Reserved Instances vs Savings Plans — Which Saves More? (2026 Guide)

Both Reserved Instances and Savings Plans trade a 1- or 3-year commitment for a big discount over on-demand pricing. The difference is flexibility versus a slightly deeper discount — and the mistake most teams make isn't picking the wrong one, it's under-using the commitment they already bought.

up to 72%

off on-demand with a commitment

Compute SP

most flexible: EC2 + Fargate + Lambda

RIs

still cover RDS, ElastiCache, Redshift

utilization

the real trap — waste you already paid for

The quick answer

For most steady compute (EC2, Fargate, Lambda), a Compute Savings Plan is the simplest, most flexible win. For steady RDS, ElastiCache, Redshift, or OpenSearch, Reserved Instances are still the tool, because Savings Plans don't cover those services.

Side-by-side comparison

	Reserved Instances	Savings Plans
Discount	Up to ~72% (can be marginally deeper for a specific type)	Up to ~66% (Compute) / ~72% (EC2 Instance)
Flexibility	Tied to instance family/type (Standard RIs); Convertible RIs allow exchange	Compute SP applies across families, sizes, regions, and Fargate/Lambda
Coverage	EC2, RDS, ElastiCache, Redshift, OpenSearch, and more	EC2, Fargate, Lambda only
Commitment	To a number of instances	To an hourly dollar amount ($/hr)
Terms	1 or 3 years · No / Partial / All upfront	1 or 3 years · No / Partial / All upfront

When Savings Plans win

Your compute mix changes over time (instance families, sizes, regions)
You run Fargate or Lambda alongside EC2
You want to commit once and not manage per-type reservations

When Reserved Instances win

You need to cover RDS, ElastiCache, Redshift, or OpenSearch (Savings Plans don't apply)
You have a stable, specific instance type and want the deepest possible discount

The real trap: utilization, not the choice. A commitment only saves money on usage that actually runs. An under-utilized Savings Plan or Reserved Instance is money you've already paid for and aren't using — pure waste. Before buying more, check the utilization of what you already own; it's the fastest saving of all, with no new purchase.

How to size a commitment safely

Commit to your steady baseline, not your peak. Cover the compute you run 24/7, and leave variable/spiky workloads on on-demand or Spot. No-upfront terms preserve cash flow while still capturing most of the discount; all-upfront squeezes out a bit more if you have the cash. Start conservative — you can always add another Savings Plan later, but you can't easily unwind an over-commitment.

See your commitment coverage & utilization

The AWS Billing Optimizer shows what's uncommitted, what to buy, and which commitments you already own but under-use — read-only, free to start.

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