Inverter AC vs normal AC in Pakistan: the bijli bill comparison, explained

A normal (fixed-speed) AC has a compressor that is either fully on or fully off. It cools the room to the set temperature, switches off, the room warms, it switches on again at full power. Each restart is a surge of current. A DC inverter AC changes the speed of the compressor: it runs hard until the room is cool and then idles at a low speed to hold the temperature. No restarts, no surges, and much less current for most of the night.

• Long running hours: the longer the AC runs at low speed, the more an inverter saves. A bedroom AC running eight hours a night is the ideal case
• Insulated rooms: a room that holds its cool lets the inverter idle; a room with a west-facing glass wall keeps it at full speed, where it is barely better than a normal AC
• Correct tonnage: an undersized inverter runs at maximum all the time and saves nothing
• Voltage: inverters tolerate low voltage better and do not need a heavy stabiliser
• Manufacturers and NEECA labels commonly claim 30 to 50 percent lower running cost at part load; the real figure in your house depends on the four points above

A drawing room used two hours a day for guests, a shop that opens the AC only in the afternoon, or a rented house you will leave in a year: the inverter's higher price and more expensive PCB repair may never pay back. A well-serviced normal AC in a small, shaded room is not a bad machine.

Inverter ACs start gently, so a 5 kW solar system or a decent-sized generator handles one 1.5-ton inverter comfortably, while a normal AC's starting surge can trip the same system. Almost no home UPS runs any AC; do not buy an inverter AC expecting the UPS to carry it during load-shedding. If you plan solar, tell the installer which ACs you have; it changes the sizing.

Inverter ACs have a PCB in the outdoor unit that dislikes careless pressure-washing and voltage spikes. Repairs are board-level and cost more than a normal AC's simple capacitor or relay. The fix is not to avoid inverters; it is to use a technician who works on them daily and to service in the off-season. Post the job on Mechanics4U with the brand and the error code and ask specifically for inverter experience.