The problem

Some teams avoid containers fearing overhead. Measurements show Docker adds slightly more energy than bare metal, mostly from I/O virtualisation, but packing workloads onto fewer machines usually outweighs it.

The fix you can use today

• Consolidate containers onto fewer, busier nodes.
• Avoid unnecessary layers of virtualisation (containers inside VMs inside VMs).
• Shut down nodes the bin-packing frees up.

A study found that Docker adds only a little energy compared with running on the bare machine. GreenCode's research review draws on this work.

Tools that help

• Kepler: exports energy estimates per pod and container on Kubernetes, using eBPF and hardware counters
• Scaphandre: measures the power drawn by each process on a Linux server and exports it to Prometheus and other monitoring stacks

How GreenCode helps

GreenCode helps tackle this by mining a running estate, rebuilding it as infrastructure as code and tracing energy and CO2e to the services that cause it, including services barely running at all. More on this.

Tags

#docker#kubernetes#right-sizing

Sources

• GreenCode State of the Art Review, D2.1 (2025), PDF p. 126: Docker adds a slight increase in energy vs bare metal due to I/O virtualisation, usually outweighed by consolidation (Santos et al. 2018)
• Green Software Foundation, Green Software Patterns: containerise your workloads

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