OpenCost: The Ultimate Open Source Cloud Cost Monitoring Tool for Kubernetes

OpenCost: The Ultimate Open Source Cloud Cost Monitoring Tool for Kubernetes & Multi-Cloud Environments

OpenCost: The Ultimate Open Source Cloud Cost Monitoring Tool for Kubernetes & Multi-Cloud Environments

Cloud cost management is one of the biggest challenges facing DevOps and platform engineering teams today. With workloads spread across AWS, Azure, GCP, and even on-premise hypervisors, understanding where your money goes is nearly impossible without the right tool.

OpenCost — a CNCF incubating project — is the leading open-source solution for real-time Kubernetes and cloud cost monitoring. In this blog, we break down how OpenCost works, how it tracks costs across every major cloud provider, how it handles non-popular hypervisors, and how you can try it yourself with a live demo.

What is OpenCost?

OpenCost is a vendor-neutral, open-source (Apache 2.0) cost monitoring tool originally built by Kubecost and contributed to the CNCF. It provides:

  • Real-time cost allocation by Kubernetes cluster, namespace, pod, node, controller, and service
  • Multi-cloud cost monitoring for AWS, Azure, GCP, Oracle Cloud (OCI), and more
  • Dynamic on-demand pricing via cloud billing API integrations
  • On-premise and private hypervisor support via custom pricing
  • Carbon cost tracking for environmentally-conscious teams
  • A Prometheus /metrics endpoint for custom dashboards
  • MCP (Model Context Protocol) server for AI/LLM agent integration
  • A full REST API and a CLI (kubectl-cost)

How OpenCost Tracks Costs for Each Cloud Provider

OpenCost uses a two-layer approach: real-time on-demand pricing and cloud billing API reconciliation.

AWS (Amazon Web Services)

  • Integration: Uses the AWS Price List API and the AWS Cost and Usage Report (CUR)
  • Mechanism: OpenCost fetches on-demand instance pricing in real-time. For accurate cost data, it ingests the CUR from S3 buckets and reconciles against negotiated discounts and reserved instances
  • Coverage: EC2, EBS, EKS control plane, Load Balancers, Data Transfer, and more

Azure (Microsoft Azure)

  • Integration: Uses the Azure Retail Rates API and Enterprise Agreement (EA) billing data
  • Mechanism: Fetches real-time retail rates for VM sizes, storage, and networking. Supports EA and MCA (Microsoft Customer Agreement) billing for post-discount reconciliation
  • Coverage: Virtual Machines, Managed Disks, AKS, Load Balancers, and Public IPs

GCP (Google Cloud Platform)

  • Integration: Uses the Google Cloud Billing API and BigQuery export
  • Mechanism: Fetches SKU-based pricing from the Cloud Billing Catalog API. For actual cost, ingests BigQuery usage export data with committed-use discounts and sustained-use discounts applied
  • Coverage: Compute Engine, GKE, Persistent Disks, Cloud Storage, and Networking

OCI (Oracle Cloud Infrastructure)

  • Integration: Uses OCI Cost Analysis API
  • Mechanism: Fetches cost data from OCI’s cost analysis service for compute, storage, and networking resources
  • Coverage: OKE (Oracle Kubernetes Engine), Compute instances, Block Volumes

Other Providers (Alibaba, OVHcloud, Open Telekom Cloud, Scaleway)

OpenCost provides configuration pages and community-supported integrations for:
- Alibaba Cloud (documentation in progress)
- OVHcloud
- Open Telekom Cloud (OTC)
- Scaleway (documentation in progress)

These follow similar patterns of billing API integration or custom pricing overrides.

This is where OpenCost truly shines. Unlike vendor-specific tools, OpenCost is designed for heterogeneous infrastructure.

On-Premise / Bare Metal / Private Hypervisors

OpenCost supports on-premise Kubernetes clusters using a Custom CSV Pricing model:

  1. Default Pricing File (default.json): OpenCost ships with a default pricing configuration based on GCP us-central1 rates:
    json { "provider": "custom", "CPU": "0.031611", "spotCPU": "0.006655", "RAM": "0.004237", "GPU": "0.95", "storage": "0.00005479452", "zoneNetworkEgress": "0.01", "regionNetworkEgress": "0.01", "internetNetworkEgress": "0.12" }

  2. Custom Pricing Overrides: Users override these values via Helm values or a CSV file to match their actual negotiated hardware and data center costs:
    yaml opencost: customPricing: enabled: true costModel: CPU: 1.25 RAM: 0.50 storage: 0.25

  3. Hypervisor Agnosticism: OpenCost works with any hypervisor — VMware vSphere, Nutanix AHV, Proxmox, Xen, Hyper-V, KVM — as long as it runs Kubernetes. The cost model is applied at the node level based on the node’s resource capacity (CPU, RAM, GPU, storage), not the underlying hypervisor type.

  4. Prometheus-Based Metrics: OpenCost scrapes kube-state-metrics, node-exporter, and cAdvisor via Prometheus to get resource utilization. It then multiplies usage by the configured unit prices — regardless of whether the node runs on AWS, a VMware cluster, or bare metal.

  5. Cloud Cost Ingestion for Hybrid Setups: Even if your cluster runs on-prem, you can still use OpenCost’s Cloud Costs feature by configuring a cloud-integration.json secret to pull in external cloud service costs (e.g., RDS, S3, Datadog) alongside your on-prem Kubernetes allocations.

