A window AC or Window Air Conditioner is worth it.
However it's more efficient to use a central air conditioner if you're trying to cool down the entire house.
But if you just want to cool down 1 or 2 rooms then using a window AC to cool down those rooms will be cheaper than using the central air conditioner.
But if you need to run 3 to 4 window air conditioners at the same time to cool down an entire house then the window ac will use more electricity and not be able to cool down the house properly.
Window AC units are meant to be used as a supplement to the central air conditioner or for cooling down a small house or a few bedrooms.
I'm mostly in my home office working online and when I'm home alone I turn down the central air conditioner and use my window air conditioner to just cool down the home office.
I don't need the whole house cooled down when I'm working in my home office so I just use the window air conditioner and it saves me money.
I only run the central air conditioner when it's more than just me at home or I have family over or friends.
A window air conditioner uses around $20.00 to $30.00 per month in electricity costs while a central air conditioner can use as much as $200.00 to $300.00 per month.