You Do Need power plug adapter while traveling from Antigua and Barbuda to Saint Lucia.

Here is Why You Need An Adapter

The outlet and plug type used in Saint Lucia is G and in Antigua and Barbuda are A and B. This is how they look like.

Antigua and Barbuda

In Antigua and Barbuda, outlets of type A and B are in use.

Type A

Type B

Saint Lucia

In Saint Lucia, outlets of type G are in use.

Type G