Is My Old PC a Good NAS? Cost & Performance Calculator

This old PC as NAS cost and performance calculator assesses whether repurposing an existing computer as a NAS makes financial sense compared to a dedicated unit. Factors in power draw, idle wattage, Australian electricity costs, and hardware compatibility.

Old PCs can make capable DIY NAS servers, but power draw is the hidden killer. An old desktop idling at 60-80W costs significantly more to run per year than a dedicated NAS idling at 6-15W. Enter your PC specs and see if the maths works out.

Your Old PC

How many HDDs/SSDs can you install?
Measure with a power meter, or leave blank
AU average ~30-35 c/kWh

Your Old PC (DIY NAS)

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Hardware costA$0 (repurposed)
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Dedicated NAS

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Recommended dedicated NAS alternative

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Frequently Asked Questions

How much does it actually cost to run an old PC 24/7 versus a NAS?
An old desktop PC from 2014-2018 typically idles at 40-80W depending on the CPU and whether there's a discrete GPU. At Australian electricity rates of ~32c/kWh, 60W running 24/7 costs approximately A$168/year. A dedicated NAS like the Synology DS425+ idles at around 18-22W, about A$52/year. Over 5 years the difference is roughly A$580 in electricity alone. On top of that, dedicated NAS appliances have sleep/disk-spin-down features that reduce real-world power further, while many old PCs don't support proper S3/S4 sleep in NAS-OS configurations.
What NAS operating systems can I run on an old PC?
TrueNAS CORE (FreeBSD-based, ZFS, excellent for storage) and TrueNAS SCALE (Linux-based, adds Docker/Kubernetes) are the most popular for x86 hardware. Both are free and open-source. Unraid is another option (~USD $49-129 one-time licence), it's more flexible with mixed drive sizes. OpenMediaVault (Debian-based) is lighter weight and suitable for less powerful hardware. All of these require at least 8 GB RAM, preferably 16 GB for ZFS. TrueNAS CORE requires ECC RAM for production ZFS deployments.
Does my old PC have enough RAM for a NAS OS?
For basic file sharing with Samba, 4 GB is sufficient with OpenMediaVault or TrueNAS CORE in minimal config. For ZFS with a meaningful ARC cache (improves read performance), 8 GB is the practical minimum: 16 GB is recommended. For Plex transcoding, add ~2 GB per simultaneous 1080p transcode on top of OS requirements. For VMs and containers (Proxmox, TrueNAS SCALE), 16-32 GB is recommended. 4K HDR transcoding on Plex without hardware acceleration is CPU-intensive and may require a modern multi-core processor regardless of RAM.
Can I run Plex on an old PC NAS?
Yes: Plex is one of the strongest use cases for a PC-based NAS over a dedicated appliance. Even a 6th-8th gen Intel Core i3/i5 with Intel Quick Sync can hardware-transcode 4K HEVC streams, which a budget NAS cannot. The caveat is power draw: Plex NAS boxes tend to idle at 15-25W with Quick Sync, which is acceptable. Older CPUs without hardware transcoding (pre-6th Gen Intel, or AMD without VAAPI/NVENC) will consume significantly more CPU for software transcoding and push idle-equivalent power much higher during active Plex use.
What's the main reason not to use an old PC as a NAS?
Power consumption. Dedicated NAS appliances are engineered for minimum idle draw, typically 8-22W for a 4-bay unit. Most old desktop PCs idle at 40-100W even without a discrete GPU. Over 3-5 years this difference pays for a new dedicated NAS. Secondary reasons include fan noise (most desktops are louder than NAS units), form factor (rack/shelf placement), and the lack of hot-swap bays on standard PC cases. That said, for Plex/VM workloads where a dedicated NAS would underperform anyway, a power-efficient modern mini PC or refurbished workstation is often the right answer.