As measuring from where and how? That'll depend on the mainboard used, how many PCIe slots you have/enabled, what type of SSD, whether the SSD is directly attached or through an HBA, how many power supplies are connected at a given time, how much system loads are induced on it, whether the loads are CPU bound or IO bound, how is it attached (ethernet/IB/serial/USB/etc), etc. That's kinda like asking how much gas does a Boeing 777-300ER burn in the sky - the answer is always "it depends".
