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

CPU generation

RAM (GB)

Drive bays available How many HDDs/SSDs can you install?

Known idle power draw (W, optional) Measure with a power meter, or leave blank

Electricity rate (c/kWh) AU average ~30-35 c/kWh

Intended use

Your Old PC (DIY NAS)

Est. idle power—

Annual power cost—

5-year power cost—

Drive bays—

Hardware costA$0 (repurposed)

5-yr total cost—

Dedicated NAS

Typical idle power—

Annual power cost—

5-year power cost—

Drive bays—

Hardware cost (est.)—

5-yr total cost—

Recommended dedicated NAS alternative

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How we calculate this

Your PC’s idle power draw is either the wattage you measured yourself with a power meter, or an estimate based on typical idle wattage for your selected CPU generation, drawn from real-world reviews of desktop systems without a discrete GPU. Annual electricity cost is calculated as watts times 8,760 hours in a year, divided by 1,000 to convert to kWh, multiplied by your electricity rate.

The dedicated-NAS comparison column uses real current-generation NAS models matched to your selected use case and bay count, with published idle wattage figures and approximate AU retail hardware cost. The 5-year total for each side adds five years of electricity cost to the one-time hardware cost, zero for your existing PC since it is already owned.

The verdict weighs three things: whether your PC meets the bare minimum for the NAS software you would run (RAM and drive bays), whether its power cost makes it more expensive than buying a dedicated unit over 5 years, and any use-case-specific caveats. For example, older CPUs without hardware video transcoding are flagged separately for Plex use, since software transcoding pushes real-world power draw well above idle.

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.