The City of Ljubljana and some of its public institutions and companies have this year also joined the Earth Hour, an international environmental initiative.

On Saturday, 28 March, 2015, between 8.30 and 9.30 pm, the following objects were covered in dark:
- Ljubljana Castle,
- Plečnik's Arcades at the Ljubljana Market,
- lights at the Plečnik's Žale, which light the Plečnik's Propylaea,
- lights at the walls of the Križanke,
- the LPP administrative building exterior,
- the Energetika Ljubljana public company has turned off lights at the administrative building on Verovškova Street 62 and the exterior parking lighting,
- the VO-KA public company has turned off the exterior of the administrative building on Vodovodna Street 90,
- the Javni Holding company turned off the lights at Verovškova Street 70.

Earth Hour is a global initiative against environmental change organized by the World Wide Fund for Nature Australia (WWF) in 2007. Today, the Earth Hour is a global movement with Ljubljana participating in it for the fourth consecutive year.