Direct answer: at the Azure Retail Prices API on 9 November 2026 (eastus, Linux, USD, excluding tax/discounts), D4ps_v5 (4 vCPU/16GB Arm) costs $0.154/hour on-demand (about $112.42/month), $0.032556/hour on Spot (about $23.77/month, 78.9% off), $796/year for a 1-year reservation (about $0.090868/hour, $66.33/month, 41.0% off) and $1,538/3 years for a 3-year reservation (about $0.058524/hour, $42.72/month, 62.0% off). D4s_v5 (4 vCPU/16GB x86) costs $0.192/hour on-demand (about $140.16/month), $0.040531/hour on Spot (about $29.59/month, 78.9% off), $1,038/year for 1-year (about $0.118493/hour, $86.50/month, 38.3% off) and $1,993/3 years for 3-year (about $0.075837/hour, $55.36/month, 60.5% off). Decision rule: on pure compute, Spot is usually about 45% cheaper than a 3-year reservation, but it has no SLA, a 30-second notice and can be evicted; reservations only win when “eviction frequency × recovery time” exceeds about 0.44–0.47 (vs 3-year) or 0.64–0.66 (vs 1-year).
This guide is for Azure platform, SRE, batch/HPC, CI/CD and FinOps teams. It explains Azure Spot, on-demand and 1/3-year reservation billing and coverage, provides D4ps_v5/D4s_v5 TCO, an eviction/recovery break-even model, hidden costs and a 90-day checklist. Prices come from the Azure Retail Prices API (eastus, 9 November 2026); Spot and reservation behavior comes from Microsoft Learn documentation. Official price facts, editorial calculations and exclusions are kept separate. This is not procurement advice.
(1) Separate “saving compute” from “buying stability”: Spot saves compute cost but offers no SLA and can be evicted with 30 seconds' notice; reservations buy a stable price but storage/network/licenses are still extra. (2) Spot does not always win: do a break-even on “eviction frequency × recovery time”; slower recovery and more frequent evictions favor reservations. (3) Reservations are not all-inclusive: they cover VM compute only—not Windows/software/network/storage; 3-year discounts are deeper but lock you in longer, so buy the stable baseline first.
Billing models: Spot, on-demand and 1/3-year reservations
Azure Spot bills at the current Spot price, with an optional max price; when the price exceeds the max or Azure needs capacity, the VM is evicted with up to 30 seconds' notice via Scheduled Events (best effort) and no SLA. The eviction policy is Deallocate (default: VM stops, disks continue billing) or Delete (VM and disks deleted). On-demand bills the standard VM price with an SLA. Reservations are 1- or 3-year compute discounts covering VM compute only—not Windows/software/network/storage; same-type reservations can be exchanged and refunds have limits.
| Model | Billing/discount | SLA/interruption | Coverage |
|---|---|---|---|
| Spot | Current Spot price; up to 90% off | No SLA; 30s notice; capacity/price eviction | VM compute; disks/network extra |
| On-demand | Standard VM price | SLA; available when capacity allows | VM compute; disks/network extra |
| 1-year reservation | About 38–41% off (examples) | Stable price; no capacity guarantee | VM compute only |
| 3-year reservation | About 60–62% off (examples) | Stable price; no capacity guarantee | VM compute only |
Sources: Azure Spot product page/docs, Azure reservations docs (9 November 2026). Discounts are editorial calculations for the example sizes; the pricing page/bill is authoritative.
Unit prices and discounts: D4ps_v5 and D4s_v5
D4ps_v5 (Arm, 4 vCPU/16GB): on-demand $0.154/hour; Spot $0.032556 (78.9% off); 1-year $796/year, 3-year $1,538/3 years. D4s_v5 (x86, 4 vCPU/16GB, Linux): on-demand $0.192/hour; Spot $0.040531 (78.9% off); 1-year $1,038/year, 3-year $1,993/3 years. Effective hourly: D4ps 1-year $0.090868, 3-year $0.058524; D4s 1-year $0.118493, 3-year $0.075837. Spot is about 44–47% below 3-year and 64–66% below 1-year.
| Size/model | Price (USD) | Monthly/note |
|---|---|---|
| D4ps_v5 on-demand | $0.154/hour | $112.42/month |
| D4ps_v5 Spot | $0.032556/hour | $23.77/month; 78.9% off |
| D4ps_v5 1-year | $796/year ($0.090868/h) | $66.33/month; 41.0% off |
| D4ps_v5 3-year | $1,538/3 years ($0.058524/h) | $42.72/month; 62.0% off |
| D4s_v5 on-demand | $0.192/hour | $140.16/month |
| D4s_v5 Spot | $0.040531/hour | $29.59/month; 78.9% off |
| D4s_v5 1-year | $1,038/year ($0.118493/h) | $86.50/month; 38.3% off |
| D4s_v5 3-year | $1,993/3 years ($0.075837/h) | $55.36/month; 60.5% off |
Source: Azure Retail Prices API (eastus, Linux, 9 November 2026). Monthly prices use 730 hours, 8,760 hours/year and 26,280 hours/3 years; Windows/software/storage/network extra.
