I'm planning to buy an air cooler as it is less expensive to purchase and operate than an air conditioner.
Are there any air coolers that can achieve same, or close to, the cooling effect that an air conditioner can achieve?
Depending on your environment an air cooler may or may not be effective.
Here's a chart to help you determine if your situation would be a good fit.
The table above presents relative humidity in columns (vertical) and air temperature in (rows) horizontal.
The cells inside the table have the temperature that can be obtained with the use of air coolers (effectiveness).
The ideal temperature for comfort is highlighted in green. It ranges from 70 to 75% depending on the temperature and relative humidity.
If the interception of the values that represent the air temperature in your areas and relative humidity in your area is above the value that is considered ideal, that means that air cooler will not be effective in your area.
If you think about the range of temperatures and humidity levels you experience the question is - can I cool to the level I need?
If the answer is "yes" you are good to go.
If the answer is "no" you need a different solution.
If the answer is "sometimes" you may need a different solution or a combination of solutions.
Those air coolers or swamp coolers as they are sometimes called, will only work in an area with very low humidity. They use what is called "evaporative cooling" to achieve a lower air temperature and while operating produce a lot of humidity. They will not produce air temperatures that are as cold as an airconditioning unit but they will lower the room temperature somewhat.
About 55 years ago, my soon to be "father-in-law" bought one of these units for use in Pittsburgh, Pa. His unit could be filled with both ice and water. He turned it on and said, "look how cold the air is". Yes, it was cold but the walls had streaks on them from the water that was condensing and running down the walls. Enough said!