terraci cost

Estimate monthly AWS costs by analyzing plan.json files in module directories.

Usage

terraci cost [flags]

Flags

Flag	Short	Type	Default	Description
--module	-m	string		Estimate cost for a specific module
--output	-o	string	text	Output format: text, json

How It Works

1. Scans the working directory for plan.json files (output of terraform show -json plan.tfplan)
2. Detects the region from the module path using the configured structure.pattern
3. Fetches AWS pricing data from the Bulk Pricing API (cached locally)
4. Matches each resource to a cost definition and calculates monthly estimates
5. Outputs per-module cost with before/after/diff

No AWS credentials required — pricing data is public.

Examples

# Estimate all modules
terraci cost

# Single module
terraci cost --module platform/prod/eu-central-1/rds

# JSON output (for scripts/CI)
terraci cost --output json

# Verbose — shows per-resource breakdown and cache info
terraci cost -v

Output

Text (default)

platform
  prod
    eu-central-1
      vpc                                     monthly: $120.50  diff: +$64.80
        aws_nat_gateway.main                  monthly: $32.40   az: eu-central-1a
        aws_eip.nat                           monthly: $3.60
      eks                                     monthly: $450.00
        aws_eks_cluster.main                  monthly: $73.00
summary
  modules                                     count: 3
  total                                       before: $570.50  after: $635.30  diff: +$64.80

JSON

terraci cost --output json

{
  "modules": [
    {
      "module_id": "platform/prod/eu-central-1/rds",
      "before_cost": 0,
      "after_cost": 689.12,
      "diff_cost": 689.12,
      "resources": [
        {
          "address": "aws_db_instance.postgres",
          "monthly_cost": 400.77,
          "price_source": "aws-bulk-api"
        },
        {
          "address": "aws_lambda_function.worker",
          "monthly_cost": 12.04,
          "price_source": "usage-based",
          "status": "usage_estimated",
          "status_detail": "usage-based estimate derived from provisioned concurrency"
        },
        {
          "address": "aws_sqs_queue.jobs",
          "monthly_cost": 0,
          "price_source": "usage-based",
          "status": "usage_unknown"
        }
      ]
    }
  ],
  "total_before": 0,
  "total_after": 762.12,
  "total_diff": 762.12,
  "currency": "USD"
}

status is present for every resource result:

• exact means TerraCi found a plan-time price
• usage_estimated means TerraCi derived a partial estimate from configured capacity
• usage_unknown means cost is still unknown at plan time
• unsupported / failed may also include failure_kind and status_detail

Prerequisites

• At least one provider opted in (e.g. extensions.cost.providers.aws.enabled: true) in .terraci.yaml

Pricing Cache

AWS pricing data is cached via the diskblob blob-store backend to avoid repeated API calls:

• Default location: project's service directory (.terraci/blobs/cost/pricing/) — diskblob's root_dir setting overrides it (default ~/.terraci/blobs)
• Default TTL: 24 hours — override via extensions.cost.blob_cache.ttl
• Cache status shown in terraci cost output: expires_in=23h49m or status=expired

See Also

• Cost configuration — enable and configure cost estimation
• terraci summary — posts costs in MR/PR comments
• examples/cost-estimation — working example