Comparison
Two commitments, both sold as reservations — they aren't the same bet.
A Reserved Instance commits to a specific instance class, in a region, for a service. A Savings Plan commits to an hourly dollar amount of compute spend, and lets the discount follow whatever usage qualifies. Here's an honest head-to-head, when each one fits, and the failure mode they share.
First, the two commitments
Same idea — pay now, save later — two different things to commit to.
A Reserved Instance is a commitment to a specific instance class in a specific region, for a service — RDS, ElastiCache, or EC2 — in exchange for a lower rate on any usage that matches it exactly. A Savings Plan is a commitment to spend a fixed dollar amount per hour on compute — EC2, Fargate, or Lambda — and AWS applies the discount automatically to whatever qualifying usage shows up, regardless of instance family, size, region, or OS. One reserves a thing; the other reserves a number.
In practice that means an RI on a db.r6g.xlarge only discounts a db.r6g.xlarge — resize it and the reservation has nothing left to cover. A Savings Plan sized to the same hourly spend keeps discounting even if that workload moves to a different instance family or off EC2 entirely, as long as the dollar commitment is still being spent somewhere eligible.
Head-to-head
Neither one wins outright — they cover different ground.
All figures below are AWS's own published ceilings, not a quote — your actual rate depends on instance class, region, term, and payment option.
| Dimension | Reserved Instance | Savings Plan |
|---|---|---|
| What it locks in | ✓a specific instance family, region, and service | ✓a $/hour of compute spend, service-agnostic |
| Flexes across instance family, size, region, or OS | ~EC2 Convertible only — Standard EC2 and all RDS/ElastiCache RIs are fixed to what you bought | ✓discount follows usage wherever it lands, automatically |
| Covers Amazon RDS and ElastiCache | ✓ | ✗compute only — RDS and ElastiCache aren't eligible |
| Covers EC2, Fargate, and Lambda compute | ~EC2 only | ✓Compute Savings Plans span all three |
| Published max discount vs on-demand | ✓up to 72% EC2 · 69% RDS · 55% ElastiCache | ✓up to 72% (EC2 Instance SP) · 66% (Compute SP) |
| Resellable on the AWS Marketplace | ✓EC2 Standard RIs only, unused term | ✗ |
| 1-year and 3-year terms, No/Partial/All Upfront payment | ✓ | ✓ |
| Auto-renews at term end | ✗reverts silently to on-demand | ✗reverts silently to on-demand |
Reserved Instance
- ✓What it locks in — a specific instance family, region, and service
- ~Flexes across instance family, size, region, or OS — EC2 Convertible only — Standard EC2 and all RDS/ElastiCache RIs are fixed to what you bought
- ✓Covers Amazon RDS and ElastiCache
- ~Covers EC2, Fargate, and Lambda compute — EC2 only
- ✓Published max discount vs on-demand — up to 72% EC2 · 69% RDS · 55% ElastiCache
- ✓Resellable on the AWS Marketplace — EC2 Standard RIs only, unused term
- ✓1-year and 3-year terms, No/Partial/All Upfront payment
- ✗Auto-renews at term end — reverts silently to on-demand
Savings Plan
- ✓What it locks in — a $/hour of compute spend, service-agnostic
- ✓Flexes across instance family, size, region, or OS — discount follows usage wherever it lands, automatically
- ✗Covers Amazon RDS and ElastiCache — compute only — RDS and ElastiCache aren't eligible
- ✓Covers EC2, Fargate, and Lambda compute — Compute Savings Plans span all three
- ✓Published max discount vs on-demand — up to 72% (EC2 Instance SP) · 66% (Compute SP)
- ✗Resellable on the AWS Marketplace
- ✓1-year and 3-year terms, No/Partial/All Upfront payment
- ✗Auto-renews at term end — reverts silently to on-demand
When to choose which
The choice follows the shape of the usage, not the size of the bill.
Most fleets with any real history don't pick one — they use RIs where usage is nailed down and a Savings Plan where it isn't, and revisit the split as the fleet's shape changes.
How this scales with you
The RI-vs-Savings-Plan call matters at 1 reservation and at 1,000.
Usually just RIs — a small, steady RDS or ElastiCache footprint doesn't need a spend-based commitment. Simplicity and marketplace resale matter more than flexibility at this size.
The mix starts to matter: RIs for the steady RDS/ElastiCache floor, a Savings Plan layered on top of EC2 usage that's beginning to shift between instance families or into containers.
Most real fleets at this scale run both, deliberately — RIs for anything with a stable footprint and resale value, Savings Plans for compute that moves. The choice is made once, per workload, not re-litigated purchase by purchase.
The tooling should scale the same way the decision does: one flat price whether it's covering a handful of reservations or thousands — see pricing — never a cut of what you save.
The shared failure mode
Neither one renews itself.
Whichever you buy, the term still ends on a fixed date, and AWS doesn't prompt anyone when it does. A lapsed Reserved Instance and a lapsed Savings Plan fail identically: the running usage doesn't change at all, only the price does — it reverts to the standard on-demand rate immediately and silently, and stays there until somebody notices and buys again. See the renewal playbook for the full mechanics of the cliff, or run your own numbers on the savings calculator — a small, fixed cost to watch for the lapse against a large, avoidable loss if nobody does, whether it's one commitment or a thousand.
Where Reserver fits
RIs today. Savings Plans on the roadmap.
Reserver connects to your AWS accounts read-only and, today, matches Reserved Instances to what's actually running across RDS, ElastiCache, and EC2 — coverage maps, purchase recommendations with the math shown, one-click buying, and renewal autopilot. Savings Plans are on our roadmap, not shipping yet — if your fleet already blends both, Reserver's coverage view is only the RI half of the picture for now, honestly. See features, how it works, and the security model behind the read-only connection, or read the savings playbook and the coverage playbook for the RI side of the math.
Can I use Reserved Instances and Savings Plans together?
Yes — they're not mutually exclusive, and most fleets of any real size use both. AWS applies Reserved Instance discounts first to anything they match, then applies any Savings Plan commitment to what's left. A common split is RIs on steady RDS/ElastiCache/EC2 usage and a Savings Plan layered over compute that shifts.
Which one saves more money?
Neither wins outright — it depends on how stable the usage is. A Reserved Instance on usage that never changes can match a Savings Plan's discount depth while adding marketplace resale as a safety net. A Savings Plan on usage that resizes or moves keeps discounting through changes an RI would just stop covering. The right answer is usage-shape-dependent, not a fixed ranking.
Do Savings Plans cover RDS or ElastiCache?
No. Savings Plans apply to compute usage only — EC2, Fargate, and Lambda. RDS and ElastiCache reservations only exist as Reserved Instances; there's no spend-based commitment option for either service today.
Does a Savings Plan auto-renew like a subscription?
No — this is the trap both share. A Savings Plan is a fixed-term commitment exactly like a Reserved Instance: when the term ends, the hourly spend commitment simply stops, and every dollar of usage it was discounting reverts to the standard on-demand rate immediately and silently.
Stop overpaying for a steady fleet.
Reserver is in early access. Join the list and we'll onboard you as capacity opens up — first recommendation within minutes of connecting.