how to read power draw and tick ratings, and what a proper installation involves. The numbers here are ranges, not fixed quotes, because room layout, sun exposure and ceiling height all shift the answer.

What is BTU and how do I size an aircon for my room?

BTU (British Thermal Unit) measures cooling capacity. A higher BTU figure means the unit can remove more heat per hour, which matters because Singapore rooms take on heat from strong sun, west-facing windows, and closely packed HDB and condo layouts. Undersizing leaves a room that never gets cold enough; oversizing cools too fast, cycles off before removing humidity, and leaves the space feeling clammy.

As a rough starting point for local conditions, plan for roughly 500 to 700 BTU per square metre, then adjust upward for west sun, large glass windows, high ceilings, or a room with many people or heat-generating electronics. Use these as a guide, not gospel:

• Small bedroom, 10 to 14 sqm: around 9,000 BTU
• Larger bedroom or study, 14 to 18 sqm: around 12,000 BTU
• Living or dining area, 18 to 28 sqm: around 18,000 to 24,000 BTU
• Open-plan living and dining, 28 sqm and up: 24,000 BTU or a multi-split setup
• West-facing or heavily glazed rooms: add roughly 10 to 20 percent

What is the difference between inverter and non-inverter aircon?

A non-inverter compressor runs at full speed until the room hits the set temperature, then shuts off completely, then restarts when the room warms again. This on-off cycling uses more energy at each start and lets the temperature swing. An inverter compressor instead speeds up and slows down continuously, holding the room close to the set point with less energy once it settles.

For the way most Singapore households run aircon, meaning long hours in bedrooms overnight, inverter units usually win on running cost and comfort, and they are quieter. Non-inverter units are cheaper to buy and can make sense for a room used only briefly. Here is the trade-off at a glance:

• Upfront cost: non-inverter is lower; inverter is higher
• Running cost over long hours: inverter is typically lower
• Temperature stability: inverter holds steadier, non-inverter swings more
• Noise: inverter generally runs quieter
• Best fit: inverter for daily and overnight use, non-inverter for occasional short use

How do I read power draw and the tick rating?

Every aircon sold here carries a Mandatory Energy Label with a tick rating from 1 to 5, where more ticks means better efficiency. The label also shows an estimated annual energy cost based on standard assumptions, which is useful for comparing two models side by side. Efficiency is expressed through metrics you may see quoted as COP or the seasonal figures on the label; a higher number means more cooling per unit of electricity.

To estimate your own running cost, look at the unit's power input in watts, convert to kilowatts, multiply by hours used per day, then by your electricity tariff. As a worked example, a system drawing about 0.9 kW run for 8 hours a night is roughly 7.2 kWh per day; at a tariff in the region of 30 cents per kWh that is a little over 2 dollars a night for that unit, before factoring in that an inverter rarely runs at full draw the whole time.

• More ticks on the energy label means lower running cost for the same cooling
• Compare the annual energy cost figure between models, not just the tick count
• Match capacity to the room first; an oversized 5-tick unit can still waste money
• Rough monthly cost = kW draw x hours per day x 30 x your tariff rate

Single-split or multi-split: which system suits my home?

A single-split system pairs one outdoor condenser with one indoor unit, which suits a single room or a small flat. A multi-split system connects one outdoor condenser to several indoor units, common in condos and larger HDB flats where balcony or ledge space for condensers is limited and you want to cool two, three or four rooms.

Multi-split saves outdoor space and can look tidier, but the condenser must be sized for the total load, and running many rooms at once demands more capacity. Check your ledge or aircon compartment space and any condo or town council rules on condenser placement before deciding, since this often drives the choice more than preference does.

What does a proper aircon installation involve?

A clean installation is what protects the efficiency you paid for. Poorly done copper piping, a badly vacuumed line, or a wrongly placed condenser will make even a 5-tick inverter underperform. Because the outdoor unit and the connection sit on a dedicated circuit, the electrical side matters too: the supply must be correctly rated, properly earthed, and the isolator and wiring sized for the load, which is where a licensed electrical and aircon installation team earns its keep.

Getting the installation done properly by an experienced local team means the piping run is kept short and sealed, the system is vacuumed and gas-charged correctly, condensate drains away with a proper fall, and the electrical connection is safe and compliant. If you are also renovating, coordinating the aircon trunking, ceiling work and wiring together gives a neater result than retrofitting later.

• Correct copper pipe sizing and a short, insulated run
• Proper vacuuming and refrigerant charge to the maker's spec
• Condensate drainage with enough fall to avoid leaks and ceiling stains
• A correctly rated, earthed electrical supply and isolator
• Condenser placed with airflow clearance and within building rules

How can I keep running costs and repairs down?

Set the temperature to a sensible 24 to 25 degrees rather than the coldest setting, since every degree lower adds to the bill without much comfort gain. Clean or wash the indoor filters every few weeks in our dusty, humid climate, because a clogged filter forces the unit to work harder and cool less.

Book a general servicing a few times a year and a chemical wash when cooling drops or smells appear. Regular maintenance keeps efficiency up, catches small refrigerant or drainage problems before they become big repairs, and extends the life of a system that should last well over a decade when looked after.

Frequently asked questions

Is a bigger BTU aircon always better? No. An oversized unit cools the room too quickly, then shuts off before it has removed enough humidity, leaving the space cold but clammy and wasting energy on frequent restarts. Matching BTU to the room size and sun exposure gives better comfort and lower bills than simply buying the largest unit.

Is inverter really worth the extra cost in Singapore? For rooms used many hours a day, such as bedrooms run overnight, the lower running cost and steadier comfort usually justify the higher purchase price over the life of the unit. For a room switched on only briefly now and then, a non-inverter unit can be the more economical choice.

How many ticks should I look for? More ticks means better efficiency and lower running cost, so a 4 or 5-tick model is a sound target if the budget allows. Still, size the unit to the room first, because an oversized high-tick system can cost more to run than a right-sized one.

Do I need a licensed contractor to install aircon? Yes, for both safety and performance. The refrigerant work, the drainage, and the electrical connection all need to be done correctly and to code, so use a qualified aircon and electrical installation team rather than an unverified handyman.