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/Saving Plan Showing as underused, but still being charged on-demand usage./

Saving Plan Showing as underused, but still being charged on-demand usage.

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Hi there!

On Dec 1st I submitted a purchase for a savings plan which should cover m5 family ec2 instance usage on us-east-1 region. I made the calculations to cover roughly what I was planning to use, but when looking at the billing details, it shows it only covered around %40 of the actual usage; but again, when looking at the saving plans usage, it shows only %54 of it was used. I couldn't figure out why all the usage wasn't being applied agaisnt the savings plan. The instance usage I intended to cover with this plan was a m5.2xlarge running Windows with SQL Enterprise. (The only m5 instance I'm actively using in this region)

Unfortunatelly I can't post screenshots, but my m5 coverage report on us-east-1 region shows 44% coverage, but on the other hand my Saving plan utilization report shows only 54% usage.

Thanks!!

  • What rate did you purchase? Which payment option? No Upfront, Partial, All? Was it compute or ec2 instance savings plan?

1 Answers
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Accepted Answer

The most likely reason is that your instance that is supposed to match attributes of your Savings Plan is not running 24/7. And also, during some hours you may be running more instances than you have Savings Plans.

Billing works hourly. Let's say you purchased Savings Plans for 1yr term. You are committing to pay for the full term and the full price for that Savings Plan. If you are running matching instances, and your SP applies to them, then you will not get on-demand charges for those instances, but will essentially only pay for SP.

Because billing works hourly, generally you need to check your hourly utilization. Let's assume you purchsed SP based on the assumption that you would run 2 instances 24/7:

  • Let's say you purchase SP based on the calculation of the total number of hours you run your M5 instances in a month.
  • But let's say you always run 3 instances between 12:00 and 00:00. And then you run only 1 instance between 00:00 and 12:00. On average you run 2 instances throughout the whole day.
  • In this example, between 12:00 and 00:00 you will get 100% utilization of your SP, but you will also get extra on-demand charges for an extra running instance. But between 00:00 and 12:00 you will only have 50% utilization of your SP, and no on-demand charges.

I hope this helps.

EXPERT
answered 4 months ago
  • Thanks Nataliya, I reviewed your example, and in fact I wasn't aware that hourly usage was not added up and could be distributed across different days if instances where not running 24/7. So basically, I made a mistake on the calculations based on the concept not being clear for me. I'll try to ask AWS support for a cancelation on the savings plan, I know there are some occasions where if the contract is purchased by mistake there could be a one-time courtesy cancellation; so, wish me luck!!:)

    Regards!

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