Quick MoM Cost Analysis with Cost Comparison in AWS Cost Explorer

This blog post was made better by Amey Dhavle, Senior Product Manager, AWS

As organizations scale cloud usage, understanding cost variations becomes increasingly complex. Many of you have told us that you sometimes had to spend hours analyzing why costs changed from one month to another. To address this, we’re excited to announce a new cost comparison feature in AWS Cost Explorer that provides automated month-over-month cost change analysis. This feature enables you to quickly identify, understand, and explain variations in your AWS spending. With this new feature, you can now pinpoint the largest cost changes across any cost dimension, such as services, accounts and regions, and drill down into detailed explanations of these changes, including shifts in usage patterns, changes in commitment-based discounts, and applied credits within seconds. Now let’s take a look at this feature.

Use Case 1: Analyzing Month-over-Month Cost Changes

A rapidly growing technology startup faced the challenge of understanding substantial changes in their monthly AWS bills. Using the new Cost Comparison feature, they compared their June and July 2024 expenses to identify which services were driving the most significant cost variations. They configured the analysis to group costs by service and examine unblended costs for a clear view of gross spending before discounts.

Step 1: Access Billing and Cost Management Console

Open the AWS Billing and Cost Management console

Look at the new Top Trends widget. This widget provides a quick overview of your most significant cost changes between the previous two months. It shows the top 10 cost variations, sorted by absolute dollar difference, and displays both percentage and absolute value changes. The top trend widget highlights specific services, accounts, or regions where changes occurred, and it allows you to choose any trend to analyze it further in Cost Explorer’s Compare view. To dive deeper into your cost trends, view the Top trends widget on your Billing and Cost Management Home Page.

Step 2: Discovering Cost Trends

When the startup’s FinOps team accessed the AWS Billing and Cost Management console, they immediately noticed cost changes in the new Top Trends widget. The widget highlighted an increase in Redshift costs – an increase of $385,621.82 (189.87%) between April and May 2025.

The Top Trends widget also revealed other significant changes:

• Amazon OpenSearch Service showed a decrease of $279,957.68 (↓ 14.69%)
• Amazon EC2-Instances costs increased by $278,768.72 (↑ 19.81%)
• Amazon ElastiCache showed a notable increase of $202,698.06 (↑ 65.8%)

Step 3: Diving Deeper into Redshift Cost Changes

Intrigued by the significant Redshift cost increase, the team clicked on the “Redshift costs increased” link in the Top Trends widget. This took them to Cost Explorer’s new Compare view for a detailed analysis.

In the Compare view, they:

1. Confirmed the time range comparison (April 2025 vs May 2025)
2. Kept the default “Service” dimension to focus on Redshift
3. Viewed the detailed breakdown of what drove this cost increase

The automated analysis revealed:

• Changes in usage patterns across different instance types
• Increased upfront fees for RDS Reserved Instances
• Impact of applied discounts

The “View all” button in the top right corner allowed the team to explore additional cost drivers beyond these top three changes.

Use Case 2: Drilling down to a specific cost driver

Using the Compare view’s filtering capabilities, the team wanted to understand what drove the cost increase for a specific instance, the team clicked on the “+$65,360.49” link in the Top Trends widget. This took them to new tab for a detailed analysis.

In the new tab view, they:

1. Confirmed the time range comparison (April 2025 vs May 2025)
2. Kept the default “Service” dimension to focus on Redshift
3. Usage type was set to the selected instance
4. Viewed the detailed breakdown of what drove this cost increase for this specific instance

The automated analysis revealed:

• This was a new workload with no prior month spend
• Impact of applied discounts

From this point, they could further examine usage patterns in specific accounts that were using this instance and dive deeper into the cost drivers using the filters at their disposal

You can also leverage the AWS Cost Explorer API to programmatically perform similar cost comparisons and analysis across your organization. The API enables you to build custom cost management solutions, automate cost analysis workflows, and integrate cost data into your existing tools and dashboards.

Conclusion

The cost comparison feature in AWS Cost Explorer simplifies the complex task of understanding cloud cost variations. By automating the analysis process, it helps you:

1. Quickly identify significant cost changes
2. Understand the underlying drivers of these changes
3. Make data-driven decisions about your cloud spend

We’re excited to see how you’ll use Cost Comparison to gain deeper insights into your AWS costs. To learn more, check out our documentation or explore the API Reference.