Should you buy Reserved Instances or Savings Plans? Both provide significant discounts (30-60%) for committed cloud usage, but they work differently and suit different scenarios. This guide helps you choose the right commitment type for your workloads.
Key Takeaways
- Savings Plans offer more flexibility: They apply across instance families, regions, and even between EC2 and Fargate.
- Reserved Instances still win for specific services: RDS, ElastiCache, and Redshift only support Reserved Instances, not Savings Plans.
- Start with Compute Savings Plans: Maximum flexibility for your first commitments. Layer specific plans once you have confidence in stability.
- 1-year commitments first: Start with 1-year terms to reduce risk. Move to 3-year terms for stable workloads where you are confident in longevity.
Comparison Table
| Feature | Compute Savings Plans | EC2 Instance Savings Plans | Reserved Instances |
|---|
| Discount | 20-40% (1yr) / 30-55% (3yr) | 30-50% (1yr) / 40-60% (3yr) | 30-45% (1yr) / 40-72% (3yr) |
| Instance family flex | Yes — any family, any size | Yes — any size within family | Limited (Standard) or Yes (Convertible) |
| Region flexibility | Yes — any region | No — locked to region | No — locked to AZ or region |
| Service flexibility | EC2, Fargate, Lambda | EC2 only | Specific service (EC2, RDS, etc.) |
| OS flexibility | Yes | No — locked to OS | No — locked to OS |
| Payment options | All Upfront, Partial, No Upfront | Same | Same |
| Marketplace resale | No | No | Yes (Standard RIs) |
Decision Framework
When to use Compute Savings Plans
- You are making your first commitment purchase
- Your workloads may change instance family or region
- You use Fargate or Lambda alongside EC2
- You want maximum flexibility with good discounts
- You are not sure about long-term infrastructure stability
When to use EC2 Instance Savings Plans
- You are confident about instance family and region for specific workloads
- You want deeper discounts than Compute Savings Plans
- Your workloads are stable and unlikely to move
When to use Reserved Instances
- RDS, ElastiCache, Redshift, OpenSearch — these only support RIs, not Savings Plans
- You want to resell unused commitments on the RI Marketplace
- You need the deepest possible discounts for very stable workloads
Commitment Strategy
Layer 1: Compute Savings Plans (cover 60-70% of baseline)
Start by calculating your minimum steady-state compute spend — the amount you are confident spending every hour, every day. Purchase Compute Savings Plans to cover 60-70% of this baseline. This provides good discounts with maximum flexibility.
Layer 2: EC2 Instance Savings Plans (cover 15-20% more)
For workloads that you are confident will remain in the same instance family and region, add EC2 Instance Savings Plans for deeper discounts. Typically covers database servers, core application servers, and other stable infrastructure.
Layer 3: Reserved Instances (cover specific services)
Purchase RIs for RDS, ElastiCache, and other services that only support RIs. Match RI specifications exactly to your running resources.
Layer 4: On-Demand and Spot (remaining variable usage)
Keep 10-20% of compute on-demand for variable workloads. Use Spot instances for fault-tolerant workloads (batch processing, CI/CD, dev environments) to save 60-90% on variable compute.
How Opsio Manages Commitments
- Commitment analysis: We analyze your usage patterns to recommend the optimal commitment portfolio.
- Purchase management: We execute commitment purchases on your behalf with proper sizing and timing.
- Quarterly rebalancing: We review commitment utilization and adjust the portfolio as workloads change.
- Expiration management: We track commitment expirations and recommend renewals or changes based on current usage.
Frequently Asked Questions
What if my workloads change after I commit?
Compute Savings Plans apply to any instance type or region — if you change workloads, the discount still applies. EC2 Savings Plans and Standard RIs are less flexible. Start with Compute Savings Plans if you are uncertain about stability.
Should I pay all upfront for maximum discount?
All-upfront provides the deepest discount (additional 5-10%) but requires significant capital. No-upfront requires no initial investment and still provides 20-40% savings. Partial upfront is the common middle ground. Choose based on your capital availability and cash flow preferences.
How do I avoid over-committing?
Cover only 60-70% of your minimum steady-state usage with your first round of commitments. Monitor utilization for 3 months, then add commitments for the stable portion of remaining usage. Never commit 100% — you need headroom for usage changes and optimization.
Editorial standards: This article was written by a certified practitioner and peer-reviewed by our engineering team. We update content quarterly to ensure technical accuracy. Opsio maintains editorial independence — we recommend solutions based on technical merit, not commercial relationships.
