Quick Overview
| Attribute | Reserved Instances | Savings Plans |
|---|---|---|
| Max discount | 72% (Standard RI, 3yr, upfront) | 66% (Compute SP, 3yr) |
| Flexibility | Low (tied to instance family/region) | High (any instance type/region) |
| What you commit to | Specific instance type | $/hour spend level |
| Covers Lambda? | No | Yes (Compute SP) |
| Covers Fargate? | No | Yes (Compute SP) |
| Sellable on marketplace? | Yes (Standard only) | No |
| Management complexity | High | Low |
Reserved Instances: When They Win
Standard RIs offer the highest absolute discount — up to 72% for 3-year, all-upfront commitments. They're best for workloads that are extremely stable in instance type, size, and region. Think: your primary database servers, a fixed-size web tier that's been the same for 2+ years.
Standard vs Convertible RIs: Standard RIs save more but can't be exchanged. Convertible RIs allow you to change instance family, OS, or tenancy — the tradeoff is a lower discount (54% max vs 72%). For most teams, Convertible RIs hit the right balance.
Savings Plans: The Modern Choice
Savings Plans were introduced in 2019 and are now AWS's preferred commitment model. You commit to spending a minimum $/hour over 1 or 3 years. AWS automatically applies the discount to any eligible usage — regardless of instance type, region, or OS. This flexibility makes them far easier to manage as your infrastructure evolves.
Compute Savings Plans cover EC2, Lambda, and Fargate — the broadest coverage.
EC2 Instance Savings Plans are locked to an instance family in a region, but offer slightly higher discounts (similar to Convertible RIs).
Real-World Savings Comparison
For a $50,000/month EC2 spend on stable m5.xlarge instances in us-east-1:
| Option | 1-Year No Upfront | 1-Year Full Upfront | 3-Year Full Upfront |
|---|---|---|---|
| Standard RI (m5.xlarge) | 40% | 43% | 62% |
| Convertible RI (m5.xlarge) | 31% | 35% | 54% |
| Compute Savings Plan | 35% | — | 66% |
| EC2 Instance Savings Plan | 37% | — | — |
Which Should You Choose?
Choose Compute Savings Plans if: Your instance types change regularly, you use Lambda or Fargate, you want minimal management overhead, or you're not confident your baseline won't shift.
Choose Standard RIs if: Your database or core instances have been identical for 2+ years, you want maximum discount, and you're willing to sell unused RIs on the marketplace if needed.
Recommended hybrid approach: Cover your stable baseline (databases, always-on services) with Standard RIs. Cover variable compute with Compute Savings Plans. Leave 15–20% of expected usage as on-demand buffer.