Test method

How we test air conditioners

The uses we score and the tests we run on every AC: cool-down at 45 °C, power over an eight-hour night, bedroom noise, inverter and low-voltage running.

Air Conditioners reviews

Every air conditioner we review goes through the same uses and tests below, in a real bedroom of an Indian flat, over four to six weeks of summer heat, on the unit we bought or borrowed. That is what makes the results comparable: a cool-down time or a night’s power use means the same thing for every AC on the site, though room sizes differ slightly and each review states the room it used.

Where a review turns units into a monthly bill, it states the tariff it used, so you can redo the sum with your own rate. Each test result in a review links back to the matching test on this page.

What we score

Peak summer heat
How quickly it cools a bedroom on a 45 °C afternoon, and whether it holds the set point afterwards instead of drifting up.
Overnight bedroom use
How quiet the indoor unit is at night and how steadily it holds the room temperature through an eight-hour night.
Running cost
How much electricity it draws once the room has settled and over a full night, which is what decides the monthly bill.
Power cuts and low voltage
Whether it starts and runs on a home inverter during a cut, and keeps cooling when the supply sags on summer evenings.

The tests

  1. Cool-down, 34 to 24 °C

    Measured in min Lower is better

    We start with the test bedroom at 34 °C, set the AC to 24 °C on turbo and time how long the room takes to reach 24 °C. Room size varies by review (130 to 160 sq ft), and each review states the room it used.

  2. Cool-down at 45 °C outdoors

    Measured in min Lower is better

    We repeat the 34 to 24 °C cool-down on afternoons when the outdoor temperature is 43 to 46 °C, the conditions north and central Indian homes see in May and June, and time it the same way.

  3. Holds 24 °C at 45 °C outdoors

    After the 45 °C cool-down we keep logging the room temperature for the next hour. Pass means the room stayed at the 24 °C set point; fail means it crept up while the compressor ran near full speed.

  4. Power draw, settled at 24 °C

    Measured in W Lower is better

    Once the room has settled at the 24 °C set point, we read the AC's power draw from a plug-in power meter on its supply. This is the draw you pay for through most of an evening.

  5. Energy over an eight-hour night

    Measured in units Lower is better

    We log the electricity the AC uses over an eight-hour night in the test bedroom with the same plug-in meter. One unit is one kWh, as on your electricity bill.

  6. Indoor noise, low fan

    Measured in dB Lower is better

    We measure the sound level 1 metre from the indoor unit with the fan on its lowest speed, the setting most people sleep with.

  7. Indoor noise, turbo

    Measured in dB Lower is better

    We measure the sound level 1 metre from the indoor unit in turbo mode, as it runs during a fast cool-down.

  8. Runs on a 3 kVA home inverter

    We switch the AC onto a 3 kVA home inverter as it would run during a power cut. Pass means it started and kept running without tripping the inverter.

  9. Keeps cooling at 185 V or below

    We run the AC with the supply dipped to 185 V, or to 180 V on some units (each review says which), the low end of what many Indian homes see on summer evenings. Pass means it kept cooling without tripping.