Native, open source and commercial
AWS cost optimisation tools, compared honestly
Most of this category sells dashboards. Dashboards are useful once somebody has decided what to do; they are not a substitute for that decision. Here is what each tier of tool is genuinely for.
Start with the free AWS tools, because they cover more than people expect: Cost Explorer for where the money goes, Compute Optimizer for rightsizing, Cost Anomaly Detection for surprises, Trusted Advisor for the obvious orphans, and Storage Lens for S3. Add an open-source scanner such as Komiser or the Cloud Custodian ruleset if you want continuous checks. Commercial platforms are worth paying for above roughly $50,000 a month of spend, or when several teams need chargeback. Below that, the tool is rarely the constraint.
Free, from AWS
| Tool | What it is genuinely good at | Where it stops |
|---|---|---|
| Cost Explorer | Where the money goes, by service, usage type, tag and region. Grouped by usage type it answers most questions. | No resource IDs without the Cost and Usage Report, and no opinion about what to do. |
| Compute Optimizer | EC2, EBS, Lambda and ECS-on-Fargate rightsizing with a risk rating. Free and accurate. | Under-recommends without memory metrics, which means installing the CloudWatch agent. |
| Cost Anomaly Detection | Machine-learning alerts on unusual spend. Ten minutes to set up, free. | Reactive. It tells you about the new problem, not the old one. |
| Trusted Advisor | Idle load balancers, unassociated addresses, low-utilisation instances. | Full cost checks need Business or Enterprise support. |
| Cost Optimization Hub | Aggregates recommendations from several AWS sources into one list with estimated savings. | Recommendations only. Still nobody’s job to action them. |
| S3 Storage Lens | Free tier shows storage by class, non-current versions and incomplete multipart uploads across the account. | S3 only, and the useful metrics are in the paid tier for older data. |
| Cost and Usage Report | The complete record, down to resource ID and hour. Everything else is a view over this. | Needs S3 plus Athena or QuickSight to be usable, and a day to start delivering. |
Open source
| Tool | What it does | Worth it when |
|---|---|---|
| Cloud Custodian | Policy-as-code across AWS: find, tag, notify and remediate on a schedule. | You want enforcement rather than reporting, and you have someone to own the policies. |
| Komiser | Inventory and cost visibility across accounts, self-hosted. | You want a dashboard without a per-seat contract. |
| Infracost | Shows the cost delta of a Terraform change in the pull request. | You use Terraform. This is the best place in the whole workflow to catch cost, before it exists. |
| AWS Nuke | Deletes everything in an account. | Ephemeral sandbox accounts only. Genuinely dangerous anywhere else. |
Commercial platforms
| Category | What you are buying | Where the value threshold sits |
|---|---|---|
| Visibility and allocation platforms | Unit economics, chargeback by team and product, Kubernetes cost splitting, anomaly alerting. | Multiple teams sharing accounts, or a finance function that needs per-customer cost. |
| Automation platforms | Continuous rightsizing, commitment management, automatic scheduling. | Enough scale that continuous beats periodic, and enough trust to let software act. |
| Commitment brokers | Buy and resell commitments so you get discount without the lock-in. | Large, predictable spend where the flexibility is genuinely worth a share of the saving. |
| Consultancies and audits | A person who looks at your account and tells you what to do about it. | When the constraint is attention rather than information. |
The uncomfortable part
Nearly every tool in this category, including the free AWS ones, produces a list of recommendations. Very few accounts are short of recommendations. What they are short of is somebody whose job it is to work through them, and no dashboard fixes that.
Most commercial platforms price as a percentage of spend or per seat, which means the cost scales with the problem rather than with the work. Below roughly $50,000 a month, the annual licence is frequently a large share of the saving it identifies, and the free AWS tools would have identified most of the same things.
We sell an audit, so treat that as a declared interest. The honest version is that if you have someone who will spend a day a month on this, the free tools plus the checklist on this site will get you most of the way. If you do not, buying software will not create that person.
The one tool almost nobody installs and should
Infracost, in the pull request. It is the only tool in this list that prevents cost rather than reporting it, and preventing a $400 a month resource from being created is worth more than finding it eighteen months later.
Put numbers on it
Frequently asked questions
What is the best free AWS cost optimisation tool?
Compute Optimizer, by a distance, because it makes a specific recommendation with a risk rating instead of showing you a graph. Enable it, install the CloudWatch agent so it can see memory, and give it a fortnight of data. Cost Explorer grouped by usage type is the best free tool for understanding a bill; Compute Optimizer is the best one for changing it.
Do I need a third-party cost platform?
Below about $50,000 a month, usually not. The free AWS tools cover visibility and rightsizing, and the gap is attention rather than data. Above that, or when several teams share accounts and need chargeback, allocation becomes a real problem that AWS-native tooling handles poorly, and a platform earns its price.
Are open-source cost tools good enough?
For enforcement, Cloud Custodian is genuinely excellent and is used at large scale in production. For visibility, the open-source dashboards are fine and usually behind the commercial ones on Kubernetes allocation. The real cost of open source here is that somebody has to run it, and that person is usually the same person who does not have time to action the recommendations.
How does an audit differ from running these tools?
Overlap on the automatable checks, and difference on the judgement ones. A tool tells you an instance averages 4% CPU. It cannot tell you that the instance is memory-bound and correctly sized, or that the log group with no retention is the one your auditor asks about every year. Our audit runs about seventy automated checks and then a person verifies every finding before it reaches the report, which is the part software does not do.
Keep reading
Prices checked against AWS list rates on 2 August 2026. AWS changes prices; treat every figure here as a close approximation rather than a quote.
£499 fixed. Free scan first. 20%+ found or it’s free.
The scan is read-only — a role you create and delete, no keys shared — and shows your estimated monthly saving before anyone talks about money.