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On-Premises Cost Modeling and TCO Analysis

Scope

This file covers on-premises cost modeling and total cost of ownership (TCO) analysis including hardware depreciation, power and cooling, software licensing, staffing overhead, and cloud comparison frameworks. For cloud-native cost optimization, see general/cost.md.

Checklist

  • [Critical] Is the hardware depreciation schedule defined (3-year for performance-sensitive/fast-evolving hardware, 5-year for general compute), and is the monthly equivalent cost calculated for CapEx-to-OpEx comparison (monthly = purchase price / depreciation months)?
  • [Critical] Are all software licensing costs captured including hypervisor (per-socket or per-core), management tools (per-node), backup (per-VM or per-TB), monitoring, and OS licenses -- with support/maintenance renewal costs for years 2-5?
  • [Critical] Is power and cooling cost calculated per node using measured wattage (300-800W typical per 2U server), PUE multiplier (1.4-1.8 for enterprise DC), and local electricity rate ($/kWh), projected across the depreciation period?
  • [Recommended] Are data center space costs included -- per-rack-unit monthly rates for colocation ($50-$200/U/mo depending on market), or allocated building/facilities cost for owned datacenters?
  • [Recommended] Are network circuit costs included -- WAN/MPLS ($500-$5,000/mo per site), internet ($100-$2,000/mo per circuit), cross-connects ($100-$500/mo per cross-connect), and bandwidth overage charges?
  • [Recommended] Is staffing overhead allocated -- what fraction of FTE time is dedicated to infrastructure management (server, storage, network, backup), and is this costed at fully-burdened rate ($120K-$200K/yr per FTE in US)?
  • [Recommended] Is the TCO framework capturing all cost categories: CapEx (hardware, initial licensing), OpEx (power, cooling, space, circuits, support renewals), and staffing (allocated FTE time)?
  • [Recommended] Is a cloud comparison analysis prepared using equivalent cloud configurations (instance types, storage tiers, networking) at 1-year, 3-year, and 5-year horizons including reserved/committed pricing?
  • [Optional] Is hardware residual value estimated at end of depreciation period (typically 5-15% of original cost for 3-year-old servers, near zero for 5-year-old)?
  • [Optional] Is opportunity cost considered -- what projects or innovations are deferred because team is spending time on infrastructure maintenance versus application development?
  • [Optional] Are refresh cycle costs modeled -- when hardware reaches end-of-depreciation, what is the cost of the replacement cycle including migration labor, parallel running costs, and disposal/recycling?
  • [Recommended] Are growth projections included -- is the cost model accounting for 20-30% annual capacity growth (industry average) and the "lumpiness" of on-prem scaling (must buy full nodes/racks vs. cloud's per-VM granularity)?
  • [Optional] Is a financial model built that shows monthly burn rate to enable direct comparison with cloud's monthly billing model?

Why This Matters

On-prem vs. cloud cost comparisons are the most frequently debated and most frequently wrong analysis in enterprise IT. On-prem advocates often undercount costs by including only hardware purchase price and ignoring power, cooling, space, staffing, and opportunity cost -- this makes on-prem appear 50-70% cheaper than cloud when the real difference may be 10-20% or even favoring cloud. Cloud advocates often compare list-price on-demand instances against fully depreciated on-prem hardware -- ignoring reserved instances, committed use discounts (40-60% off on-demand), and the fact that cloud costs scale linearly with consumption while on-prem costs are largely fixed after purchase. A rigorous TCO analysis is an ADR-worthy decision that should be revisited every 2-3 years as both cloud pricing and on-prem technology evolve. The analysis must also consider non-financial factors: speed of provisioning (minutes in cloud vs. weeks/months for on-prem procurement), data sovereignty requirements, and team skill sets.

Common Decisions (ADR Triggers)

  • 3-year vs 5-year depreciation -- 3-year aligns with warranty periods and technology refresh cycles (newer hardware is ~20-30% more power efficient), creates higher monthly costs but avoids running out-of-warranty hardware. 5-year reduces monthly cost by ~40% but risks running hardware past peak reliability (failure rates increase significantly in years 4-5). Most enterprises use 3-year for compute, 5-year for network switches and power infrastructure.
  • CapEx vs OpEx (purchase vs lease/subscription) -- Purchasing hardware is CapEx (balance sheet asset, depreciated over time, favorable for companies with available capital and tax depreciation benefits). Leasing or hardware-as-a-service (Dell APEX, HPE GreenLake, Nutanix NX-as-a-Service) converts to OpEx (monthly expense, no asset on books, easier budget approval in OpEx-oriented organizations). Subscription models typically cost 15-25% more over the hardware lifetime but provide flexibility and refresh guarantees.
  • Colocation vs owned datacenter -- Colocation ($500-$2,500/mo per rack including power and cooling) provides professional DC facilities without building/managing them, scales from 1 rack to cages/suites, and allows geographic distribution. Owned DC provides full control and lower per-rack cost at scale (>50 racks) but requires significant CapEx, facilities team, and 18-24 month build timeline. Most enterprises below Fortune 500 use colocation.
  • Cloud repatriation threshold -- Workloads that are stable (predictable resource consumption), long-running (24/7 not burst), and do not need cloud-native services (managed databases, serverless, AI/ML APIs) are candidates for on-prem at the 3-5 year horizon. The break-even point is typically 60-70% sustained utilization -- below that, cloud reserved instances are often cheaper. Each workload should be evaluated individually.
  • Software licensing: per-node vs per-core vs subscription -- Per-node licensing (e.g., Nutanix, some backup products) favors dense nodes with many cores. Per-core licensing (e.g., SQL Server, Oracle, Red Hat) penalizes dense nodes -- consider deploying fewer cores per node or using Standard vs Enterprise editions. Subscription licensing (annual) provides current version access and support but creates recurring OpEx; perpetual licensing (one-time) is cheaper long-term but requires separate support contracts and may fall behind on versions.

