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With a 2TB hard drive, an NVR using H.265, and between 4 and 8 4MP cameras recording on motion, typical retention periods are between 15 and 30 days. When using H.264, the same hard drive yields approximately 40% to 50% fewer days of retention. More cameras, higher resolution, or continuous recording all reduce the retention time.
“How long is recorded?” is a question that almost no one asks before installing cameras, and it’s the one that matters most when reviewing something that happened three weeks ago. The answer depends on four things: the size of the hard drive, the number of cameras, the resolution, and the recording codec.
The four factors that define retention days.
Each of these factors either multiplies or divides the final result, so changing just one can double or halve the recording days.
| Factor | Effect during retention periods |
|---|---|
| Disk size | More terabytes, more days, in a direct proportion. |
| Number of cameras | Each additional camera distributes the same disk space across more recordings. |
| Resolution (2MP, 4MP, 8MP) | More resolution, more weight per second, fewer days. |
| Codec (H.264 or H.265) | H.265 uses 40% to 50% less data than H.264, while maintaining the same quality. |
Reference table: typical retention periods
This table assumes recording based on motion detection (not continuous 24 hours), which is the most common setting used in businesses and warehouses.
| Cameras | Resolution | Disc | Codec | Typical days |
|---|---|---|---|---|
| Four cameras | 4MP | 1 terabyte | H.265 | Between 20 and 25 days. |
| Four cameras | 4MP | 2 terabytes | H.265 | Between 40 and 50 days. |
| Eight cameras | 4MP | 2 terabytes | H.265 | Between 15 and 30 days. |
| Eight cameras | 4MP | 2 terabytes | H.264 | Eight to fifteen days |
| Sixteen cameras | 4MP | 4 terabytes | H.265 | Between 12 and 20 days. |
These are ranges, not exact figures: the actual movement of the location (how many people and vehicles are passing in front of each camera) shifts the result within each range.
Why does H.265 significantly alter the account?
The H.265 codec (also known as HEVC) compresses images more efficiently than the previous H.264 codec, while maintaining the same visible quality with fewer data per second. In practice, this means that with the same hard drive, you can achieve 40% to 50% more recording time simply by using an NVR and cameras that support H.265. That’s why, since 2024, virtually all of the new equipment we install is configured by default to use this codec.
I continue through movement.
Continuous recording (24 hours, without stopping) ensures that you never lose a second, but it consumes the disc much faster. Recording triggered by motion significantly reduces the storage space, as it only records when there’s activity in front of the camera, although there’s a minimal margin (one or two seconds) where the sensor detects and begins recording. The practical recommendation: continuous recording for entrances and cabinets, and motion recording for hallways, cellars, and exterior areas with more consistent traffic.
How to calculate what you need before installing.
Instead of buying the largest available disc “just in case,” it’s more sensible to start with a question: how many days do you need to be able to go back and review? If the answer is “one month,” then the disc and codec are sized for that purpose from the outset – they aren’t adjusted later once the system is installed and recording less than anticipated.
How much does it cost to expand the storage?
If the system is already installed and recording fewer days than you require, the most direct solution is usually to replace the hard drive with one of greater capacity, rather than replacing the entire NVR. A 2TB hard drive designed for continuous video surveillance recording (different from a generic computer hard drive, which isn’t built to write 24 hours a day) is the most common upgrade we offer. And in most 4 or 8-channel NVRs, there’s a second empty bay available to add it without removing the existing drive.
What to check if a disk fills up sooner than expected.
When a system records fewer days than calculated, it’s almost always due to one of these causes, in order of frequency:
- It was set to continuous recording. Instead of as a movement, without anyone having requested it that way.
- Cameras were added afterward. without recalculating how much space the entire system needs.
- The motion detection sensitivity is very high.And the system records with every branch that moves in the wind in front of the camera.
The three of them are troubleshooting by reviewing the NVR’s settings, without purchasing any new equipment. This is part of the maintenance check we perform.
Our service
At Ditap Seguridad, every… CCTV installation It includes an NVR sized according to how many days of recording you need, configured by default with H.265. If you already have a system installed and aren’t sure how many days of footage it’s actually storing, we’ll review it as part of our service. camera monitoring.
September 2026 editorial archive. The figures are historical references, not current prices or service commitments. Please refer to a proposal tailored to your location.
Frequently Asked Questions
Why is my system recording fewer days than I expected?
It’s almost always one of three things: it’s recording continuously instead of on motion, it’s using H.264 instead of H.265, or there are more cameras connected than the storage space was intended to handle.
Is it better to record continuously or only when motion is detected?
Moving lighting provides more operating hours, but it can lose seconds if the sensor takes a moment to activate. For critical access points, continuous activation is recommended; for hallways and walkways, motion activation is sufficient.
Can the drive be expanded after it has been installed?
Yes, if the NVR has available bays, it’s best to order a recorder with more capacity than you actually need on the first day.
