Kubecost vs OpenCost: What the Difference Actually Is

OpenCost is the free, open-source CNCF project that measures Kubernetes spend and attributes it down to namespace, workload, and pod. Kubecost is IBM's commercial product built on top of that same engine, adding reconciliation against your real invoice, longer retention, recommendations, alerts, multi-cluster rollups, and support. Same core math underneath, different amount of product wrapped around it.

They are not competitors in the usual sense. Kubecost's engineers wrote the allocation engine, donated it to the CNCF as OpenCost, and kept building a commercial product on top. So the question is never which one is better at Kubernetes cost. The question is how much of the work you want to operate yourself.

What is OpenCost?

OpenCost is a vendor-neutral CNCF project that measures and allocates Kubernetes infrastructure cost in real time. It watches the cluster, prices the nodes, and splits that spend across namespace, deployment, service, label, and pod. It is Apache 2.0 licensed, free at any size, and you run it inside your own cluster alongside Prometheus.

It was accepted into the CNCF in June 2022 and moved to incubating status in October 2024. That status matters mostly as a signal: the project has published governance and a contributor base beyond one vendor. Engineers from Amazon, Google, Microsoft, Adobe, and SUSE were involved early.

What OpenCost gives you is the number, exposed through an API and a basic UI, and scrapeable into Prometheus and Grafana like any other metric. What it does not give you is opinions about the number. No savings recommendations, no anomaly alerts, no federated view across clusters, and nobody to call when it breaks.

Is Kubecost open source?

Partly, and this is the detail people get wrong most often. The allocation engine underneath Kubecost is open source, because that engine is OpenCost under Apache 2.0. The Kubecost product you install is commercial software owned by IBM, which acquired Kubecost in September 2024. It has a free tier, and free is not the same thing as open source.

The honest phrasing: Kubecost is built on open source and contributes to it heavily, and the product itself is proprietary with a generous free tier. If your requirement is an auditable, forkable, no-vendor-terms tool, that requirement points at OpenCost.

What is the difference between OpenCost and Kubecost?

Three differences carry almost all the weight. Everything else is detail you can work out after you have picked one.

Accuracy against your actual bill. OpenCost prices nodes at on-demand list rates by default. If you run reserved instances, savings plans, committed use discounts, spot capacity, or a negotiated enterprise discount, its numbers drift away from your invoice. Kubecost's central commercial pitch is reconciling allocation data against what you were actually charged, discounts included. For engineering visibility, list rates are usually good enough, because engineers care about the ratio between workloads, not the absolute dollar. For chargeback that finance signs off on, list rates are not good enough.

Retention. OpenCost keeps exactly as much history as your Prometheus keeps. That is both a feature and a chore, since sizing, paying for, and backing up that storage is now your job. Kubecost's free tier stops at 15 days of metric retention, which is enough to spot a trend and not enough to explain a quarter.

Everything surrounding the number. Recommendations, governance, alerting, federated multi-cluster views, a hosted platform, and support are the Kubecost side of the line. OpenCost's own FAQ says as much, which is a refreshingly clear product boundary.

Kubecost free tier limits

The free tier is called Foundations. It covers unlimited clusters up to 250 cores in total, with 15-day metric retention. Past 250 cores you are into paid tiers, which IBM quotes rather than lists publicly.

250 cores sounds roomy until you count your nodes. Ten 32-core machines is 320 cores, and that is one modest production node pool. Foundations comfortably covers a startup, a set of dev and staging clusters, or a pilot on one team's namespace. It runs out quietly right around the point where cost allocation starts to matter to someone outside engineering.

In practice the retention cap bites first. Fifteen days answers "what is expensive right now" and cannot answer "why was March worse than February," which is the question that actually gets asked in a budget review. If you want the history without the contract, exporting OpenCost metrics into a Prometheus you control is the free path.

Do I need Kubecost?

Only if you need something OpenCost does not do. If you run one or two clusters, mostly on-demand, and the goal is showing engineers what their namespace costs, OpenCost is the entire answer and it costs nothing. Reach for Kubecost when you need bill-accurate chargeback, rollups across many clusters, retention past two weeks, or a vendor who owes you a response.

The practical test is who will run it. OpenCost installs easily enough, but you own the Prometheus behind it, its storage, its upgrades, and its failures at 3am. If your team already has the habit and tooling to provision servers and roll out upgrades with zero downtime, one more Helm chart and a retention decision is a small addition. If your platform team is two people who are already underwater, paying someone else to keep the cost data alive is a defensible line item.

The second test is who reads the number. Engineers tolerate approximate numbers because they are comparing workloads against each other. Finance does not, because they are comparing your number against an invoice. The moment a controller is in the room, reconciliation stops being a nice-to-have.

What neither one sees

Both tools are good at Kubernetes, and for container-level attribution they are frequently the right choice. That is also the ceiling. Your clusters are one slice of the bill, and for most companies not the biggest one. Managed databases, object storage, data transfer, the control plane, load balancers, the observability vendor, and every SaaS seat you pay for all sit outside the cluster and outside both tools.

The failure I see repeatedly: a team stands up OpenCost, builds a genuinely nice dashboard, feels good, and total spend keeps climbing because the growth was in RDS and Datadog the whole time. Container attribution is a real problem worth solving, and solving it does not tell you what your technology spend is.

So pick one of these for the cluster, then pair it with something that covers the full invoice. Cross-cloud cost allocation across accounts and teams is a different job from per-pod attribution, and both are worth having. Our writeup on Kubecost and its alternatives goes into where each fits, and if you are still shortlisting, start by comparing cloud cost management tools against what you actually need to answer.

Frequently asked questions

Is OpenCost free?

Yes. OpenCost is Apache 2.0 licensed with no size limit, no core cap, and no license fee. Your only cost is the infrastructure it runs on plus the Prometheus storage behind it, and the engineering time to keep both healthy.

Who owns Kubecost?

IBM, which acquired Kubecost in September 2024 and folded it into its FinOps portfolio. OpenCost stays independent under CNCF governance, so the open-source engine does not belong to IBM even though IBM remains a major contributor to it.

Can I start with OpenCost and move to Kubecost later?

Yes, and that is a sensible sequence. Since Kubecost is built on the OpenCost engine, the allocation concepts, labels, and namespace model carry over. The migration cost is mostly redoing dashboards and alert routing, not relearning how cost gets attributed.

How to decide this week

Install OpenCost in one cluster. It takes an afternoon and it is free, and the numbers it produces will tell you whether allocation is even your problem. If the answer is that a handful of namespaces are wildly over-requested, you do not need to buy anything yet. You need to go fix the requests, which is where most of the money in Kubernetes cost optimization lives.

Only after that, look at what OpenCost cannot tell you: reconciled dollars, history past your retention window, one view across every cluster. If those gaps are real and someone outside engineering is asking about them, get a quote. If they are not, you already have your answer, and it was free.