Understanding Savings Plans in Stax
AWS Savings Plans are financial mechanisms used to reduce your AWS bill by offsetting the cost of compute usage. Savings plans are similar to Reserved Instances in that they both discount your AWS bill based on expected AWS compute usage. Like a Reserved Instance, a Savings Plan represents a commitment to an amount of AWS usage over a one- to three-year period, but at a discounted price.
How Savings Plan Charges Appear in AWS Billing
Savings plans are represented in your AWS bill in three different ways. First, the savings plan line item which represents the amortized cost of the savings plan that you have purchased. Second, you will see credits applied to your bill as a result of the savings plan. Lastly, you'll see the additional field SavingsPlanEffectiveCost for each item. Read this section to see how those items are calculated.
The Savings Plan Line Item
A Savings Plan will come through to your bill as a Savings Plan line item. This line item will be the cost of your Savings Plan. As we know the cost of a savings plan is the financial commitment over the period that you purchased the plan. If you purchased a Savings Plan over a year period you would see the cost of this purchase amortized over the year. These charges are reflected in your bill daily (this only applies to Savings Plans that are purchased with no upfront cost).
To see your Savings Plan costs, open the Data page in Stax and filter the kind field to show records of type savings_plan. This will filter the data to only show your savings plan charges for the given month. By default, when searching over multiple months, results are aggregated across all months. Group by Interval to show charges aggregated by month.
The Credits Line Item
A Savings Plan is a commitment to an amount of compute usage over a period of time. Any "savings" created from purchasing a Savings Plan are applied through the mechanism of a credit for the savings plan discount. The credit applied to your account will be the daily value of the applied Savings Plan discount. This means two things:
-
On your bill you are charged for EC2 instance usage and then credited the amount that is covered under your Savings Plan.
-
The credit can be zero if you are not using any compute that is covered by your Savings Plan.
To see the credits that you are receiving from your Savings Plan discount go to the data page and add a filter to the "Usage code" field of savings_plan_discount. This will filter the data to only show you the Savings Plan discount credits applied to your account.
The Savings Plan Effective Cost
The Savings Plan effective cost is how AWS represents how these savings plan discounts are applied on an instance level. This means that for an EC2 instance you have the unblended cost (the cost without any discounts applied) and the savings plan effective cost. The Savings Plan effective cost is the cost of an instance with the hourly discount price applied to it. This distinction is important to see the true reflection of how your Savings Plan impacts your instance costs.
It is important to note that in usage mode, Stax will use the Savings Plan's effective cost, so that you see a true reflection of your instance "usage".
An Example
In the below example you can see that later in the month, charges for the Savings Plan start being applied. At this point you'll be begin to be charged the amortized cost of your Savings Plan (this charge occurs whether you are using your Savings Plan or not).
On a specific day, the charges for the EC2 instance spend may break down as follows:
-
You're being charged for the Savings Plan you purchased.
-
A portion of your EC2 spend is covered by your Savings Plan and thus receive the discount of the Savings Plan (this can range from 66% to 75% depending on the plan). It's important to remember that EC2 spend does not equate to EC2 instances.
-
You're given a credit (a negative charge) for the instance spend that is covered by the Savings Plan. This is your "Savings Plan discount".
-
Any EC2 spend not covered by your Savings Plan is charged at the standard on-demand rate. This can be the remaining (25%-33%) or additional EC2 spend beyond what is covered.
The Savings Plans page
Understanding Savings Plans terms will help you better use and understand the Stax Savings Plans page. For a more detailed guide on AWS Savings Plans, please refer to AWS Savings Plans documentation.
Key Terms
Eligible usage: Eligible usage refers to any AWS usage costs that receive a discount because they are covered by Savings Plans. AWS offers a number of different Savings Plan types, each applying to different service usage:
-
Compute Savings Plans apply to usage across Amazon EC2, AWS Lambda, and AWS Fargate
-
EC2 Instance Savings Plans apply to EC2 usage
-
SageMaker Savings Plans apply to Amazon SageMaker usage
On-Demand Usage: The AWS public unblended on-demand cost of usage. Savings Plans are charged at a discounted rate which is determined by the term, commitment amount and Savings Plan type.
