Lights in homes and businesses around the world will be switched off tonight marking Earth Hour.

People are being encouraged to flick the switch for one hour from 8.30.

The event's now in its ninth year and encourages people to think and do more about saving the planet.

Spokesperson Suds Sarronwala says an unprecedented 172 countries and territories have confirmed their participation.

"The lights out of course are a visual shoutout. It stays as the punctuation if you will, but it stays as the trigger for things throughout the year."

Suds Sarronwala says the aim is to empower people to take concrete actions.

"173 countries and territories around the world, we estimate that there are going to be more than 7000 cities, and every single continent is going to participate."