Cost Calculation Framework

Per-Node Monthly Cost

Hardware (monthly)    = Purchase Price / (Depreciation Years x 12)
                      Example: $25,000 / (5 x 12) = $416.67/mo

Power (monthly)       = Node Watts x PUE x Hours/Month x $/kWh
                      Example: 500W x 1.5 x 730h x $0.10 = $54.75/mo

Cooling               = Included in PUE multiplier (above)

Space (colo, monthly) = Rack Units x $/RU/mo
                      Example: 2U x $75/U = $150/mo
                      (Or: $1,500/mo per rack / nodes per rack)
                      Example: $1,500 / 10 nodes = $150/mo

Software (monthly)    = Annual License & Support / 12
                      Example: $12,000/yr / 12 = $1,000/mo per node

Network (allocated)   = Circuit Costs / Nodes Served
                      Example: $3,000/mo circuits / 40 nodes = $75/mo

Staffing (allocated)  = (FTEs x Fully-Burdened Salary) / Nodes Managed
                      Example: (2 FTE x $180,000/yr) / 40 nodes / 12 = $750/mo

─────────────────────────────────────────────────────
TOTAL PER-NODE/MO   = $416.67 + $54.75 + $150 + $1,000 + $75 + $750
                    = $2,446.42/mo per node

TCO Summary Template

Cost Category Year 1 Year 2 Year 3 Year 4 Year 5 Total
Hardware (CapEx) $X $0 $0 $0 $0 $X
Software licenses $X $X $X $X $X $5X
Support/maintenance $X $X $X $X $X $5X
Power & cooling $X $X $X $X $X $5X
DC space (colo) $X $X $X $X $X $5X
Network circuits $X $X $X $X $X $5X
Staffing (allocated) $X $X $X $X $X $5X
Total $TCO
Residual value -$R -$R
Net TCO $TCO - $R

Cloud Comparison Template

Metric On-Prem (5yr) Cloud On-Demand (5yr) Cloud Reserved (5yr)
Compute $X $Y (list price) $Z (1yr RI/CUD)
Storage $X $Y $Z
Networking $X $Y (egress!) $Z
Licensing $X Included or BYOL Included or BYOL
Staffing $X $X (reduced ~30%) $X (reduced ~30%)
Total $A $B $C
Break-even utilization N/A >X% sustained >Y% sustained

Key cloud cost traps: - Data egress charges ($0.08-$0.12/GB) can dominate costs for data-heavy workloads - Cloud storage (EBS, managed disks) is 5-10x more expensive per TB than local NVMe - Cloud networking (load balancers, NAT gateways, VPN connections) adds $200-$1,000+/mo in hidden costs - Licensing in cloud: SQL Server on AWS/Azure can be 2-4x more expensive than on-prem with Software Assurance

Common Software Licensing Models

Vendor/Product Model Approximate Cost Notes
Nutanix (NCI) Per-node, subscription $5,000-$15,000/node/yr Starter/Pro/Ultimate tiers
VMware vSphere Per-core, subscription $200-$500/core/yr Changed from per-socket to per-core in 2024
Red Hat Enterprise Linux Per-subscription (2-socket entitlement for physical servers, unlimited VMs per subscription) Varies by support tier (Standard $799/yr, Premium $1,299/yr) Self-support also available at lower cost
Microsoft Windows Server Per-core (min 16/server) $800-$6,000/server Standard (2 VMs) vs Datacenter (unlimited VMs)
SQL Server Per-core (min 4) $3,700-$15,000/core Standard vs Enterprise, SA adds ~25%/yr
Veeam Backup Per-VM or per-workload $50-$200/VM/yr Universal License model
Commvault Per-TB front-end Varies widely Complex licensing, get quote

Reference Architectures

  • Gartner TCO Model: Gartner publishes comprehensive TCO methodologies for infrastructure comparison -- available to Gartner subscribers, frequently cited in enterprise decision-making
  • AWS TCO Calculator: calculator.aws -- useful for generating cloud-side costs for comparison, but note it is designed to favor cloud (does not include all on-prem cost reductions)
  • Nutanix TCO Calculator: Available through Nutanix sales -- models HCI-specific TCO against traditional three-tier and cloud, includes power/cooling/space
  • Uptime Institute PUE: uptimeinstitute.com -- industry benchmarks for Power Usage Effectiveness; global average is ~1.58, best-in-class hyperscalers achieve 1.1-1.2
  • IDC CloudTrack: IDC research on cloud vs on-prem cost comparison across enterprise segments -- useful for benchmarking your analysis against industry data
  • FinOps Foundation: finops.org -- practices for cloud financial management; applicable to on-prem cost discipline as well

See Also