Office 2021 vs Microsoft 365：买断密钥还是订阅？
真实成本分析 — 什么时候永久 Office 2021 密钥胜过订阅，什么时候 365 更合理。
Microsoft sells Office two ways: a perpetual license (Office 2021 — buy once, use forever on one PC) and a subscription (Microsoft 365 — monthly/annual, always updated, multiple devices). They look similar but the economics diverge fast.
| Office 2021 | Microsoft 365 | |
|---|---|---|
| Payment | One-time key | Monthly / annual subscription |
| Apps included | Word, Excel, PowerPoint, Outlook | Same + always latest version |
| Major upgrades | No — stuck on 2021 forever | Yes — every new release |
| Devices | 1 PC | 1–6 users, 5 devices each |
| Cloud storage | — | 1 TB OneDrive per user |
| End of support | Ended Oct 13, 2026 | Continuous |
When Office 2021 wins
If one PC needs Word/Excel/PowerPoint and you plan to keep it 2+ years, the one-time key pays for itself versus roughly a year and a half of 365 Personal — and keeps working after that for free. It is also the only option for offline/air-gapped machines and environments where subscriptions are administratively annoying. One caveat: Office 2021 support ended October 13, 2026 — the apps keep working indefinitely, but no more security patches. For supported perpetual builds, look at Office 2024 keys instead.
When Microsoft 365 wins
- •Multiple devices (PC + laptop + tablet)
- •Need OneDrive storage bundled
- •Want new features as they ship (e.g., the AI tooling lands in 365 first)
- •Businesses that want predictable opex instead of capex
Reseller note
For bulk resale, perpetual Office 2021 keys are the volume seller — buyers search for the one-time option specifically to escape the subscription. MAK editions add multi-seat activation on top.