Best answer by aaronr
At full tilt the fans can be about as loud as a cooker hood fan on a medium setting, but even in summer this hasn't occurred for me under normal use.
The only time I've ever seen it this loud is if the charger ever needs to be turned off at the fuse -- when it reboots it seems to do a fan test at 100% for 5 seconds or so.
When the charger is idle, the fans are off, and generally only kick in when it's charging your car at full speed -- I've not noticed the fans running while the car is exporting (although it might). When the fans do run, as others have said they're about as loud as an average computer fan or a quiet fan oven. From inside the house I can't hear it, and I have only noticed it when I've been stood next to the charger while outside of the house.
Hope this helps!