People debate NAS versus cloud storage as if it is a philosophical question. It is mostly an arithmetic question. Here I run the numbers at three storage scales, using current prices and realistic hardware assumptions. Prices are in GBP; adjust the exchange rate for your region, but the ratios hold.
Assumptions
- Cloud prices: Backblaze B2 (£0.005/GB/month), Cloudflare R2 (£0.015/GB/month for storage, egress free), Wasabi object storage (£0.006/GB/month). Consumer services (iCloud, Google One) are priced per tier.
- NAS hardware: entry-level 2-bay (Synology DS223, ~£280) for 8 TB scale; 4-bay (QNAP TS-453E, ~£420) for 20–50 TB scale. Higher-end DIY TrueNAS build for 50 TB.
- Drives: refurbished enterprise HDDs at approximately £15/TB delivered. Configured in RAID-1 (2-drive mirror) or RAIDZ1 (4-drive with one parity) for usable capacity.
- Power: 10W–20W average for a NAS at UK electricity rates (~£0.29/kWh). Five years of 15W continuous draw = ~£190.
- Failure provision: budget one drive replacement per five years at £15/TB.
8 TB usable storage (household photos/media)
| Option | Year 1 | Year 2 | Year 3 | Year 4 | Year 5 | Total |
|---|---|---|---|---|---|---|
| iCloud (2 TB plan) | £108 | £108 | £108 | £108 | £108 | £540 |
| Backblaze B2 | £480 | £480 | £480 | £480 | £480 | £2,400 |
| NAS (DS223 + 2×6TB) | £460 | £38 | £38 | £38 | £53 | £627 |
At 8 TB the NAS hardware cost is lower than a single year of Backblaze B2. By year two the NAS is already £820 cheaper in cumulative spend, and the gap widens every year after that. The iCloud row is not a direct comparison: that £108/year buys a 2 TB plan, not 8 TB of storage. Matching iCloud at 8 TB would require the 12 TB plan at around £432/year, which makes cloud storage even less competitive on cost. The NAS’s actual advantages here are privacy, local access speed, and no ongoing subscription.
20 TB usable storage (media server + family photos)
| Option | Year 1 | Year 2 | Year 3 | Year 4 | Year 5 | Total |
|---|---|---|---|---|---|---|
| Backblaze B2 | £1,200 | £1,200 | £1,200 | £1,200 | £1,200 | £6,000 |
| Cloudflare R2 | £3,600 | £3,600 | £3,600 | £3,600 | £3,600 | £18,000 |
| NAS (4-bay + 4×8TB RAIDZ1) | £900 | £55 | £55 | £55 | £70 | £1,135 |
At 20 TB the NAS is already cheaper than B2 in year one (£900 vs £1,200) and costs less in total over five years by a factor of more than five. Against Cloudflare R2 the gap is enormous: £1,135 versus £18,000. Egress costs are not included in the cloud figures; if you stream your own media library from cloud storage, costs increase substantially further.
50 TB usable storage (photography archive + video)
| Option | Year 1 | Year 2 | Year 3 | Year 4 | Year 5 | Total |
|---|---|---|---|---|---|---|
| Backblaze B2 | £3,000 | £3,000 | £3,000 | £3,000 | £3,000 | £15,000 |
| Wasabi object storage | £3,600 | £3,600 | £3,600 | £3,600 | £3,600 | £18,000 |
| DIY TrueNAS (8×14TB RAIDZ2) | £1,650 | £95 | £95 | £95 | £120 | £2,055 |
At 50 TB the NAS wins from year one. The five-year B2 bill is roughly seven times the total NAS cost; Wasabi is nearly nine times. At this scale the cost case for cloud per-GB object storage is simply not there.
What the numbers miss
Cost is one dimension. A few factors the tables do not capture:
Your time
A NAS requires maintenance: OS updates, monitoring, replacing failed drives, occasional configuration. If your time has a meaningful cost or you simply do not want to spend it on infrastructure, that is a legitimate reason to prefer a managed service.
Off-site backup
A NAS at home addresses the “local copy” requirement of the 3-2-1 rule but not the off-site requirement. A complete backup strategy for a NAS requires a separate off-site solution (a second NAS at a family member’s house, or a cloud backup service for the most critical subset of data). This adds cost — typically £5–20/month for critical data on Backblaze B2 with restic.
Risk profile
A NAS drive failure in a RAID configuration does not lose data, but it is a stressful event that requires attention. Hardware failure, fire, flood, or theft can destroy a NAS. Cloud services have geographic redundancy by default. Quantifying this in pounds is difficult, but it is a real consideration for genuinely irreplaceable data.
Conclusion
Run the per-year numbers and a NAS is cheaper than per-GB object storage at every scale from 8 TB upwards — often from year one. Cloud storage’s real advantages are not cost: they are convenience, geographic redundancy with no hardware to maintain, and no single point of physical failure. For genuinely irreplaceable data that you cannot afford to lose to a house fire or theft, those properties have real value regardless of price. For bulk media libraries that can be reconstructed from source files, they rarely justify the ongoing spend.
The pragmatic answer for most people: use a NAS for the bulk of local data, and a cheap cold-storage cloud service for the off-site backup copy of the most critical subset only. This gives you 3-2-1 compliance at a fraction of the cost of storing everything in the cloud, without paying per-GB every time you access your data.