How Much Storage Does a CCTV System Need? (Calculator + Real-World Examples)

Most people underestimate CCTV storage. And most vendor calculators make it worse by using theoretical maximum bitrates that real cameras never hit. A 4-camera home system on realistic H.265 settings needs roughly 4-5 TB of usable storage for 30 days of footage. A 16-camera retail system needs closer to 20 TB. A 32-camera warehouse deployment with mixed 4K and standard cameras can push past 50 TB. This guide calculates real storage requirements from first principles. Resolution, codec, framerate, recording mode, retention period, and RAID overhead. With three worked examples covering home, retail, and large commercial deployments. Australian pricing and NVR software notes are in the AU section below.

Why Vendor Storage Calculators Get It Wrong

Camera manufacturers and NVR vendors typically quote storage requirements using maximum bitrate figures. The highest data rate their hardware is capable of, not what it produces under normal conditions. A camera rated at 16 Mbps maximum rarely streams above 6-8 Mbps in a typical residential installation. Using the manufacturer's maximum figure results in storage estimates 2-3 times larger than you actually need.

The opposite mistake is using overly optimistic compression assumptions. H.265 (HEVC) does reduce storage by roughly 40% compared to H.264 at equivalent quality, but only when both the camera and the NVR or NAS software are actually encoding in H.265. Many budget cameras advertise H.265 support but default to H.264 in their firmware. Check your NVR software stream settings before planning storage around H.265 savings.

The Variables That Drive Storage Consumption

Resolution and Codec. The Biggest Levers

Resolution and codec together account for the largest share of storage variation. The table below shows realistic average bitrates per camera at 15 fps. The baseline used in storage planning. These are real-world averages from typical installations, not theoretical maximums.

Framerate also matters. The figures above assume 15 fps. A common surveillance default that balances motion clarity with storage efficiency. Running at 30 fps roughly doubles storage consumption compared to 15 fps. For most surveillance use cases (perimeter monitoring, retail floor coverage), 15 fps captures usable evidence footage. Reserve 25-30 fps for high-activity areas like tills or entry gates where motion detail matters.

Recording Mode. Continuous vs Motion-Only

Continuous recording captures everything, all the time. It is the most reliable approach for compliance and evidence purposes. You never miss an event because the motion detection failed. The trade-off is storage: a camera running continuously for 24 hours generates roughly 37 GB per day at 4MP H.265 and 15 fps.

Motion-only recording triggers recording when the camera detects movement and can reduce storage to 30-60% of continuous recording, depending on scene activity. The risk is missed events if the motion detection is poorly calibrated. A common issue with budget cameras that use basic pixel-comparison detection rather than AI-based object detection. For any system where footage may be needed as evidence, the Need to Know IT team recommends continuous recording on key cameras (entry/exit points, tills, car parks) with motion-only acceptable for low-traffic areas (back corridors, storage rooms).

Retention Period

Retention period is a direct multiplier on storage. Going from 14 days to 30 days doubles storage need; going from 30 to 60 days doubles it again. For home use, 14-30 days is typical. Enough to catch anything that happens over a holiday period. For business use, 30 days is the most common default. Some industries in Australia have specific requirements: retail and hospitality often operate on 30-day cycles; construction sites, aged care facilities, and environments covered by workplace health and safety obligations may need 60-90 days. Check your insurer's requirements before settling on a number. Some policies require minimum retention periods for claims to be valid.

RAID Level. Redundancy Overhead

RAID adds drive overhead on top of the raw storage requirement. RAID 1 (mirroring) doubles raw capacity needed. A 5 TB usable requirement needs 10 TB of raw drives. RAID 5 (single parity, minimum 3 drives) adds approximately 33-50% overhead depending on drive count. RAID 6 (dual parity, minimum 4 drives) is the right choice for larger systems where a rebuild after a single drive failure while carrying another failing drive is a real risk. For a detailed explanation of the RAID overhead calculations, see the RAID Usable Capacity Calculator.

Three Real-World Scenarios

Scenario 1. 4-Camera Home System

A typical home setup: 4 cameras covering front door, driveway, back yard, and a side gate. 4MP resolution, H.265, 15 fps, continuous recording 24 hours per day, 30-day retention, RAID 5, 15% headroom buffer. This is the most common configuration for a purpose-built home NAS surveillance setup using something like a Synology DS425+ or QNAP TS-464.

