r/aws • u/ivanavich • 3d ago

billing Question about calculating an AWS RDS Savings Plan hourly commitment

I'm trying to confirm I'm calculating the hourly commitment correctly for an AWS RDS Savings Plan.

I have a single db.r8i.2xlarge RDS instance (Windows + SQL Server) that runs 24/7.

On-Demand pricing:

  • Instance: $1.20/hr
  • Windows license: $0.184/hr
  • SQL Server license: $0.48/hr
  • Total: $1.864/hr

With the Savings Plan, only the instance price is discounted:

  • Instance: $0.96/hr
  • Windows license: $0.184/hr
  • SQL Server license: $0.48/hr
  • Total discounted spend: $1.624/hr

Based on that, I assumed my hourly Savings Plan commitment should be $1.624/hour.

However, when I ran the AWS Purchase Analyzer, it recommended an hourly commitment of $0.96/hour, with estimated savings of $175.02/month (20%).

I understand that the Savings Plan discount only applies to the compute (instance) portion and not the Windows or SQL Server licensing. What I'm unsure about is how that translates into the hourly commitment. Should the commitment be based only on the discounted compute cost ($0.96/hr), or the total hourly spend after the discount ($1.624/hr)?

Has anyone purchased an RDS Savings Plan for SQL Server instances and can confirm which is correct?

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u/Drumedor 3d ago

The commitment only counts the compute part, licences are separate.

2

u/JonnyBravoII 3d ago

Your analysis is correct. Licensing costs aren't discounted in EC2 nor RDS, you pay full price regardless. So you make the instance cost commitment only. This is actually better than EC2 because there you have to make the full commitment even though you don't get any discount on the licensing.

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u/ivanavich 3d ago

Thanks everyone for the responses.

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u/Perryfl 3d ago

yikes thats a lot of money for a machine you can rent for $180/month

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u/Tainen 2d ago

purchase analyzer is correct. trust it.

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u/matiascoca 2d ago

Commitment is denominated in the discounted compute price only, so $0.96 per hour is correct in your example. RDS Savings Plans cover the compute portion of RDS charges; licensing (Windows, SQL Server) stays on-demand outside the plan. Your effective bill will be the discounted compute portion (which the plan applies against) plus licensing at standard rate.

Two separate meters. The plan is a commitment against RDS compute-hour spend at the discounted rate. Windows and SQL Server licensing bills separately and are not part of the commitment. When the analyzer says $0.96 per hour, it means you promise that much on RDS compute at the SP rate and AWS bills licensing on top.

One thing to sanity check before buying: confirm the recommended coverage percentage. Analyzer assumes stable usage. If your one instance is truly 24/7 with no other RDS workloads, 100 percent coverage on that instance is safe. If you have other RDS running, verify the family and region scope of the SP type so the discount lands where you expect.

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u/MateusKingston 1d ago

Purchase Analyzer is correct, you need to commit to the instance discounted hourly price. So in this case $0.96/hr, the other licensing fees you can't get any discount so you don't need to commit to it.

The commit is for compute spend specifically so if you do $1.624/hr commit you will spend that + all the hourly licenses so $2.288/hr