TCO: four ways to buy 730 hours/month
At 730 hours/month: D4ps_v5 on-demand $112.42, Spot $23.77, 1-year $66.33, 3-year $42.72; D4s_v5 on-demand $140.16, Spot $29.59, 1-year $86.50, 3-year $55.36. Spot saves $88.65 (D4ps)/$110.57 (D4s) per month vs on-demand; 3-year saves $69.70/$84.80. Spot has the lowest sticker price, but add eviction/recovery, orchestration/checkpointing, disks/network and no-SLA risk.
| Size | On-demand | Spot | 1-year | 3-year |
|---|---|---|---|---|
| D4ps_v5 (Arm) | 112.42 | 23.77 | 66.33 | 42.72 |
| D4s_v5 (x86) | 140.16 | 29.59 | 86.50 | 55.36 |
| Spot monthly saving (D4ps/D4s) | — | 88.65 / 110.57 | — | — |
| Reserved monthly saving (D4ps/D4s) | — | — | 46.09 / 53.66 | 69.70 / 84.80 |
Editorial calculation: 730 hours/month; excludes disks/network/Windows/software/tax; Spot prices vary with supply/demand; reservations cover compute only.
Break-even: eviction frequency × recovery time
Let S be the Spot price, R the effective reservation price, λ evictions per hour and Rt lost/recovery hours per eviction; the effective Spot cost is about S ÷ (1 − λ×Rt). Spot beats the reservation when λ×Rt < 1 − S/R. For the examples: D4ps vs 3-year threshold about 0.444, vs 1-year about 0.642; D4s vs 3-year about 0.466, vs 1-year about 0.658. With 1-hour recovery, a 3-year reservation needs an eviction every 2.1–2.3 hours to win; without checkpoints and 4-hour recovery, one eviction every 8.6–9.0 hours could already favor the reservation.
| Comparison | Threshold 1 − S/R | Meaning (Rt=1h) |
|---|---|---|
| D4ps Spot vs 3-year | about 0.444 | Eviction more often than every 2.25h → reservation |
| D4ps Spot vs 1-year | about 0.642 | Eviction more often than every 1.56h → reservation |
| D4s Spot vs 3-year | about 0.466 | Eviction more often than every 2.15h → reservation |
| D4s Spot vs 1-year | about 0.658 | Eviction more often than every 1.52h → reservation |
| 4-hour recovery (no checkpoint) | Above threshold ÷ 4 | 3-year: one eviction every 8.6–9.0h may flip |
Editorial calculation: S/R from the table; λ×Rt is the hourly loss ratio and must be <1; actual eviction rates vary by region/size/supply—check Azure eviction-rate/price history.
Hidden costs: seven items beyond Spot/reserved prices
Common add-ons: eviction/recovery (lost progress, restart, rerun), checkpointing/orchestration (object storage, queues, scheduling, engineering), Deallocate disks/network continue billing (Delete removes disks but risks data), reservations exclude Windows/software/network/storage (Windows/SQL licenses extra), Spot quota/capacity (separate quota, no capacity guarantee), price volatility/max price (price or capacity can trigger eviction), no SLA/production risk (critical workloads need on-demand/reserved fallback), reserved idle/refund limits (exchange same type; refund cap).
| Cost item | Trigger | Control |
|---|---|---|
| Eviction/recovery | Capacity/price eviction | Checkpoints, idempotency, fast restart |
| Checkpointing/orchestration | Batch/long jobs | Object storage + queues + automation |
| Deallocate disks | Default eviction policy | Use Delete/clean disks as appropriate |
| Windows/software licenses | Not covered by reservation | Separate licenses/AHB; check terms |
| Spot quota/capacity | Tight region/size | Multiple sizes/regions; on-demand fallback |
| Price volatility | Supply/demand | Max price; monitor eviction rate |
| Reserved idle/refund | Downsize/migration | Buy baseline; use exchange/refund limits |
Sources: Azure Spot/reservation docs (9 November 2026). Editorial summary; billing/terms follow official pages and contracts.
How to choose: workload tolerance and commitment
Start with interruptibility: batch, CI/CD, rendering, dev/test, checkpointable HPC → Spot; 24×7 production, SLA/low latency, slow recovery → on-demand or reservations. Then commitment: buy 1/3-year reservations for the stable baseline; 3-year discounts are deeper but lock you in longer; keep on-demand for volatility/new business. Finally mix: reserved baseline, Spot for peaks/interruptible work, on-demand fallback for critical workloads. Check reservation coverage and licensing for Windows/SQL.
| Scenario | Prefer | Check first |
|---|---|---|
| Batch/CI/CD/rendering/dev-test | Spot | Eviction rate, checkpoints, recovery time |
| 24×7 production/low latency/SLA | On-demand or 1/3-year | Capacity, SLA, growth |
| Stable baseline/long term | 3-year reservation | Commitment, exchange/refund terms |
| Moderate certainty/flexibility | 1-year + on-demand | Discount, renewal |
| Peaks/bursty interruptible | Spot + on-demand fallback | Quota, eviction, orchestration |
| Windows/SQL | Reserved compute + separate licenses | AHB/license coverage |
Editorial selection framework, not a vendor recommendation; specifications/availability/compliance follow the business and official docs.