Three 4 TB surveillance drives in RAID 5 gives 8 TB usable. Comfortable headroom above the 5 TB requirement. At 14 Mbps total bandwidth, this setup runs comfortably on any gigabit home network with no dedicated VLAN required. See the AU section below for current Australian pricing on WD Purple drives from Mwave and Scorptec.

Scenario 2. 16-Camera Retail Store

A medium retail store. 16 cameras covering the sales floor, storage areas, entry/exit points, and car park. All cameras at 4MP H.265, 15 fps, continuous recording, 30-day retention (standard for retail insurance requirements), RAID 5 across 4 drives, 15% headroom. The NAS would typically be a 4- or 6-bay unit running Synology Surveillance Station or QNAP QVR Pro. See the NAS Surveillance Camera Compatibility Guide for platform comparison.

Four 8 TB surveillance drives in RAID 5 provides 24 TB usable, comfortably above the 20 TB requirement with room for retention extensions. WD Purple 8 TB drives retail around $279-$299 each at Australian retailers. Budget approximately $1,100-$1,200 for drives. At 56 Mbps total camera bandwidth, a dedicated PoE switch and surveillance VLAN is worth setting up to keep camera traffic off the main business network. The NAS Power Calculator can estimate the running cost of this configuration. A 4-bay NAS with 8 TB drives running 24/7 typically costs $120-$180 per year in electricity at average Australian tariffs.

Scenario 3. 32-Camera Warehouse or Multi-Site

A larger commercial deployment: 32 cameras across a warehouse or multi-building site. Mixed resolution. 8 cameras at 4K covering loading docks and entry points where detail matters, 24 cameras at 4MP H.265 for general coverage. Continuous recording, 30-day retention, RAID 6 (dual parity. The right choice at this scale where a single drive failure during a rebuild is a real risk), 15% headroom buffer.

Six 16 TB surveillance drives in RAID 6 gives 64 TB usable. The headroom above 50 TB matters here because footage retention may need to be extended for insurance or compliance reasons without a full storage rebuild. At 140 Mbps total camera bandwidth, this setup requires a dedicated gigabit PoE switch. Standard gigabit is not a bottleneck at this bandwidth, but isolation from other network traffic is essential. For multi-site deployments, consider whether centralised storage at a single location or distributed NAS at each site better fits the network topology and NBN upload speed limitations.

Drive Selection: Why Surveillance Rated Matters

Surveillance workloads are unlike standard NAS file storage. Cameras write continuously, 24 hours a day, 7 days a week, with very little read activity. This sequential write pattern differs fundamentally from desktop drive usage. Desktop drives are designed for bursty workloads with regular idle periods, not sustained multi-day write cycles. Running desktop drives in a surveillance NAS will work initially, but failure rates are significantly higher than with drives designed for the application.

The two surveillance-specific product lines designed for this workload are Seagate SkyHawk and WD Purple. Both are rated for 24/7 operation, support AllFrame or rotational vibration compensation features used by multi-drive NAS enclosures, and carry the longer MTBF ratings appropriate for continuous write workloads. Standard desktop drives. Even NAS-grade drives. Are not rated for the continuous sequential write profile of surveillance recording and will show higher failure rates in this workload. AU retailer availability is covered in the Australian buyers section below.

Network Bandwidth and What It Means for Your Infrastructure

Every camera is a constant stream of data on your network. The bandwidth calculation is straightforward: bitrate per camera multiplied by camera count. For the scenarios above: 4 cameras at 14 Mbps is trivial on any modern network; 16 cameras at 56 Mbps is manageable on gigabit but warrants a dedicated VLAN; 32 cameras at 140 Mbps on a shared gigabit network will cause congestion issues that affect both surveillance reliability and other network services.

Remote viewing requirements depend on your upload speed and whether your ISP uses CGNAT. Both Synology Surveillance Station and QNAP QVR Pro support sub-stream transcoding to reduce remote access bitrate requirements. NBN-specific notes are in the Australian buyers section below.

Rules of Thumb for Quick Planning

If you need a quick estimate before running the full calculator, these rules of thumb are accurate enough for initial planning. All assume H.265 encoding at 15 fps, continuous recording, and 15% headroom buffer.

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🇦🇺 Australian Buyers: What You Need to Know

Where to Buy Surveillance Drives

Seagate SkyHawk and WD Purple surveillance drives are stocked at Scorptec, Mwave, and PLE. Current AU pricing for WD Purple 4 TB runs approximately $139-$159; WD Purple 8 TB approximately $239-$279. Seagate SkyHawk is similarly priced. For NAS-based NVR enclosures (Synology DS425+, QNAP TS-464), check the NAS buying guide for current AU pricing.

