Find what the mode actually changes
Manufacturers use labels such as eco, energy saver and sleep for different control behaviors. The LG LWHD6500 instructions provide one example in which the energy-saver fan stops when the compressor stops cooling. That older model’s behavior should not be treated as a definition for every current AC.
Write a short description from your own manual. Check whether temperature, fan operation, restart behavior or scheduling changes. A setting that quietly changes the target temperature cannot be compared as though only electrical efficiency changed.
Run a practical comparison
Choose similar outdoor conditions and the same occupied period. Record starting room temperature, setpoint, window coverings and doors left open. Measure complete-period kWh only with equipment appropriate for the AC and permitted by its instructions.
Also record whether the room felt comfortable and whether you changed settings midway. Exclude a trial that required switching modes repeatedly; it no longer represents either routine cleanly.
Convert the observed difference
Suppose comparable sessions hypothetically use 4.80 kWh in cool mode and 4.20 kWh in eco mode. The difference is 0.60 kWh, worth about 11 cents at $0.18/kWh. Across 20 similar cooling days, the estimated difference is $2.16.
That result applies to the modeled sessions. It does not prove the same difference during a hotter month, in another room or on another AC.
Keep the setting that serves the room
If a mode saves electricity but produces unacceptable temperature swings or noise changes, record that tradeoff. You may prefer it for one part of the day and another setting for a different routine. Check humidity concerns separately and report persistent performance problems. The purpose of the comparison is a repeatable comfort-and-cost decision, not forcing the lowest meter reading regardless of whether the room remains usable.
Choose your next step
Continue with the question that matches your next decision:
Sources & further reading
Numerical examples are illustrative unless explicitly described as measured. This guide does not claim hands-on product testing. Read the methodology and editorial disclosure.