Quick Summary (TL;DR): For a DIY NASAliExpress price with four to eight 3.5-inch drives, a quality ATX or SFX power supplyAliExpress price is usually the safest and easiest option: it provides the correct motherboard rails, established protection circuitry and enough native SATA power connections. Choose ATX when the case accepts it and you want the broadest choice of sensible 450–650 W units; choose SFX when the enclosure demands it, even if the available wattage is higher than your actual load. External DC plus a DC–DC converter can suit a compact one- or two-drive server, but the external brick, 12 V input, 5 V rail, connector current and simultaneous HDD spin-up all need separate checks. A PSU rated at 750 W does not consume 750 W continuously. For a server that idles at 25–60 W, measured low-load AC efficiency matters more than an impressive maximum wattage or an 80 PLUS badge alone. Our practical default: use a reputable, properly sized ATX/SFX PSUAliExpress price with native SATA cabling for a multi-bay NASAliExpress price; reserve DC solutions for builds whose entire electrical design you can verify. This is a specification- and engineering-based buying guide, not a hands-on PSU comparison.
ATX vs SFX vs External DC: Which Power Supply Should You Choose?
A home server may spend 95% of its life serving files, recording a few cameras or waiting for a Home Assistant event. The average processor load can be tiny. Yet its power supplyAliExpress price must cope with a cold boot, every disk starting, a scrub or rebuild, and perhaps a sudden CPU boost. The best unit is not necessarily the smallest, highest-rated or most expensive: it is the one that fits the case, feeds every rail and connector safely, and remains efficient at the actual 24/7 load.
| Build | First choice | Why | Main check before buying |
|---|---|---|---|
| One or two SSDs, low-power embedded motherboard | Supported direct-DC input or correctly specified DC–DC solution | Compact, potentially silent | Input voltage, connector polarity, brick quality and total conversion losses |
| Two 3.5-inch HDDs, low-power mini-ITX board | Quality ATX/SFX; DC–DC only after rail calculations | Simple cabling and dependable start-up | 12 V spin-up current and 5 V disk electronics |
| Four to six HDDs in an ATX-compatible case | Reputable 450–650 W ATX unit | Easy fit, native SATA power and expansion | Cable count, PSU depth, low-load test results |
| Five HDDs in Jonsbo N2 | SFX PSU | The N2 is specified for SFX supplies | Physical depth and cable routing |
| Eight HDDs in Jonsbo N3 | SFX PSU | The N3 requires SFX with a particularly tight depth limit | Manufacturer’s 105 mm maximum PSU length |
| Proxmox server with a GPU or other power-hungry PCIe cards | Appropriate ATX/SFX with measured peak headroom | 12 V capacity and expansion matter | Exact GPU transients, EPS and PCIe connectors |
The wattage ranges above are starting points for shopping, not a substitute for calculating the particular build. A modest NAS might operate happily on a far smaller supply, while a workstation-style server could need substantially more.
The Three Architectures Explained
ATX: The straightforward choice when the case has room
A conventional internal ATX PSU accepts mains power and provides regulated +12 V, +5 V, +3.3 V and standby outputs through standard motherboard and peripheral connections. It includes the logic required for a normal PC power button, power-good signalling and shutdown. In a NAS case with an ATX mounting position, it is usually the least complicated path.
A mainstream ATX unit typically has a larger cooling fan than an SFX unit, and the market includes many relatively modest wattages. You can choose a good 550 W model without buying a 1,000 W gaming PSU. ATX does not automatically mean quiet or efficient: the exact platform, fan curve, quality of components and independent test results matter.
An ATX unit’s length matters as much as its mounting pattern. For example, the Fractal Design Node 304 specification states ATX PSU support up to 160 mm; drive brackets, modular plugs and cable bend radius can still reduce usable clearance. Do not buy solely from the label ‘ATX compatible’.
SFX: Smaller housing, largely the same electrical job
SFX is a compact PSU form factor, not a promise of lower electricity consumption. A modern SFX unit can offer standard 24-pin ATX, EPS CPU, SATA and PCIe power through shorter, compact cables. It is attractive for cases where a full ATX housing simply will not fit.
The Jonsbo N2 specifies SFX up to 150 mm; the Jonsbo N3 specifies SFX up to 105 mm. Those are different constraints. A longer SFX-L design or an unusually deep power supply may be unsuitable for the N3 even though its mounting holes look familiar. Always consult the current case manual and check the exact PSU dimensions.
A concrete current SFX example is the Corsair SF750 (2024, UK SKU CP-9020284-UK). Corsair documents 750 W continuous output, ATX 3.1 compliance, 80 PLUS Platinum, a 92 mm fan, a seven-year warranty and eight SATA power connectors across two supplied cables. It is an example of a well-documented compact platform, not a claim that a four-drive NAS needs 750 W. Check the regional SKU and cable kit rather than assuming every SF750 revision is identical.
External DC: Two power-conversion stages, not magic efficiency
An external DC arrangement has at least two components: an AC-to-DC brick, and a motherboard or DC–DC board that produces the rails the computer needs. A motherboard with a supported 12 V or 19 V DC input may incorporate the second stage. A normal 24-pin ATX motherboard needs a compatible converter, such as a picoPSU-type unit, plus the right brick and wiring.