NBN and Remote Viewing

On an Australian NBN 100/20 connection, upload speed is limited to 20 Mbps. Not enough to stream multiple 4MP camera feeds remotely. Both Synology Surveillance Station and QNAP QVR Pro support sub-stream transcoding to lower-quality remote streams, which resolves this in most home and small business setups. CGNAT. Common on fixed wireless NBN, satellite NBN, and some budget MVNOs. Blocks direct inbound connections. Use our NBN Remote Access Checker to confirm whether your connection supports direct remote NVR access, or whether you need QuickConnect, Tailscale, or a reverse proxy.

Related reading: our NAS buyer's guide.

How much storage do I need for 4 cameras at 1080p for 30 days?

At 1080p with H.265, 15 fps, continuous 24/7 recording: approximately 2.2 TB usable before RAID overhead. With 15% headroom and RAID 5 across 3 drives, a 3× 2 TB configuration (4 TB usable) covers this comfortably. Switching to H.264 increases that to approximately 3.5 TB usable before RAID. Use the NVR Storage Calculator to model your exact settings.

What is the difference between H.264 and H.265 for surveillance storage?

H.265 (also called HEVC) uses approximately 40% less storage than H.264 at equivalent image quality. For a 4-camera system running 30 days, this is the difference between roughly 3.5 TB and 2.2 TB usable storage. H.265 requires that both the camera and the NVR/NAS software support it. Many budget cameras advertise H.265 but default to H.264 in firmware settings. Check the stream configuration in your NVR software before planning storage around H.265 savings.

Do I need RAID for a home CCTV system on a NAS?

Not strictly, but it is recommended for any system you depend on. Without RAID, a single drive failure means lost footage and downtime until the drive is replaced and recording resumes. RAID 1 (two drives mirroring each other) is the simplest option. A drive failure triggers an alert but recording continues uninterrupted. For a budget home system, some users accept the single-drive risk to maximise usable storage capacity. For any business or compliance use, RAID is not optional. See the NAS RAID Explained guide for a full breakdown of RAID levels and when each applies.

How long should I keep CCTV footage in Australia?

There is no single national requirement. Retention obligations depend on industry, business size, and state or territory legislation. For home use, 14-30 days is typical. For business use, 30 days is the most common default. Retail, hospitality, and aged care often operate under specific obligations. Check with your industry association or insurer. Some insurance policies require minimum retention periods for surveillance footage to be valid as evidence in a claim. The Privacy Act 1988 applies to businesses with annual turnover above $3 million and requires that personal information (including surveillance footage) is not kept longer than necessary. So longer isn't always better from a compliance perspective.

Can I use desktop hard drives in a surveillance NAS?

You can, but it is not recommended for any system you rely on. Desktop drives are not rated for continuous 24/7 write workloads. The sustained sequential write pattern that surveillance creates is significantly harder on drives than typical desktop usage. Surveillance-rated drives (WD Purple, Seagate SkyHawk) are engineered for this workload and carry appropriate MTBF ratings. At 4 TB, the price difference between a desktop drive and a WD Purple is typically $20-$30. Not enough to justify the reliability risk for a system that records security footage.

Can I back up CCTV footage to the cloud on an Australian NBN connection?

For full continuous backup of all camera streams: generally not practical. A 4-camera system at 4MP H.265 produces approximately 147 GB of footage per day. A standard NBN 100/20 connection with 20 Mbps upload would take approximately 16 hours to upload a single day's footage. Leaving no spare upload capacity for anything else. A realistic approach is selective cloud backup: clip key events (motion triggers or manual flagged footage) rather than full stream backup. Most NVR platforms including Synology Surveillance Station support automated clip upload to cloud storage for exactly this use case.

If you're still deciding on a brand, our Synology vs QNAP comparison guide breaks down which platform suits different use cases in Australia.

Is a NAS better than a dedicated NVR for storage planning?

A dedicated NVR (Network Video Recorder) is simpler. It is purpose-built for surveillance and comes preconfigured for the workload. A NAS running Synology Surveillance Station or QNAP QVR Pro is more flexible. The same device handles file storage, photo backup, and other services alongside surveillance. The storage planning maths is identical either way: the same cameras, the same bitrates, the same retention requirements. The NVR Storage Calculator works for both approaches. The main NAS advantage is flexibility; the main NVR advantage is simplicity and plug-and-play camera compatibility. See the Best NAS for Surveillance Australia guide for a comparison of recommended models.