90-day checklist
Use the first 90 days to close “workload tiering → eviction/recovery baseline → reserved baseline → hybrid run → review.” Weeks 1-2: inventory VMs, utilization, SLA, interruptibility; weeks 2-4: pull Spot price/eviction history and calculate λ×Rt; weeks 4-6: checkpoint/restart drills and measure recovery; weeks 6-8: buy 1/3-year reservations for the stable baseline; weeks 8-10: move peaks/batch to Spot with on-demand fallback; weeks 10-12: monitor evictions/cost/coverage and review renewal. Do not decide on “Spot is 79% cheaper” alone.
FAQ
How much can Azure Spot save?
Microsoft says up to 90% off; the D4ps_v5/D4s_v5 examples are about 78.9% off on-demand. Actual prices vary by region/size/supply; the price at order time applies.
Does Spot have an SLA?
No. Spot VMs have no high-availability guarantee; Azure evicts them when capacity is needed or the price exceeds your max, with up to 30 seconds' Scheduled Events notice (best effort).
How much do 1/3-year reservations save?
Examples: D4ps_v5 about 41.0% for 1 year, 62.0% for 3 years; D4s_v5 about 38.3% and 60.5%. Reservations cover VM compute only—not Windows/software/network/storage.
Spot or 3-year reservation?
Use λ×Rt < 1 − S/R: thresholds are about 0.44–0.47 (vs 3-year) and 0.64–0.66 (vs 1-year). Slow recovery/frequent evictions favor reservations; interruptible, fast-recovery workloads usually favor Spot.
Which eviction policy?
Deallocate (default) stops the VM but disks/network keep billing and redeployment is possible; Delete removes disks too (no storage charge but data risk). Choose per workload and clean up.
What do reservations cover?
VM compute only; Windows/software licenses, networking and storage are not included. For Windows/SQL, check licenses/AHB separately—do not treat a reservation as all-inclusive.
Do Spot prices change?
Yes. Spot prices move with supply/demand and VMs can be evicted when the price exceeds your max or capacity is reclaimed. Set a max price, monitor price/eviction rate and keep an on-demand fallback.
Can reservations be refunded/exchanged?
Same-type reservations can be exchanged; refunds have a cap (the official doc cites up to $50,000 in a 12-month rolling window). Estimate the stable baseline before committing.
Research method and limitations
This article separates “official price facts” from “editorial calculations.” D4ps_v5/D4s_v5 on-demand, Spot and 1/3-year reservation prices come from the Azure Retail Prices API (eastus, Linux, 9 November 2026). Spot's 90% cap, 30-second notice, no SLA, eviction policies (Deallocate/Delete) and reservation coverage/exchange/refund come from the Azure Spot product page, Microsoft Learn Spot documentation and Azure reservations documentation. TCO, break-even, hidden costs and the 90-day checklist are editorial.
Eight limitations: (1) only eastus/Linux list prices, excluding tax/discounts/enterprise agreements; (2) 730 hours/month, 8,760/26,280 hours; (3) disks/network/Windows/software/storage excluded; (4) Spot prices and eviction rates vary by region/size/supply and examples are not forecasts; (5) the break-even assumes a stable eviction rate and fixed recovery time, while the real distribution may differ; (6) no real eviction/recovery benchmark; (7) not all VMSS/Compute Fleet/AHB combinations are covered; (8) prices/terms change, so recheck official pages and bills before purchase.
Sources and basis
- Microsoft Azure, Spot Virtual Machines: azure.microsoft.com/en-us/products/virtual-machines/spot. Up to 90% off, no SLA, 30-second notice, suitable workloads. Accessed 9 November 2026.
- Microsoft Learn, Azure Spot Virtual Machines: learn.microsoft.com/azure/virtual-machines/spot-vms. Eviction policy, 30-second notice, quota, price/eviction history. Accessed 9 November 2026.
- Azure Retail Prices API (eastus, Linux): prices.azure.com/api/retail/prices. D4ps_v5/D4s_v5 on-demand/Spot/1-year/3-year prices. Accessed 9 November 2026.
- Microsoft Learn, Azure Reservations: learn.microsoft.com/azure/cost-management-billing/reservations/save-compute-costs-reservations. 1/3-year, coverage, exchange/refund. Accessed 9 November 2026.
Data cut-off 9 November 2026; prices/terms follow the Azure official page and bill; this is not procurement, commercial or legal advice.