Synology or Build? The Five-Year NAS Cost

A four-bay Synology and a four-bay box you assemble yourself both sit in a cupboard drawing power every hour for five years. Everyone assumes the DIY one is cheaper to run and that the electricity is where the appliance premium comes back. Neither half of that is true.

The NAS operating system comparison ends by saying all four appliances are wrong if what you want is a machine you administer yourself. This page is that purchase, costed: what does five years of each actually take out of your account, drives excluded?

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The five-year number

Drives are excluded from every row because they are the same purchase either way — four 8TB NAS drives cost what they cost whichever box they go in. What is left is the enclosure, the memory, a boot device where one is needed, the operating system, and sixty months of electricity.

The DIY build is $323 to $347 cheaper across five years, and electricity accounts for $32 to $56 of that. Roughly a tenth. The rest is the box price and the fact that DSM is included while an Unraid licence is not.

Buy the most expensive Unraid tier and the DIY route still finishes $74 to $98 ahead. That is the whole electricity argument, resolved: it is a rounding error against a $291 difference in sticker price.

What the boxes actually draw

These are NAS Compares’ measurements, taken with the drives installed and the array built:

Rob Andrews at NAS Compares recorded the DS925+ at “approximately 28 watts” in a fully idle state, base apps installed and the system not being accessed, rising to 62–64W with all four bays filled, SSDs in, the CPU under strain and both 2.5GbE connections active (review, 2 May 2025). The WTR Pro review of 11 September 2024 gives “an average of 21-24W when the drives and system were in Idle”, and 64–66W with the drives being read and the CPU at 40–50%. The array in that review was four Seagate IronWolf 4TB drives in a one-disk-redundancy ZFS pool under Unraid, stated in the throughput section rather than beside the idle figure.

Note what the load column does. Under actual work the appliance and the DIY box land within two watts of each other. The idle spread is the entire difference, and the idle spread is worth $6 to $11 a year.

Building your own does not lower the idle draw

This is the part that gets assumed and is wrong often enough to cost people money.

The same reviewer, same method, measured the Topton MW-N100-NAS — the six-SATA, 10GbE ITX board a parts-built four-bay usually starts from — at “around 28.2W with drives connected.” That is the Synology’s figure to a tenth of a watt, from a board whose CPU carries a 6W TDP. The N305 version of the same board recorded “idle power consumption of just 27-28 watts with six connected drives in hibernation” — with the drives parked, which should have been the best case.

A 6W processor does not produce a 6W machine. The SATA controller, three network interfaces and the board’s own power delivery set the floor, and on these boards the floor is high. If low idle is the goal, the board is the wrong place to look for it. The laptop-class SoC in the AOOSTAR box is what buys the 21W, not the fact that you assembled it.

Our idle power reference for homelab hardware has the wider device-by-device table if you are budgeting a whole rack rather than one NAS.

The setting that beats both boxes

Synology publishes its own numbers, and they disagree with the measured one in a way worth understanding rather than averaging.

The DS925+ product specification, last updated 6 August 2026, lists 37.91 watts (Access) and 12.33 watts (HDD Hibernation). NAS Compares measured 28W. None of these three contradicts the others, because they describe three different machines-in-a-moment: drives spinning and being read, drives spun up but nothing being served, drives parked.

Priced over five years at $0.184/kWh:

That $206 swing on one machine is between three and a half and six times the $32-to-$56 gap between the two machines. Whether your drives get to park matters more than which enclosure you bought, and it is the only power lever on this page big enough to notice.

It is also the lever most people never pull. Anything that touches the array on a timer — a surveillance recorder, a container writing logs, a backup client polling every few minutes, a media server refreshing metadata — wakes the drives and keeps them awake. Hibernation is a real setting and mostly a theoretical saving. Assume the 28W figure, run the numbers in the power cost calculator against your own utility rate, and treat anything better as a bonus.

What the $291 buys, and what it does not

The gap in the hardware column is $889.99 against $379.00 for the AOOSTAR barebone, plus $129.99 for a 16GB DDR4-3200 SO-DIMM and $89.99 for a boot NVMe the Synology does not need, since DSM installs onto the array.

For that $291 you get DSM, a three-year warranty you can extend to five by buying an extension, and a support line. You do not get more hardware. The DS925+ ships 4GB of DDR4 ECC against the DIY box’s 16GB, an embedded Ryzen V1500B against a Ryzen 7 5825U, and two 2.5GbE ports against two 2.5GbE ports.

