AWS EC2 Instance Compute Saving plan

A simple post here might not cover the full spectrum of AWS cost optimization, but I will focus on the details. If you want to dive deeper into all aspects of Cost Optimization I recommend the AWS Well Architected Labs for Cost Optimization: https://www.wellarchitectedlabs.com/cost/

First some basics:

• You mention 300 GByte of Storage. This is not important here, as Savings Plans only apply to the Compute part of EC2, not the Storage part.
• Please make sure to book the savings plan in the right account. This can be the account where the instance resides or the Organization Management account, if Savings Plan Sharing is turned on.

EC2 Instance Savings Plans are specific to a region, operating system, tenancy, and instance family. So make sure you purchase your savings plan in the correct region.

Next you need to decide if you want to commit to a 1 year or 3 years savings plan. The 3 years Savings Plan provides a higher discount but is also comes with the higher risk that you pay for a service you won't use if you decide to stop the instance after the 1st year.

Finally you need to decide on a payment method: Do you want to pay for the runtime of the Savings Plan fully upfront? In this case you make a one-time payment at the beginning with no follow-up costs. The other extreme is no upfront, where the cost of the savings plan is spread monthly across the runtime. A model in between is partially upfront, where you pay one part on-time at the beginning, followed by a monthly fee.

Once you have decided on all these factors you open the AWS Cost Management Console and select Savings Plans. You click on Purchase Savings Plan , select the option EC2 Instance Savings Plan. In this screen you select the runtime, the region, and the instance family.

Now you have to define the hourly commitment. In this field you have to put in the already discounted rate. You can use this calculator to get the necessary values: https://aws.amazon.com/savingsplans/compute-pricing/.
Let's assume you run your t3.xlarge instance in us-east-1 and decided on a 3-year runtime with no upfront payment. The on-demand price for this instance is 0.1664 USD/hour (as of today, public pricing), the Savings plan run rate is 0.0719 USD/hour, which is a discount of 57% over on-demand.

If you enter this price as hourly commitment and select the same payment option. It will give you a price of 52.49 USD/month.

Optionally you can select a start date, which is handy if you want to renew a Savings Plan before expiration.

Finally you add the Savings plan to the shopping cart and finalize the purchase.

You can purchase a Compute Savings plan on your own via the EC2 Dashboard within the AWS console. Compute Savings Plans provide the most flexibility and help to reduce your costs by up to 66% (similar to Convertible RIs). These plans automatically apply to any EC2 instance usage regardless of region, instance family, operating system, or tenancy–including those that are part of EMR, ECS, or EKS cluster.

That being said, if you plan to only use an EC2 Instance and not other compute services like ECS, EKS, etc., check out the EC2 Savings Plan. EC2 Instance Savings Plans apply to a specific instance family within a region and provide the largest discounts, up to 72% (similar to Standard RIs). This plan covers the usage of all instance types, regardless of size, within the same region for that chosen family (e.g., M5 usage in N. Virginia).

Savings Plans can be purchased on a Payer Account in consolidated org, if no resources are running on the Payer, Savings Plan will first apply to the usage that offers highest discount. Savings Plan can also be applied at each child account instead of payer.

If your having issues with the purchase, feel free to reach out to Amazon Support for assistance.