[Coedy]

I believe grannies are ~2kw, Home charging points are 7kw. so just over 3x faster. If you wanted to most home chargers can be crippled down to 3.6kw to reduce strain on your house (if you run immersion heaters overnight and have an undersized house fuse for example).

The main reason to get a proper charger is the fact they are safer.
Most sockets arent designed to have that level of constant current draw for hours upon hours. If the socket itself isnt brand new then that is also likely worn and can add to the heat worries.

Granny Cable Compatibility?

So I had my granny cable melt the socket it was plugged into - socket somehow still works but can’t check the status of the cable due to melted plastic around the prongs. I wanted to know if it would be safe to use the granny cable provided by Tesla (for the model Y) to charge my Zoë?

www.speakev.com

There are plenty of reports of Granny chargers melting into the socket they are connected to. These were originally supplied as "in case of emergencies" not "save £800 and use this instead" however buying EVs is like the wild west where sales people still say anything they can to get a sale..

Many people use them fine without issues for years, Similar numbers get smoke, scorching or excess heat. I decided not to use mine overnight because I couldn't hold my hand onto the back of the plug casing for longer than 20seconds due to the heat after 4 hours of charging (and that's in a brand newly installed external socket).