Buying guide · 5 min read
How much storage
does CCTV need?
'How many days does it record?' is the second question every customer asks. Here are the real numbers, and the settings that change them.
The maths
Storage is bitrate × time. A camera's bitrate depends on resolution, frame rate, codec and how much is happening in the scene. Sensible H.265 settings give roughly: 4MP ≈ 2–4 Mbps, 8MP ≈ 4–8 Mbps. One megabit per second for a day is about 10.5 GB.
| Cameras | 30 days | 60 days | 90 days |
|---|---|---|---|
| 4 × 4MP | ~2 TB | ~4 TB | ~6 TB |
| 4 × 8MP | ~4 TB | ~8 TB | ~12 TB |
| 8 × mixed (4×8MP + 4×4MP) | ~6 TB | ~12 TB | ~18 TB |
| 16 × 8MP | ~16 TB | ~32 TB | ~48 TB |
These assume continuous recording with H.265 and moderate activity. Real numbers vary — a busy shop front uses more than a quiet garden.
Settings that halve storage without losing detail
- H.265+ (Hikvision's optimised codec): typically 30–50% saving over H.264 on static scenes.
- Event-plus-continuous: low bitrate normally, full bitrate when a person or vehicle is detected.
- Frame rate: 12–15 fps is plenty for security; 25 fps doubles storage for no evidential gain.
- Don't over-resolve: 4MP on the positions that don't need 8MP — see 4MP vs 8MP.
How long should you keep footage?
30 days is the usual standard for homes and most businesses. Licensed premises, insurers and some landlords ask for longer. For businesses, retention is also a GDPR question: keep it as long as you need and no longer, and write it down.
The drive itself
Use surveillance-rated drives (built for continuous writing) not desktop drives. Expect to replace drives every 3–5 years — a service visit checks their health before they fail silently.
30 days at full quality on every camera as standard, with headroom; 60–90 days where a policy or insurer requires it.
Your property decides. Not the logo.
Questions
Good to know.
Does the NVR stop when the drive is full?
No — it overwrites the oldest footage automatically.
Can I add cloud backup?
Yes, for selected clips or cameras. Full continuous cloud recording is expensive and broadband-dependent; local first, cloud as a copy.
What if the recorder is stolen?
Hide and lock it, and consider a small cloud clip backup for the most important camera.