AWS Commitment Planning · 2026 Guide
AWS Savings Plans vs. Reserved Instances: A Startup-Friendly Guide (2026)
Savings Plans or Reserved Instances? The answer depends on what you're running, how confident you are in your baseline, and how much flexibility you need. Here's the complete breakdown for Series A–C startups.
Side-by-Side Comparison
The key trade-off: Savings Plans are simpler and more flexible; Reserved Instances can go deeper on specific services and offer capacity reservation.
| Attribute | Savings Plans | Reserved Instances | Winner |
|---|---|---|---|
| Discount depth (1-year, no upfront) | Up to 66% (EC2 Instance SP) / ~35% (Compute SP) | Up to 42% (1-year, no upfront) | SP for flexibility, RI for specific committed workloads |
| Flexibility | Compute SP: any instance family, region, OS, tenancy. EC2 Instance SP: locked to family+region. | Convertible RI: can change instance family, size, OS. Standard RI: no changes. | Savings Plans (especially Compute SP) |
| Capacity reservation | No capacity reservation | Standard RIs can reserve capacity in an AZ | Reserved Instances (for capacity needs) |
| Services covered | EC2, Fargate, Lambda (Compute SP). EC2 only (EC2 Instance SP). SageMaker SP also available. | EC2, RDS, ElastiCache, Redshift, OpenSearch, DynamoDB | Reserved Instances (broader service coverage) |
| Applies to Spot Instances | No | No | Neither |
| Management complexity | Simple: one hourly commitment applies automatically | Complex: must match specific attributes (instance type, region, OS, tenancy) | Savings Plans |
Why Savings Plans Win in 2026
Compute Savings Plan advantages
- Applies automatically to any EC2 instance family, size, region, OS, or tenancy
- Also covers Fargate and Lambda (useful for ECS/EKS + serverless architectures)
- One commitment covers your entire compute fleet - no need to track which instances are covered
- Easier to right-size over time: as you change instance types, your commitment still applies
- ~33–35% discount (vs On-Demand) for 1-year, no-upfront - close to Standard RI discount without the lock-in
When RIs still make sense
- RDS: Savings Plans don't cover RDS - you must use Reserved Instances for database discounts
- ElastiCache, Redshift, OpenSearch: same - RI is the only commitment option
- Capacity reservation: if you need guaranteed capacity in a specific AZ (e.g., ML workloads), Standard RIs are the only option
- EC2 Instance Savings Plans: if you know exactly which instance family you'll use, these go deeper (up to 66% discount)
The Startup Trap: Over-Committing Before Rightsizing
The most expensive commitment mistake is buying Savings Plans or RIs before rightsizing. If you commit to $5,000/month in Savings Plans and then downsize your EC2 fleet by 40%, you're now paying for capacity you don't use - and you're locked in for 1–3 years.
The correct sequence: Rightsize → then commit to the new lower baseline.
How to calculate your commitment baseline
- 1. Complete your rightsizing changes first.
- 2. Wait 2–4 weeks for the cost data to reflect the new baseline.
- 3. In Cost Explorer → Savings Plans → Recommendations, use the 30-day trailing lookback.
- 4. Commit to 70–80% of the recommended amount (leave buffer for scale-down months).
- 5. Reassess every 3 months. Buy additional Savings Plans as your baseline grows.