The electrician, if he is worth his salt, can size and recommend a contactor/enclosure. I have bought them on Amazon in the $10 to $30 range and mounted them in metal boxes in the same neighborhood of price. You are probably looking at $20 to $50 for the parts.
By the way, if you intend to monitor the power consumption with the POW then the contactor method will not work. The AC load current will be passing through the contactor. The POW will only see the tiny amount of power needed to energize the coil. You may as well just use a Basic.
Yes and no. You can remotely lock it off but there will be no way to know if the unit is actually running since you can't see the power consumption. All you will know for sure is whether the power to it is available for operation. In other words you can see if the contactor is open or closed but not whether someone actually turned the unit on.
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Unless we are talking about a large AC system or the rare window unit with an internal contactor that is about all I have to offer. With a system that already contains a control circuit it might be possible to integrate a Sonoff or Sonoff SV inside the unit itself or the thermostat.
One other thought that just occurred to me is that if the unit you are controlling has an electronic control instead of the old mechanical switch and thermostat you might be "up the creek". When you remove and apply power to those things they are initially in an "OFF" state and require button pushes to turn on. Of course an electronic control might lend itself to a Sonoff simulating a button push if you are willing to hack into it a bit.
If it is electronic the Sonoff isn't going to turn it on. When power is applied the initial state is off and requires a button push.
If it were me I would look at some of the wi-fi enabled AC remotes like the Switchbot.
Apparently my other message to you was not approved. Amazon has a DEWENWILS Outdoor Smart Wi-Fi Outlet Box, Heavy Duty 40A 120VAC 2HP Wireless Controller Timer Switch for Pool Water Heater SPA, Compatible with Smart Phone, Alexa, UL Listed. This appears to be a Wi-Fi switch and contactor built into a nice box for $69.00. If you are not willing to spend that then you are probably out of luck.
Again, this will not turn the unit on but if you want to limit the times that it can be turned on this will do that.
My comments keep getting blocked.
Search for "Outdoor Smart Wi-Fi Outlet Box" on the world's biggest online retailer site. The $69.99 item you find looks interesting.
PJ
I bought a SonOff pow R2 to work with my 220V A/C Unit . My electrician says it cant work because our 220 V system uses 2 input wires but the sonoff only uses 1. he said something about it being a europpean system being different. What can he do to work around it?