AWS CUR - Understanding Savings Plan and Reserved Instance Billing

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Went through the [https://wellarchitectedlabs.com/cost/300_labs/300_cur_queries/query_help/](AWS Well-Architected Labs) to under stand below line item types in our AWS CUR. I am having hard time understanding which field to query the actual cost to match with the invoice. Currently I am using below logic to calculate net cost payable, however, the numbers are not matching with the Invoice.

  1. DiscountedUsage [ using reservation_effective_cost to calculate the net cost payble ]
  2. SavingsPlanCoveredUsage [ savings_plan_savings_plan_effective_cost to calculate netcost payble]
  3. SavingsPlanNegation [ Negative numbers - considering the line items as 0 ]
  4. SavingsPlanRecurringFee [ Charged on 1st of every month, using line_item_blended_cost, because the savings_plan_savings_plan_effective_cost is 0 for all the line ietms]
  5. RIFee - [ line_item_blended_cost to calculate net cost payable ]
  6. Usage - [ line_item_blended_cost to calculate net cost payable ]
  7. Tax - [ line_item_blended_cost to calculate net cost payable ]

We have

  1. A 3 year no upfront savings plan option.
  2. No Discount Line Item
asked 8 months ago865 views
2 Answers
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Accepted Answer

Hello, Santosh Sahoo.

It looks like you are trying to understand how to calculate the net cost payable in your AWS Cost and Usage Report (CUR) by matching it with the invoice. Here's a breakdown of how to calculate each of the line item types you mentioned:

DiscountedUsage: To calculate the net cost payable for DiscountedUsage, you can use the reservation_effective_cost. This value represents the cost of AWS resources that are covered by Reserved Instances (RIs) or Savings Plans (SPs). It accounts for the discount provided by these commitments.

SavingsPlanCoveredUsage: For SavingsPlanCoveredUsage, you can use the savings_plan_savings_plan_effective_cost field. This field represents the cost of AWS resources covered by Savings Plans, considering the Savings Plans' effective discount. This is similar to DiscountedUsage but specific to Savings Plans.

SavingsPlanNegation: SavingsPlanNegation typically represents negative numbers and can be considered as zero cost because it represents situations where AWS provides you with credits or adjustments. In your calculation, you can treat this as 0 cost.

SavingsPlanRecurringFee: SavingsPlanRecurringFee represents the recurring fee charged for your Savings Plans. You can use the line_item_blended_cost for this, as you mentioned, because it is a straightforward cost.

RIFee: To calculate the net cost payable for RIFee (Reserved Instance fee), you can use the line_item_blended_cost. This field represents the cost of your Reserved Instances.

Usage: For Usage costs, you can also use the line_item_blended_cost. This field represents the cost of using AWS resources on a pay-as-you-go basis.

Tax: Tax line items typically represent additional taxes applied to your AWS charges. You can use the line_item_blended_cost to calculate the net cost payable for taxes.

Additionally, it's a good practice to reconcile your CUR with your AWS Billing and Cost Management dashboard.

Best regards, Andrii

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answered 8 months ago
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reviewed 2 days ago
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reviewed 2 months ago
  • To match CUR with monthly invoices, one should only use the SUM in the line_item_unblended_cost column, because invoices only show unblended cost (the cost the customer would pay on a monthly basis, instead of the amortized cost of the RIs/SPs that's spread across the whole term of the commitment)

  • Nice explanation, Andrii. However, I found that 'DiscountedUsage' only represents the cost of AWS resources covered by RIs (the cost covered by SPs is not included in this value) in AWS Data Exports User Guide (https://docs.aws.amazon.com/cur/latest/userguide/Lineitem-columns.html)

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To match what you see on the invoices, you ONLY should use line_item_unblended_cost. The "RI effective cost" or the "SP effective cost" does not get reflected on the invoice. Those charges are useful if you are trying to amortize the upfront cost of your RI or SP across the whole term considering how the discount applies to your usage throught the term of the commitment.

With the No Upfront RI or SP, you would not have any upfront charges. With All Upfront or Partial Upfront payment option, those upfront charges would get generated in a separate subscription invoice. To find your recurring monthly fee for RIs or SPs in CUR you would normally search for the column line_item_line_item_type and the values would be like 'RIFee' or 'SavingsPlanUpfrontFee'

So, effectively, if you wanted to match the cost of your invoices with the SUM of cost you see in CUR, for this purpose you should only use the line_item_unblended_cost column. Because invoices will display the unblended cost.

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answered 8 months ago
  • Thanks Nataliya. Appreciate your response. :)

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