01
Fix the time boundary before multiplying
Tungsto monthly renewals represent 30-day service periods. Thirty-six such periods equal 1,080 days. That is not the same as 36 calendar months, which span 1,095 days or 1,096 days when the selected interval includes a leap day. Choose one model and put the exact start date, end date, time zone and billable hours or seconds at the top of both worksheets.
If the analysis uses 1,080 days, label the output 36 thirty-day billing periods rather than silently calling it three calendar years. If procurement requires 36 calendar months, price the dedicated renewals and cloud runtime across those exact dates. This prevents a small time mismatch from being presented as a platform saving.
02
Define an equivalent service envelope
Describe the workload before selecting products: operating system, sustained and peak CPU, resident memory, local and durable storage, I/O pattern, public addressing, monthly transfer, backup retention, recovery targets and regions. A single dedicated host is not automatically comparable to a cloud design spread across zones, just as one cloud instance is not comparable to a bare-metal host with all cores continuously available.
Create two architectures that satisfy the same stated outcome. If failover is required, include standby compute, replicated storage, load balancing and operator procedures on both sides. If elasticity is a requirement, model the actual schedule and peak shape instead of charging a dedicated server at full utilization and an undersized cloud instance only during quiet hours.
03
Build a complete, sourced cost ledger
For dedicated rental, include the selected term price, any additional addresses or services, external backups, software licences and administration. For cloud, include compute purchase model, block or object storage, provisioned performance, snapshots, backup retrieval, data transfer, public addresses, load balancers, monitoring, support and the same licences and staff work. Keep tax and currency conversion rules consistent.
Use a dated provider calculator export instead of a remembered price. AWS documents separate estimate inputs for instances, EBS, monitoring, transfer, addresses and additional costs; other providers have their own rules. On-demand compute may be billed by the second while storage and transfer use different dimensions, so one monthly placeholder cannot represent the whole architecture.
Build a complete, sourced cost ledger| Ledger group | Dedicated model | Cloud model |
|---|
| Compute | Term renewals for required hosts | Runtime by instance and purchase model |
|---|
| Data | Local layout plus external backup | Volumes, snapshots, object storage and retrieval |
|---|
| Network | Included port plus stated extras | Ingress, egress, addresses and balancing rules |
|---|
| Operations | Monitoring, patching and recovery work | Platform operations plus managed-service premiums |
|---|
04
Run sensitivity cases instead of one forecast
Keep every uncertain input visible. Recalculate for lower and higher utilization, transfer, storage growth, backup retention and operator hours. Add a commitment-expiry case for cloud discounts and a replacement or migration case for the dedicated design. Do not invent competitor prices or performance; enter current quoted values and record their retrieval date.
A useful break-even statement is conditional: at the selected runtime, transfer and staffing assumptions, one design costs less over the fixed horizon. It is not a universal claim about cloud or bare metal.
05
Produce an auditable decision
The expected result is a bill of materials for each architecture, a common day boundary, source links, three sensitivity cases and a list of excluded benefits or risks. Include migration effort, lock-in, scaling speed and hardware isolation as decision factors even when they are not reduced to dollars. Review actual invoices and utilization periodically; the model is a decision record, not a promise that future prices or workload demand will remain fixed.
Direct answers
Questions about this guide
Why does 36 times a monthly price not always equal three calendar years?
Because Tungsto uses 30-day monthly service periods. Thirty-six periods are 1,080 days, while 36 calendar months are normally 1,095 or 1,096 days depending on the dates. Use the same explicit horizon on both sides.
Should staff time be excluded because both platforms need administrators?
No. Include only work attributable to each comparable design, using a stated rate or hours assumption. Managed services may reduce some tasks and introduce others; do not assign an unsupported universal saving.