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Data Transfer Charges - Billing Reports inconsistent

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I have an EC2 instance which hosts my backend application - catering to requests of my frontend which is hosted not on AWS. And I also have a RDS instance which is in the same VPC and is privately connected to the EC2 instance. Now, I have using AWS before with similar traffic and similarly configured application. Also, I have SSL certification on my EC2 instance, and this is connected to a custom domain. I recently, specially from March 1st 2025, started getting charged for Data Transfer on EC2, but looking at the billing report of the DataTransfer service, I can see some inconsistencies -

  1. In the month of march, when I look at Cost Explorer, I have incurred charges only from March 17th, but the billing report sent by the billing support team suggests that I have it from March 1st. Not only this, on 1st march, at 12:00:00 AM it went from incurring 0 charges being in 100GB free limit - '$0.000 per GB - data transfer out under the monthly global free tier', to directly '$0.086 per GB - <my local region>data transfer to ,<some other region>' costing me 0.0000194257 dollars. Now, when I see the usage when it still was in Free tier, it is just 0.00002355 GB, and not 100GB. What would have caused this descripency when all I have is a simple java application running, with low traffic.
  2. In April too. I see in the billing report that the same PublicIp-Out operation incuring charge on the April 1st 12:00:00 AM, but I got the mail for DataTransfer limit crossing 85% of Free Tier resource on 15th of April, after which I shut down my Ec2 instance to stop any kind of charge. I don't see I have any charges yet, but the billing report is simply not consistent.

I would appreciate any kind of help with this. Thanks.

Topics
Cloud Financial ManagementComputeJava DevelopmentAWS Free Tier
Tags
AWS Cost ExplorerAmazon EC2AWS BillingJava DevelopmentAWS Free Tier
Language
English
Kanchan
asked a month ago54 views
2 Answers
0

There are a few potential explanations for the inconsistencies you're seeing in your data transfer charges:

  1. Timing discrepancies: The difference between Cost Explorer and the billing report could be due to how data is processed and when it becomes available in different AWS billing tools. Cost Explorer may have a slight delay in showing the most recent data.

  2. Free tier usage: The AWS Free Tier typically includes 100 GB of outbound data transfer aggregated across all services. It's possible that you exhausted this limit earlier than expected, perhaps due to usage from other AWS services. The sudden jump from free tier to charged usage could occur if you hit this limit.

  3. Inter-region data transfer: The charge you're seeing for data transfer between regions ($0.086 per GB) suggests that some of your traffic is moving between different AWS regions. This is typically more expensive than data transfer to the internet and is not covered by the free tier.

  4. Billing granularity: AWS often bills in hourly increments, which could explain why you see charges starting precisely at midnight.

  5. Public IP charges: Starting from February 2024, AWS began charging for public IPv4 addresses. This new charge could be contributing to what appears to be unexpected data transfer costs.

To address these issues and get a clearer picture of your usage:

  1. Use AWS Cost Explorer with finer-grained filters to break down your usage by service, usage type, and time period.

  2. Check for any resources in other regions using EC2 Global View.

  3. Verify that you don't have any lingering resources like EBS volumes or snapshots from terminated instances.

  4. Consider using CloudWatch to monitor your NetworkIn and NetworkOut metrics for a more detailed view of your data transfer.

  5. If you're still unsure about the charges, it's best to open a support case with AWS for a detailed investigation of your account's usage and billing.

Remember that data transfer charges can be complex, especially when dealing with inter-region transfers and public IP usage. Optimizing your architecture to minimize data movement between regions and to the internet can help reduce these costs.

Sources
Data Transfer Charges | AWS re:Post
Discrepancy in Lightsail Data Transfer Out Charges Despite Below-Allowance Usage | AWS re:Post
Unexpected billing because of EC2, VPC, and Data Transfer | AWS re:Post

profile picture
re:Post Agent
answered a month ago
AWS
EXPERT
AWS Support - Marc
reviewed a month ago
  • Kanchan
    a month ago

    From the list of potential explanations, for few points below are the explanations

    1. Time discrepency - The support team has notified me about the gap of 24 hours which it takes usually to update the records. It still doesn't make sense for the month of April, the free tier limit on the Cost and Usage Analysis > Free Tier section, for the Data Transfer seems to have reached only 92 GB and not have crossed 100GB limit as suggested by the billing report. And I don't see any cost for that as well. Even if this is a normal issue in Billing tools, it doesn't change the descrepancy in the data provided.

    2. and 4. 100 GB is a lot to be exhausted in even 1 hour given the user and event count on my application - which I track through analytics services, which is only in 100s in a day. So I don't see how granularity affects this issue of exhausting all the resources (and mind you the usage in the report still is less than 100GB before it incuring a positive charge which is still not explained).

    3. I checked in the EC2 global view, there is no chargeable resource present in any other region. I just have these in other regions - single VPCs, some subnets, single security groups. And that's it.

    4. On the EC2 service Free tier page it's mentioned that this is the part of free tier - "750 hours per month of public IPv4 address regardless of instance type". Now, the only public IPV4 address I am using is the one I got with EC2 instance by default as part of this free tier.

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Hi,

Since this is of a detailed billing and pricing nature, I'd suggest opening a support case directly with our Billing Support team. You can do so via this link: Billing Support.

They have the tools and may be able to really break this down for you.

-Dino C.

AWS
MODERATOR
AWS Support - Dino
answered a month ago

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