Both Reserved Instances and Savings Plans exist to do the same basic thing: trade a commitment for a discount off pay-as-you-go pricing. Where they differ is what, exactly, you're committing to, and that difference matters more than most teams expect once real money is on the line.
The core tradeoff in one sentence
A Reserved Instance locks in a specific VM family in a specific region in exchange for a deeper discount. A Savings Plan locks in a dollar-per-hour spending level in exchange for flexibility across VM families, regions, and a few other compute services. Nearly everything else below is just detail on that one tradeoff.
What a Reserved Instance actually commits you to
- A 1-year or 3-year term, tied to a specific VM family in a specific region.
- A discount that can reach roughly 72% off pay-as-you-go at the 3-year term, and higher still, up to around 80%, when combined with Azure Hybrid Benefit on eligible Windows or SQL workloads.
- Some built-in flexibility: the reservation applies across an instance size flexibility group, so it isn't locked to one exact VM size, just the family and region.
- Cancellation is possible, but refunds are capped at $50,000 in a rolling 12-month window per billing profile, not unlimited.
Reserved Instances fit workloads that genuinely aren't moving: a database tier that's been the same shape for months, a backend service with no migration on the roadmap. The discount is only real if the commitment stays matched to actual usage.
What a Savings Plan actually commits you to
- A 1-year or 3-year term, but the commitment is a fixed dollar-per-hour spend, not a specific resource.
- The discount applies automatically across eligible compute, any VM family, any region, plus services like App Service, Container Instances, and Azure Functions.
- The discount tops out lower than Reserved Instances, typically around 65%.
- There's no cancellation path the way Reservations have one. That's the direct tradeoff for the added flexibility.
Savings Plans fit workloads that are still in motion: infrastructure that might resize, move regions, or shift shape over the commitment term, where locking in a specific VM family would be a bad bet.
Which one wins on discount depth
For a workload that truly isn't going to move, Reserved Instances win on pure discount depth, roughly 72% versus 65% at a 3-year term, which is a meaningful gap once real spend is behind it. When both a Reservation and a Savings Plan could apply to the same resource, Azure applies the Reservation discount first, since it's the deeper one.
The catch: that gap only holds if the commitment stays matched to real usage. A Reservation sitting against a VM family nobody runs anymore isn't a discount, it's a sunk cost that keeps billing regardless. (Discount figures here reflect typical current Azure pricing structure and are worth confirming against Azure's own pricing page, since exact rates can shift by region and VM family.)
The layered strategy most mature teams land on
In practice, this usually isn't either-or. A common pattern:
- Reserved Instances on the steady-state layer, the part of the footprint that's been flat for months with no signs of changing.
- Savings Plans on the flexible layer, always-on infrastructure that might still shift shape.
- Pay-as-you-go left for anything genuinely bursty or seasonal, where committing at all would be premature.
This is also why commitment coverage is worth tracking as an ongoing number, not a one-time purchase decision. The right split between the three layers changes as the workload changes underneath it.
What neither one covers
Both mechanisms are compute-focused. Storage, bandwidth, and a lot of platform-level charges sit entirely outside either one. A team that's fully optimized on compute commitments can still watch its bill climb from data egress or storage tier choices that neither Reservations nor Savings Plans touch at all.
One more edge case worth knowing: Savings Plans generally aren't available in sovereign or government cloud environments. Reserved Instances are, though with a smaller eligible VM portfolio there. Not relevant to most teams, but worth knowing if it applies to yours.
A simple decision checklist
- Has this workload's shape been stable for a few months, same VM family, same region? Lean toward a Reserved Instance.
- Is it still actively changing, or could it move regions or families within the term? Lean toward a Savings Plan.
- Is it bursty or seasonal rather than always-on? Leave it on pay-as-you-go, don't commit yet.
- Revisit the split at least quarterly. Coverage that made sense two quarters ago often doesn't anymore.
Working out this split by hand means cross-referencing usage history against two different commitment mechanics, then checking back regularly as workloads shift. CloudNomix's commitment coverage view tracks this continuously and flags underused commitments directly, so the question isn't "which did we buy," it's "is what we bought still the right call."