Air conditioning is one of the largest single purchases a Pakistani household makes, and one where the wrong choice costs money every month for a decade afterwards. The upfront price difference between a good unit and a poor one is usually recovered within a couple of summers through the electricity bill alone.

This guide covers how to size a unit correctly, whether inverter technology is worth it, what separates the options, and what to check when buying used.

Sizing: the decision that matters most

Most people buy too large, believing bigger cools better. It does not. An oversized air conditioner cools the air quickly, hits the thermostat, shuts off, and restarts — repeatedly. That cycling uses more electricity than steady operation, wears the compressor faster, and leaves the room clammy because the unit never runs long enough to remove humidity properly.

An undersized unit runs continuously without ever reaching temperature, which is equally wasteful.

General guidance only. Actual requirement depends on ceiling height, insulation, glazing and sun exposure.

Inverter versus non-inverter

This is the second major decision, and in Pakistan the answer is usually clear.

Where an air conditioner runs for a few hours a week, the payback on an inverter unit is slow. In most of Pakistan, where an AC may run many hours a day through a long summer, the electricity saving typically recovers the price difference well within the unit’s life — often within two or three seasons.

One caveat worth knowing: inverter units have more sophisticated electronics, which means repairs can cost more and require a competent technician. Where you are far from good service, that is a genuine consideration.

Other specifications that matter

• Energy rating. Higher-rated units cost more upfront and less every month. Over a ten-year life the running cost dwarfs the purchase price difference.
• Cooling capacity in BTU, which should match the tonnage claimed.
• Heat and cool models provide winter heating — useful in northern Pakistan, largely irrelevant in Karachi.
• Low-voltage startup. Genuinely valuable where voltage fluctuates, which is much of the country.
• Refrigerant type. Newer refrigerants are more efficient and environmentally preferable.
• Warranty, particularly on the compressor, which is the expensive part. Compressor warranties are often longer than the general unit warranty — check both.

Buying a used air conditioner

Used ACs are widely traded in Pakistan and can be good value — but there are two failure modes that make a cheap unit expensive.

Installation matters more than people expect

A good air conditioner installed badly performs like a bad one.

• Outdoor unit placement — needs airflow and shade where possible. Boxed into an enclosed space, efficiency drops considerably.
• Pipe length — longer runs reduce efficiency. Keep indoor and outdoor units reasonably close.
• Proper vacuuming of the lines before charging. Skipping this shortens compressor life, and it is the step cheap installers most often omit.
• Correct gas charge — both under and overcharging cause problems.
• Drainage — must slope correctly or water backs up into the room.
• Stabiliser — strongly advisable given voltage fluctuation in much of Pakistan.

Reducing what it costs to run

• Set it to around 26°C rather than the lowest setting. Each degree lower increases consumption noticeably, and the room cools to the set point at the same rate regardless.
• Clean the filters monthly during the season. Clogged filters are the most common cause of poor cooling and high bills.
• Service annually before summer starts.
• Close doors and windows, and block gaps.
• Use curtains on sun-facing windows during the day.
• Run a ceiling fan alongside — circulating air lets you set a higher temperature for the same comfort.

Frequently asked questions

In short

Size it to the room rather than buying the biggest you can afford. Choose inverter unless usage will be light. Weigh the energy rating against the purchase price, because running cost dominates over a decade. Insist on seeing any used unit running before paying. And spend properly on installation, because it determines whether you get what you paid for.