Use Case Example: VMware + Bare Metal + AWS Hybrid

A team running Kubernetes across a VMware vSphere cluster, bare metal servers in a colo, and AWS EC2 can use a single OpenCost deployment with:
- AWS billing integration for EC2/EKS nodes
- Custom pricing for the VMware and bare metal nodes
- Unified dashboard showing cost across all three environments

Live Demo

Experience OpenCost right now without installing anything:

👉 Live OpenCost Demo

The demo provides a fully functional OpenCost UI connected to a sample cluster with real allocation and cloud cost data. You can:
- Explore namespace-level and pod-level cost breakdowns
- View historical cost trends
- See asset inventory (nodes, disks, load balancers)
- Test the MCP server integration
- Experiment with the full REST API

OpenCost Architecture (High Level)

┌─────────────────────┐
│   Kubernetes API    │
│  (kube-state-metrics)│
└─────────┬───────────┘
          │
          ▼
┌─────────────────────┐
│     Prometheus      │
│ (metrics scraping)   │
└─────────┬───────────┘
          │
          ▼
┌─────────────────────────────────────┐
│        OpenCost Allocation Engine     │
│  ┌───────────────────────────────┐  │
│  │  Cost Model (pricing config)   │  │
│  │  ┌─────┐ ┌──────┐ ┌──────┐  │  │
│  │  │AWS  │ │Azure │ │ GCP  │  │  │
│  │  │ APIs│ │ APIs │ │ APIs │  │  │
│  │  └─────┘ └──────┘ └──────┘  │  │
│  │  ┌──────────────────────┐   │  │
│  │  │ On-Prem/Custom CSV   │   │  │
│  │  └──────────────────────┘   │  │
│  └───────────────────────────────┘  │
└────────────────┬────────────────────┘
                 │
                 ▼
┌───────────────────────────────────────┐
│     Outputs                           │
│  ┌────────┐ ┌────────┐ ┌───────────┐ │
│  │ REST   │ │Metrics │ │ MCP       │ │
│  │ API    │ │/metrics│ │ Server    │ │
│  └────────┘ └────────┘ └───────────┘ │
│  ┌────────┐ ┌────────┐               │
│  │ UI     │ │CLI     │               │
│  │ (React)│ │(kubectl)│              │
│  └────────┘ └────────┘               │
└───────────────────────────────────────┘

FAQ

What is OpenCost?

OpenCost is a vendor-neutral, CNCF incubating open-source project for measuring and allocating Kubernetes and cloud infrastructure costs in real-time.

Is OpenCost free to use?

Yes. OpenCost is licensed under Apache 2.0 and is completely free and open source.

What cloud providers does OpenCost support?

AWS, Azure, GCP, OCI (Oracle Cloud), OVHcloud, Open Telekom Cloud, with community support for Alibaba and Scaleway.

Can OpenCost work with on-premise or bare metal clusters?

Absolutely. OpenCost supports on-prem clusters via a Custom CSV pricing model. You define the unit prices for CPU, RAM, GPU, and storage, and OpenCost handles the rest.

Does OpenCost work with VMware, Nutanix, Proxmox, or other hypervisors?

Yes. OpenCost is hypervisor-agnostic. As long as Kubernetes runs on top of it, OpenCost can assign costs based on node resource capacity. It does not need native hypervisor integration.

How does OpenCost get pricing data?

For public cloud providers, OpenCost calls the cloud provider’s billing/pricing APIs (AWS Price List, Azure Retail Rates, GCP Billing Catalog). For on-prem, it uses user-defined CSV or Helm override pricing.

What is the difference between OpenCost and Kubecost?

OpenCost is the open-source cost allocation engine. Kubecost is a commercial product built on top of OpenCost that adds features like governance, alerting, savings recommendations, and enterprise support.

How do I get started?

Install via Helm in minutes:

helm repo add opencost https://opencost.github.io/opencost-helm-chart
helm repo update
helm install opencost opencost/opencost

Or try the live demo.

Does OpenCost support carbon cost tracking?

Yes. OpenCost includes carbon cost estimation for cloud resources, helping teams track their environmental impact alongside financial costs.

Can I use OpenCost from the command line?

Yes. OpenCost provides kubectl cost — a kubectl plugin — and a full REST API for programmatic access. It also has an MCP server for AI/LLM tool integration.

Tags

#OpenCost #Kubernetes #CloudCost #FinOps #CostOptimization #OpenSource #CNCF #AWS #Azure #GCP #OCI #DevOps #SRE #MultiCloud #OnPrem #VMware #Kubecost #Prometheus #MCP #CostMonitoring

Conclusion

OpenCost is the gold standard for open-source cloud cost monitoring. Whether you are running on AWS, Azure, GCP, OCI, a private VMware cluster, or bare metal in a colo, OpenCost gives you a single pane of glass for understanding your Kubernetes spend.

With its CNCF backing, MCP server for AI integration, rich API surface, and completely free licensing, OpenCost is the smart foundation for any FinOps strategy.

Try it now: https://demo.infra.opencost.io
GitHub: https://github.com/opencost/opencost
Documentation: https://www.opencost.io/docs/

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