Commitment: The agreed hourly usage, for example, $0.001/hour, you commit to spend in exchange for a lower price when purchasing a Savings Plan.
Covered Usage: The AWS service usage covered by the Savings Plan Commitment. This usage will be charged at a discounted rate.
Uncovered Usage: When you exceed the Savings Plans commitment, you have uncovered usage that is charged at the on-demand rate.
Recurring Savings Plan monthly fees: The recurring hourly charges that correspond to No Upfront or Partial Upfront Savings Plans.
Amortized Upfront Plan monthly fees: The upfront Savings Plan fee that corresponds to All Upfront or Partial Upfront Savings Plans amortized over the month.
Overview Panel
The Overview panel shows the following metrics related to your Savings Plans:
-
Account: The AWS Account ID where the Savings Plan was purchased.
-
Savings Plan ID: The unique Savings Plan identifier.
-
Type: The Savings Plan type such as Compute, EC2 Instance, or SageMaker.
-
Instance Family: The instance family, such as M5, C5, R5, T3a, etc, that the Savings Plan is committed to. This is only applicable to EC2 Instance Savings Plans. Savings Plans that apply to more than one Instance family will have a value of Multiple. Where there is no eligible usage on a Savings Plan, the instance family will be shown as None.
-
Region: The AWS Region the Savings Plan is committed to. This is only applicable to EC2 Instance Savings Plans.
-
Status: The status of the Savings Plan, either Active, Queued, or Retired.
-
Term: The Savings Plan commitment term in months, this can be either 12 months or 36 months.
-
Start: The Start date of the Savings Plan commitment. Hover over the Start date in the panel to see the Savings Plan start date and time in UTC.
-
End: The End date of the Savings Plan commitment. Hover over the End date in the panel to see the Savings Plan end date and time in UTC.
-
Payment Option: The payment option of the Savings Plan, such as All Upfront, Partial Upfront, or No Upfront.
-
Utilization: The percentage of Savings Plan commitment that was covered by eligible usage over the selected time period.
-
Total Commitment: The total amortized upfront and recurring spend commitment associated with your Savings Plan over the selected time period.
-
Used Commitment: The Savings Plan commitment amount that was used over the selected time period.
-
Net Savings: The amount saved using Savings Plans commitments over the selected time period, compared to the AWS On-Demand cost.
Utilization Panel
The following scenarios explain how Utilization data is calculated in Stax:
Scenario 1: Fully utilized EC2 Savings Plan
| Savings Plan monthly commitment | $150/month |
|---|---|
Utilisation $Eligible Usage Covered by Savings Plan | $150 |
Utilisation %Eligible Usage/Commitment | 100% |
*Scenario 2: Underutilized EC2 Savings Plan
| Savings Plan monthly commitment | $150/month |
|---|---|
Utilisation $Eligible Usage Covered by Savings Plan | $120 |
Utilisation %Eligible Usage/Commitment | 80% |
Cost Panel
The following scenarios explain how Cost data is calculated in Stax:
Scenario 1
SP term: 12 months
Payment Option: No Upfront
Hourly Commitment: $0.40
Upfront fee: $0
Recurring monthly fee: $290
| Fee Type | Charges (Unblended) | Amortized Cost over the SP Term (12 months) |
|---|---|---|
| Upfront fee | $0 (month 1) | $0 per month |
| Recurring monthly fee | $290 per month | $290 per month |
Scenario 2
SP term: 12 months
Payment Option: Partial Upfront
Hourly Commitment: $0.40
Once off Upfront fee: $1800
Recurring monthly fee: $142
| Fee Type | Charges (Unblended) | Amortized Cost Over the SP Term (12 months) |
|---|---|---|
| Upfront fee | $1800 (month 1) | $150 per month |
| Recurring monthly fee | $142 per month | $142 per month |
Scenario 3
*SP term:*12 months
Payment Option: All Upfront
Hourly Commitment: $0.40
Upfront fee:$3500
Recurring fee:$0
| Fee Type | Charges (Unblended) | Amortized Cost Over the SP Term (12 months) |
|---|---|---|
| Upfront fee | $3500 (month 1) | $292 per month |
| Recurring monthly fee | $0 per month | $0 per month |
Notes
-
All unblended charges and amortized costs are prorated based on the Savings Plan start date, end date, and the number of days in each month.
