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AWS Billing and Cost Management
User Guide (Version 2.0)

Accessing Reserved Instance Recommendations

If you enable Cost Explorer, you automatically get Amazon EC2, Amazon RDS, ElastiCache, Amazon ES, and Amazon Redshift Reserved Instance (RI) purchase recommendations that could help you reduce your costs. RIs provide a discounted hourly rate (up to 75%) compared to On-Demand pricing. Cost Explorer generates your RI recommendations using the following process:

  • Identifies your On-Demand Instance usage for a service during a specific time period

  • Collects your usage into categories that are eligible for an RI

  • Simulates every combination of RIs in each category of usage

  • Identifies the best number of each type of RI to purchase to maximize your estimated savings

For example, Cost Explorer automatically aggregates your Amazon EC2 Linux, shared tenancy, and c4 family usage in the US West (Oregon) Region and recommends that you buy size-flexible regional RIs to apply to the c4 family usage. Cost Explorer recommends the smallest size instance in an instance family. This makes it easier to purchase a size-flexible RI. Cost Explorer also shows the equal number of normalized units so that you can purchase any instance size that you want. For this example, your RI recommendation would be for c4.large because that is the smallest size instance in the c4 instance family.

Cost Explorer recommendations are based on a single account or organization usage of the past seven, 30, or 60 days. Cost Explorer ignores usage that is already covered by an RI. Amazon EC2, ElastiCache, Amazon ES, and Amazon Redshift recommendations are for RIs scoped to Region, not Availability Zones, and your estimated savings reflects the application of those RIs to your usage. Amazon RDS recommendations are scoped to either Single-AZ or Multi-AZ RIs. Cost Explorer updates your recommendations at least once every 24 hours.

Note

Cost Explorer doesn't forecast your usage or take forecasts into account when recommending RIs. Instead, Cost Explorer assumes that your historical usage reflects your future usage when determining which RIs to recommend.

Linked accounts can see recommendations only if they have the relevant permissions. Linked accounts need permissions to view Cost Explorer and permissions to view recommendations. For more information, see Viewing the Cost Explorer Reservation Recommendations.

RI Recommendations for Size-Flexible RIs

Cost Explorer also considers the benefits of size-flexible regional RIs when generating your RI purchase recommendations. Size-flexible regional RIs help maximize your estimated savings across eligible instance families in your recommendations. AWS uses the concept of normalized units to compare the various sizes within an instance family. Cost Explorer uses the smallest normalization factor to represent the instance type that it recommends. For more information, see Instance Size Flexibility for EC2 Reserved Instances.

For example, let’s say you own an EC2 RI for a c4.8xlarge. This RI applies to any usage of a Linux/Unix c4 instance with shared tenancy in the same region as the RI, such as the following instances:

  • One c4.8xlarge instance

  • Two c4.4xlarge instances

  • Four c4.2xlarge instances

  • Sixteen c4.large instances

It also includes combinations of EC2 usage, such as one c4.4xlarge and eight c4.large instances.

If you own an RI that is smaller than the instance that you're running, you are charged the prorated, On-Demand price for the excess. This means that you could buy an RI for a c4.4xlarge, use a c4.4xlarge instance most of the time, but occasionally scale up to a c4.8xlarge instance. Some of your c4.8xlarge usage is covered by the purchased RI, and the rest is charged at On-Demand prices. For more information, see How Reserved Instances Are Applied in the Amazon Elastic Compute Cloud User Guide.

Viewing the Cost Explorer Reservation Recommendations

Linked accounts need the following permissions to view recommendations:

  • ViewBilling

  • ViewAccount

For more information, see Billing and Cost Management Permissions Reference.

To view your RI recommendations

  1. Sign in to the AWS Management Console and open the Billing and Cost Management console at https://console.aws.amazon.com/billing/home#/.

    The console opens to the Dashboard, where you can see your current month-to-date usage graphs.

