It would be unwise to throw an old air conditioning window unit in the trash, as it contains freon and other refrigerants that would be harmful to the environment. These substances in the air conditioning unit that help cool you off are regulated by the government by the Clean Air Act.
It’s also a good idea to replace window units after a while (and before they stop working at critical moments). The older an ac unit is, the harder it has to work, which can cause your energy bills to increase. They can become a breeding ground for germs and mold. Central air units are also incredibly expensive to fix, and upgrading before it’s too late keeps your home’s value up.
When it’s time to replace your air conditioning unit, as previously stated, you don’t want to just put on the curb for the garbage truck. Think about what specialty companies can come pick it up. Furthermore, parts of the ac unit can be recycled, which is always a good idea to create more sustainable products. If it’s not that old, you can even donate it to someone in need (please just make sure it’s clean and still has life in it).