-
Calculations are based on hourly commitments and fee rates
On-Demand Spend Equivalent Panel
The following table explains how the public On-Demand Spend Equivalent is derived:
| Example 1 | Example 2 | Example 3 | |
|---|---|---|---|
| On-Demand Rate | $0.00150/hour | $0.00129/hour | $0.0052/hour |
| Savings Plan Rate | $0.00100/hour | $0.00100/hour | $0.0026/hour |
| Covered Usage | 720 hours | 360 hours | 100 hour |
Unblended CostOn-Demand Rate * Covered Usage | $1.08 | $0.464 | $0.52 |
Savings Plan Effective CostSavings Plan Rate * Covered Usage | $0.72 | $0.360 | $0.26 |
| On-Demand Spend Equivalent | -$1.08 | -$0.464 | -$0.52 |
When viewing your costs on the Data Page, the On-Demand Spend Equivalent is shown as a Credit under the Savings Plan ARN and Usage code field of savings_plan_discount.
When viewing your CUR data in AWS, the Equivalent On-Demand Spend is represented as Savings Plan line item type of Savings plan Negation.
Savings Panel
The following table explains how Savings Plan savings are calculated:
| Scenario 1 | Scenario 2 | Scenario 3 | Scenario 4 | |
|---|---|---|---|---|
| On-Demand Rate | $0.0072/hour | $0.00150/hour | $0.00129/hour | $0.0052/hour |
| Covered Usage | 720 hours | 0 hours | 720 hour | 360 hours |
Unblended CostOn-Demand Rate * Covered Usage | $5.18 | $0.00 | $0.93 | $1.87 |
| Savings Plan Payment Option | All Upfront | Partial Upfront | No Upfront | No Upfront |
| Savings Plan Rate (Commitment) | $0.0056/hour | $0.00100/hour | $0.00100/hour | $0.0026/hour |
Savings Plan Usage CostSavings Plan Rate * Covered Usage | $4.03 | $0.00 | $0.72 | $0.93 |
| Savings Plan Amortized Upfront & Partial Upfront Fee | $4.03 | $0.41 | $0.00 | $0.00 |
| Savings Plan recurring Fee | $0.00 | $0.31 | $0.72 | $1.87 |
Savings Plan Net Savings(Unblended Cost - (Savings Plan Amortized Upfront & Partial Upfront Fee + Savings Plan recurring Fee) | $1.15 | -$0.72 | $0.21 | $0.00 |
Scenario 1: The customer has fully utilized the Savings Plan commitment and has benefited from the lower Savings Plan usage rate. As this is an All UpfrontSavings Plan, the all upfront cost is amortized to calculate the monthly savings amount.
Scenario 2: The customer has incurred a negative savings amount due to not having utilized any of their Savings Plan commitment, however they are still required to pay the Savings Plan fees which have resulted in a loss.
Scenario 3: The customer has fully utilized the Savings Plan commitment and has benefited from the lower Savings Plan usage rate. As this is aNo Upfront Savings Plan*,*the recurring monthly fee amount is used to calculate the savings amount.
Scenario 4: The customer has partially utilized the Savings Plan commitment. Although they have benefited from the lower Savings Plan usage rate, in this case, the on-demand unblended cost for the covered usage hours equates to the same amount as the recurring monthly Savings Plan fee amount.