This paper describes a system to support the development and assessment of methodologies that explore the energy flexibility provided by electric water heaters. The proposed system follows a modular approach and allows users to share and remotely control the referred devices. The operation of this system is presented in this paper considering a case study where the energy flexibility provided by a 100 L electric water heater is used to reduce electricity costs under the Portuguese tariff context. The collected results reveal that increasing the available energy flexibility leads to larger savings. These results also show that the referred savings depend on the instant associated to hot water consumption events.