Cinergy: Deterministic Power Monitoring for Carbon Accounting in the Cloud

Cloud providers now commonly offer tools to monitor the environmental impact of hosted services, aiming to inform customers about the carbon footprint of their infrastructures. A significant share of this impact arises from the power consumption of servers. To allocate server-related emissions, these methodologies typically rely on resource-quantity-based attribution and do not account for the effective usage of virtual resources. We demonstrate that resource usage can drastically affect carbon estimations. This article proposes a framework, called Cinergy, to standardize how cloud providers integrate the power consumption of virtual resources into their carbon calculators. It defines a baseline to deterministically assess the power consumption of a provisioned Virtual Machine (VM) - i.e., the same usage should yield the same power estimate - while still accounting for consolidation gains enabled by virtualization. Our approach, constructed and evaluated empirically, achieves high precision, with a mean absolute error of 6.6% across various hardware. Using metrics collected from cloud providers, we reveal the impact of instance type on energy efficiency, with differences reaching 85% for the same VM size. We also show that quantity-based carbon accounting methodologies can drastically underestimate actual CO₂ emissions - by up to a factor of three.