Three constraints ride along with the appliance, all of them from Synology’s own documents:

• M.2 is still closed. The DSM 7.3 announcement of 8 October 2025 reopened third-party drives for storage pools on 25 model year units, and its footnote reads: “Creation of M.2 based storage pool and cache still requires drives on the HCL.” The specification sheet says the same. A Synology SNV3410-400G listed at $474.99 on Newegg on 7 September 2026; a 512GB ADATA Legend 710 you cannot use for that pool listed at $89.99 in the August feed.
• Memory expansion is conditioned. The DS925+ specification states Synology “will not provide complete product warranty or technical support if non-Synology memory modules are used for memory expansion.” Going past 4GB means buying their module or accepting that.
• No hardware transcoding, at all. The specification sheet lists no video transcoding section for the DS925+, and none for the cheaper DS425+ either. The drive policy got walked back in a point release. This one did not, and it is the change on the 2025 Plus line that deserved the attention the drive policy got. If transcoding is why you are shopping, the NAS transcoding guide sorts the field by that spec alone.

Synology-branded drives cost real money over the equivalent Exos for no benefit I can identify. That was the drives. The M.2 price above is the same policy, still in force.

Build it and run TrueNAS

Buy the AOOSTAR WTR Pro 5825U barebone, a 16GB DDR4-3200 SO-DIMM and a cheap boot NVMe, and put TrueNAS on it. That is $598.98 in hardware, nothing for the operating system, and $169 to $193 of electricity over five years. It gives you four times the memory, a genuinely faster processor, ZFS checksumming instead of Btrfs on a locked appliance, any NVMe you like in the M.2 slots, and a machine you can repurpose when your storage needs change.

Pay for Unraid instead of TrueNAS if your drives are mismatched sizes and you want to add one at a time — $49 Starter caps at six storage devices with one year of updates, $249 Lifetime is unlimited devices and updates forever. Even the expensive tier keeps the DIY route ahead on five-year cost. It just stops being the obvious call.

The budget NAS build guide has the full parts list, the recertified-drive route, and what the memory shortage did to every line of it.

Buy the DS925+ if DSM is the product

Synology still makes the best NAS operating system. Not the hardware. Not the drive list. The software, which is what you are still using at month eight.

Buy the DS925+ if you want an appliance that works the day it arrives, an app catalogue that does not run out, and a phone number when it breaks. You are paying $291 up front and $6 to $11 a year more in electricity for exactly that, and it is a defensible purchase — it is just not a cheaper one, and no power calculation is going to make it one.

The cheaper door into DSM is the DS425+ at $599.99 — within a dollar of the DIY build’s hardware total, and Synology’s sheet for it lists a Celeron J4125, 2GB of non-ECC memory and no transcoding section. It closes the price gap by giving up the hardware.

Prices move, the memory market in 2026 moves weekly, and two of these listings carry marketplace sellers. Read the seller name before the price.

Wrong for

The DIY build is wrong if you want an app catalogue rather than a compose file, if nobody in the house can restore a pool at 11pm, or if you were counting on a support contract.

The DS925+ is wrong if you need hardware transcoding, if you want a third-party NVMe cache, or if you are buying it because someone told you the appliance pays for itself in electricity. It does not. At the measured wattages it costs $6 to $11 a year more to run than the box it is already more expensive than.

Both are wrong if you are choosing on power alone. Across every machine on this page the five-year electricity spread is $169 to $227 — under sixty dollars end to end. Choose on the software, the drive policy and the sticker, then set your utility rate in the power calculator and stop thinking about it.

Sources

• NAS Compares — Synology DS925+ NAS Review, 2 May 2025 — measured idle and load draw, noise, thermals
• NAS Compares — Aoostar WTR Pro NAS Review, 11 Sep 2024 — measured idle and load draw with four IronWolf 4TB drives
• NAS Compares — Topton MW-N100-NAS motherboard review (14 Nov 2024, updated 4 Dec 2024) and MW-N305-NAS review, 4 Dec 2024 — measured ITX board idle draw
• Synology DS925+ specifications and the product specification PDF, last updated 6 Aug 2026 — published wattages, memory and M.2 conditions, warranty
• Synology DS425+ specifications — Celeron J4125, 2GB non-ECC, no transcoding section
• Synology DSM 7.3 announcement, 8 Oct 2025 — third-party drive reversal and the surviving M.2 HCL footnote
• AOOSTAR WTR PRO 5825U product page — barebone price, DDR4-3200 memory support, package contents
• Unraid pricing — the one-time licence tiers, device caps and update terms
• EIA Electric Power Monthly, Table 5.3 — 18.44 cents/kWh, May 2026 US residential average

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