Ensuring Specific Power

I want to switch the AC on/off only if the power flowing through is in specific boundaries.

Say if 100W fan is plugged in, it doesn't work, but a vacuum at 1000W does. Similarly it should cut of if it exceeds 1500W.

I have 220V AC, which I was thinking to turn on/off with a relay connected to arduino, but how can you ensure these power boundaries?

Let’s say you start with nothing plugged in. That’s below your “100W” cutoff.

Now plug in a 1000W load. How does it magically get from 0W to 1000W without passing through 100W along the way?

I’m guessing you’d need a time delay to allow the 1000W device to get up above the threshold. But then a 100W load will turn off and on all the time because you can’t measure what current the device is going to pull until it’s actually pulling current.

Have you researched any power sensors that will interface to the Arduino? Safe isolation from the 220V supply is a big issue but I’m sure there are modules out there that will do this for you relatively safely.

flowupon: I want to switch the AC on/off only if the power flowing through is in specific boundaries.

Say if 100W fan is plugged in, it doesn't work, but a vacuum at 1000W does. Similarly it should cut of if it exceeds 1500W.

I have 220V AC, which I was thinking to turn on/off with a relay connected to arduino, but how can you ensure these power boundaries?

Your question doesn't make sense to me. How are you going to switch on the power "in specific boundaries", since the power is zero when its switched off, you have no knowledge of the power of your load.

Please explain better what you are actually trying to do, this might be the xyproblem again.