  2. In the navigation pane, choose Cost Explorer.

  3. On the Cost Explorer page, choose Launch Cost Explorer.

  4. On the navigation bar, choose the menu. Under Select a service, choose the service that you want recommendations for. The default recommendation is for RIs with a one-year term and a payment option of Partial Upfront (based on your previous seven days of usage).

Reading the Cost Explorer RI Recommendations

At the top of the RI recommendation page there are three numbers: your Estimated Annual Savings, your Savings vs. On-Demand, and your Purchase Recommendations. Your Estimated Annual Savings is how much Cost Explorer calculates that you could save by purchasing all the recommended RIs. Your Savings vs. On-Demand is your estimated savings as a percentage of your current costs. Your Purchase Recommendations is how many different RI purchase options that Cost Explorer found for you. The pane on the right has four parameters that control which settings Cost Explorer uses to generate your recommendations.

At the bottom of the page are three savings estimates. The table shows the different purchase recommendations and details about the recommendations. If you want to see the usage that Cost Explorer based a recommendation on, choose the View Usage in Cost Explorer link in the recommendation details. This takes you to a report that shows the exact parameters that Cost Explorer used to generate your recommendation. The report also shows your costs and associated usage grouped by Purchase Option, so that you can view the On-Demand Instance usage that your recommendation is based on.

You can sort your recommendations by Monthly Estimated Savings, Upfront RI Cost, Purchase recommendation, or Instance Type.

Modifying Your RI Recommendations

You can change the information that Cost Explorer uses when it creates your recommendations, and you can also change the types of recommendations that you want. This allows you to see recommendations for the RIs that work best for you, such as All UpFront RIs with a one-year term, based on your last 30 days of usage.

Note

Instead of forecasting your future usage, Cost Explorer assumes that your future usage is the same as your previous usage. Cost Explorer also assumes that you are renewing any expiring RIs.

To modify your RI recommendations

  1. Sign in to the AWS Management Console and open the Billing and Cost Management console at https://console.aws.amazon.com/billing/home#/.

    The console opens to the Dashboard, where you can see your current month-to-date usage graphs.

  2. In the navigation pane, choose Cost Explorer.

  3. On the Cost Explorer page, choose Launch Cost Explorer.

  4. On the navigation bar, choose the menu, choose RI Recommendations and then under Select a service choose the service that you want to modify the recommendations for.

  5. In the RI Recommendation Parameters pane, change the parameters that you want to change. Your estimated savings update automatically.

    1. For RI term, select the RI term that you want.

    2. For Offering class, select the RI class that you want.

    3. For Payment option, select the purchase option that you want.

    4. For Based on the past, select how many days of usage that you want your RI recommendations to be based on.

Saving Your RI Recommendations

You can save your RI recommendations as a CSV file.

To save your RI recommendations

  1. On the Reserved Instance Recommendations page, in the parameter pane, change the parameters that you want to change. Your estimated savings update automatically.

  2. Above the recommendation table, choose Download CSV.

The CSV file contains the following columns.

RI Recommendation CSV Columns

Column Name

Service

Column Explanation

Recommendation Date

EC2, RDS, RS, ELC, ES

The date that Cost Explorer generated your recommendation.

Owner Account

EC2, RDS, RS, ELC, ES

The account associated with your recommendation.

Instance Type

EC2, RDS, ES

The type of instance that the recommendation is generated for (for example, m4.large or t2.nano). For size-flexible recommendations, Cost Explorer aggregates all usage in a organization (for example, the m4 family) and shows a recommendation for the smallest instance type RI that is available for purchase (for example, m4.large).

Node Type

ELC, RS

The type of node that the recommendation is generated for, such as ds2.xlarge.

Size Flexible Recommendation

EC2, RDS

Whether a recommended RI is size-flexible.

Max hourly usage in Historical Period

EC2, RDS, RS, ELC, ES

The maximum number of instance hours used in an hour over the period chosen for generating recommendations.

Min hourly usage in Historical Period

EC2, RDS, RS, ELC, ES

The minimum number of instance hours used in an hour over the period chosen for generating recommendations.

