UPDATE: It looks like if your Model Y Premium in the U.S. has the newer Power Conversion System (PCS2), then your vehicle is capable of Vehicle-To-Load (V2L). If your Model Y Premium doesn't, your car is not capable of V2L.
You can check if your car has it by putting in your VIN number into Tesla's parts catalog and typing in "assembly power conversion." One of the two pages will have a label "Original VIN Part," and that's how you tell which version you have:
parts.tesla.com/en-US/landin…
You can also just check Tesla's Outlet Adapter accessory page in the Tesl app and it will tell you if your car is compatible, although it seems that page still needs to be updated for some people.
Tesla has officially launched Vehicle-To-Load (V2L) capability for all Model Y Premium trims in the U.S.
This means that you can now use your vehicle’s battery and the Tesla Outlet Adapter to power other devices and appliances including space heaters, power tools, camping gear, fans, etc, with Tesla's $80 Outlet Adapter.
It's also now live on Tesla's online vehicle configurator (second pic below), and it lets you select the adapter during the config process. Since there is no "only Model Ys produced as of" date listed for the capability, presumably all Premium Model Ys have this V2L capability, but I will let you know if I hear anything different.
Outlet Adapter Specs:
• 120V, 20A
• 2.4kW max power
• Gen 3 Mobile connector required