With a continuous increase in their electricity consumption, data centres (DCs) represent nowadays, as well as for the whole Information and Communication sector, a considerable environmental impact. The number of applications and services hosted in the cloud is significant, and the associated number of infrastructure is steadily increasing. Cloud Service Providers need to respond to this growing demand and size their infrastructures accordingly. But users expectations in terms of service quality as well as their misbehaviour lead to oversized infrastructures, resulting in poor resource utilization and additional power consumption. To address these issues, various techniques such as virtualization, shutdown techniques, elasticity or consolidation enable improved energy efficiency of Cloud infrastructures. But as their behaviour can increase DC energy consumption and environmental footprint, users can also help reducing them. In this paper, we study how users provided with a simple tool can reduce the power consumption of a virtualization cluster in a cloud company. Using a Virtual Machine (VM) shutdown policy, users can directly contribute to the mitigation of the power consumption of the infrastructure. Part of the paper is dedicated to profile the users and understand their behaviour when it comes to powering off their VMs. To further reduce the energy consumption of the cluster, we combine the VM shutdown policy with a simple consolidation heuristic. Simulations show a 23.95% power consumption reduction, with an additional 8.72% reduction thanks to the users. A production implementation was conducted and results in a 12.58% power consumption reduction over one week.