Average hourly usage in Historical Period

EC2, RDS, RS, ELC, ES

The average number of instance hours used per hour over the period chosen for generating recommendations.

Max hourly normalized unit usage in Historical Period

EC2, RDS

The maximum number of normalized units used in an hour over the period chosen for generating recommendations.

Min hourly normalized unit usage in Historical Period

EC2, RDS

The minimum number of normalized units used in an hour over the period chosen for generating recommendations.

Average hourly normalized unit usage in Historical Period

EC2, RDS

The average number of normalized units used per hour over the period chosen for generating recommendations.

Projected RI Utilization

EC2, RDS, RS, ELC, ES

How much of the recommended RI Cost Explorer estimates you will use.

Location

EC2, RDS, RS, ELC, ES

The region of the instances used to generate a recommendation. You must purchase the recommended RIs in the recommended region to see potential savings.

Tenancy

EC2

The tenancy for the recommended RI purchase. Valid values are shared or dedicated.

OS

EC2

The operating system and license model for the recommended RI instance type.

Term

EC2, RDS, RS, ELC, ES

The recommended term length for the recommendation.

Payment Option

EC2, RDS, RS, ELC, ES

The recommended payment option for the recommendation.

Recurring Monthly Cost

EC2, RDS, RS, ELC, ES

The recurring monthly cost of the recommended reservations.

Recommended Instance Quantity Purchase

EC2, RDS

How many reservations Cost Explorer recommends that you buy.

Recurring Monthly Cost

EC2, RDS, RS, ELC, ES

The recurring monthly cost of the recommended reservations.

Recommended Normalized Unit Quantity Purchase EC2, RDS, RS, ELC, ES

How many normalized units that Cost Explorer recommends that you buy.

Break Even Months

EC2, RDS, RS, ELC, ES

The estimated length of time before you recoup your upfront costs for this set of recommended reservations.

Database Edition RDS The edition of the database engine that the recommended RDS reserved instance runs.
Database Engine RDS The kind of engine that the recommended RDS RI runs, such as Aurora MySQL or MariaDB.
Cache Engine ELC The kind of engine that the recommended ElastiCache reserved node runs, such as Redis or Memcheched.
Deployment Option RDS Whether your RI is for an RDS instance in a single Availability Zone or an RDS instance with a backup in another Availability Zone.

Using Your RI Recommendations

To purchase the recommended reservations, go to the purchase page on a service console. You can also save a CSV file of your recommendations and purchase the reservations at a later date.

To use Amazon Elastic Compute Cloud recommendations

  1. On the Reserved Instance Recommendations page, choose Amazon EC2 RI Purchase Console to go to the Amazon EC2 Purchase Console.

  2. Purchase your RIs by following the instructions at Buying Reserved Instances in the Amazon EC2 User Guide for Linux Instances.

To use Amazon Relational Database Service recommendations

  1. On the Reserved Instances page in the Amazon RDS console, choose Purchase Reserved DB Instance.

  2. Purchase your reservations by following the instructions at Working with Reserved DB Instances in the Amazon RDS User Guide.

To use Amazon Redshift recommendations

  1. On the Reserved Node page in the Amazon Redshift console, choose Purchase Reserved Nodes.

  2. Purchase your reservations by following the instructions at Purchasing a Reserved Node Offering with the Amazon Redshift Console in the Amazon Redshift Cluster Management Guide.

To use Amazon Elasticsearch Service recommendations

  1. On the Reserved Instances page in the Amazon ES console, choose Purchase Reserved Instance.

  2. Purchase your reservations by following the instructions at Amazon Elasticsearch Service Reserved Instances in the Amazon Elasticsearch Service Developer Guide.

To use Amazon ElastiCache recommendations

  1. On the Reserved Cache Nodes page in the ElastiCache console, choose Purchase Reserved Cache Node.

  2. Purchase your reservations by following the instructions at Purchasing a Reserved Node in the Amazon ElastiCache User Guide.