C3X vs Terraform Cloud Cost Estimation

Terraform Cloud's cost estimation in context

HashiCorp added cost estimation to Terraform Cloud (now HCP Terraform) as a Team/Business tier feature. After terraform plan runs, TFC computes an estimated monthly cost delta and displays it in the plan output.

The feature has merit but has well-documented limitations:

• Resource coverage is partial: many common resources fall back to "$0/month estimated"
• Pricing data is updated periodically, not in real-time
• Requires the Team tier of TFC (additional per-user cost)
• Available only inside TFC — not in CI, not in a CLI
• No offline mode, no air-gapped support
• OpenTofu users can't access this feature at all

Where TFC cost estimation wins

• Already integrated: If you use TFC and the Team tier already, cost estimation appears with no setup. Zero friction.
• Native plan output: Cost data appears alongside terraform plan output in the same UI.
• HashiCorp-maintained: For teams that prefer a single-vendor stack, having TFC handle this means one less tool to evaluate.

Where C3X wins

• Resource coverage: C3X supports 80+ Terraform resources across AWS/Azure/GCP with detailed pricing dimensions. TFC's coverage is documented in their feature list and is notably narrower.
• Runs anywhere: C3X is a CLI you can use in GitHub Actions, GitLab CI, Bitbucket, Atlantis, Spacelift, local dev, or anywhere else. TFC cost estimation only runs in TFC.
• Offline / air-gapped: Critical for GovCloud, IL5/IL6, regulated industries. TFC requires the SaaS endpoint.
• OpenTofu support: Post-BSL license change, many orgs moved to OpenTofu. C3X works identically with both.
• Terragrunt support: Native Terragrunt integration.
• Cost recommendations: C3X suggests right-sizing, gp2-to-gp3, Spot conversions. TFC just shows the estimate.
• Free: Apache 2.0, no per-user fees.
• Self-hostable pricing API: For teams that want to control the pricing data fully.

Feature comparison

Using C3X with Terraform Cloud

If you use TFC for state and plan execution, you can still use C3X as a separate CI step. Common pattern:

# .github/workflows/terraform.yml
jobs:
  terraform:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
      - uses: c3xdev/c3x-action@v1
      - name: Estimate cost delta
        run: c3x estimate --diff --format=github-comment > c3x.md
      - name: Comment cost on PR
        uses: actions/github-script@v7
        with:
          script: |
            const fs = require('fs');
            github.rest.issues.createComment({
              issue_number: context.issue.number,
              owner: context.repo.owner,
              repo: context.repo.repo,
              body: fs.readFileSync('c3x.md', 'utf8')
            });
      - name: Run Terraform plan via TFC
        uses: hashicorp/tfc-workflows-github/actions/create-run@v1

C3X comments cost delta on the PR. TFC continues to handle state, plan execution, and apply. The two work together without conflict.

When to use which

Use C3X: You want broad resource coverage. You use OpenTofu or Terragrunt. You need offline mode. You're on TFC Free or HCP Free and need cost estimation. You want cost recommendations alongside estimates.

Use TFC's built-in: You're already paying for Team tier and only need basic coverage. You prefer a single-vendor stack. You don't need offline or OpenTofu support.

FAQ

Related reading

• How to estimate AWS costs from Terraform
• Budget guardrails in CI: blocking PRs that exceed cost limits
• C3X vs Infracost