The Mini-Box picoPSU-160-XT is specified for a regulated 12 V input, 160 W continuous and 200 W peak. Its compact plug-in board is useful in low-power projects. Crucially, its 160 W label is not a guarantee that any random 12 V brick or SATA harness can power 160 W of drives: each output rail and cable has its own limit. The manufacturer documentation lists 5 V and 3.3 V maximum currents separately and calls for derating under poor ventilation.
Do not confuse this architecture with an all-in-one fanless AC PSU. The HDPLEX 250 W GaN AIO takes mains directly and provides ATX outputs; it is a compact internal AC PSU, not a 12 V brick plus picoPSU. HDPLEX lists 250 W, a 170 × 55 × 25 mm housing and passive cooling. Its unusual mounting and connector arrangement demand deliberate mechanical and electrical integration.
The Compatibility Checklist That Prevents Expensive Mistakes
| Item | What to verify | Why it matters |
|---|---|---|
| Case | ATX, SFX or SFX-L; depth; cable clearance; ventilation | Correct mounting pattern alone does not guarantee fit |
| Motherboard | 24-pin ATX or direct DC; EPS 4/8-pin; special 12 V-only designs | Not all boards accept the same input |
| +12 V | CPU, motors, fans, HBA and other devices; start-up demand | Multiple HDDs can start simultaneously |
| +5 V | HDD/SSD electronics, some USB and peripheral loads | A converter’s 5 V limit can be the real bottleneck |
| +3.3 V | Motherboard and any devices requiring this rail | Do not assume all DC boards generate sufficient current |
| SATA power | Native plug count, cable length, connector orientation, backplane input | Eight drive bays do not mean the PSU includes eight usable connectors |
| Standby/control | 5VSB, PS_ON#, PWR_OK and motherboard support | Necessary for predictable power-on and power-loss recovery |
| Protection | OCP, OVP, UVP, OPP, SCP and thermal protection | A supply should fail safely rather than overheat wiring |
| Region | Mains input range, approved power lead, warranty territory | US/UK/EU bundles and returns may differ |
| UPS | Total wall consumption and communication for safe shutdown | A UPS should cover both running load and orderly shutdown |
Never use a modular PSU cable from another model merely because its PSU-end plug fits. The equipment-end connectors may be standardised, but modular PSU-side pinouts are not universal. Mixing cables can place 12 V on a 5 V pin and destroy drives. Use only cables approved for the exact PSU family and revision. Likewise, do not use a CPU EPS cable as a GPU PCIe cable.
For multi-bay backplanes, check whether they take SATA power, Molex peripheral power, a proprietary loom or multiple connectors. A single socket feeding eight drives does not mean that a cheap adapter lead is suitable for the combined start-up current. Inspect the backplane manual for its input requirements and whether it provides staggered spin-up control.
HDD Spin-Up Is the Trap in Low-Wattage NAS Builds
A hard disk consumes much more current while accelerating its spindle than it may draw during idle operation. The right way to size a disk power system is to consult the maximum start current in the exact drive’s product manual, not multiply its advertised idle watts by the number of bays.
For illustration, the Seagate Exos X24 product manual contains separate 5 V and 12 V start-up requirements that vary by model and operating mode. The 10/12 TB table, for example, reports a 12 V peak DC start current of approximately 2.1 A. That is roughly 25 W on the 12 V rail per drive at that instant, before adding the 5 V component. This is a worked illustration from a specific drive-family table, not a universal specification for every Exos or NAS HDD.
Consider a hypothetical six-disk server. If the chosen drives each require 2.1 A at 12 V during spin-up, the motors alone could demand 6 × 2.1 A = 12.6 A, or 151.2 W at 12 V. The motherboard, CPU, fans, controller and 5 V electronics still need power. A nominal 160 W DC–DC board is therefore an obvious risk even if the whole NAS idles at 40 W. The actual requirement may be higher or lower: check the specific drives and whether the controller genuinely staggers start-up.
| Drive count | Illustrative 12 V motor current at 2.1 A/drive | Illustrative 12 V motor power | What this does not include |
|---|---|---|---|
| 2 | 4.2 A | 50.4 W | Drive 5 V, CPU, board, fans, converters |
| 4 | 8.4 A | 100.8 W | Drive 5 V, CPU, board, fans, converters |
| 6 | 12.6 A | 151.2 W | Drive 5 V, CPU, board, fans, converters |
| 8 | 16.8 A | 201.6 W | Drive 5 V, CPU, board, fans, converters |
The table is illustrative arithmetic, not a measured result or PSU recommendation. It deliberately assumes simultaneous starts. Staggered spin-up can reduce the peak but is not guaranteed by every motherboard, SATA controller, HBA, backplane or firmware configuration. Never base safety margins on a feature you have not verified on your own hardware.
A practical sizing method
- List the CPU, motherboard, RAM, HBA, NICs, fans, NVMe devices and every hard disk. Record manufacturer maximum electrical demands where available.
- For disks, separate 12 V spin-up current from steady-state running power and account for the 5 V rail.
- Estimate a credible simultaneous peak for the whole system. Include CPU boost and any add-in cards that may be active at boot or during rebuilds.
- Compare the result against the PSU’s continuous output on each rail, the 5 V/3.3 V combined limit and the connector/harness ratings. The large number on the box is not enough.
- Leave engineering headroom for temperature, capacitor ageing, drive replacement and expansion. Avoid relying on short-duration peak ratings.
- Verify cold boot, power-loss recovery and storage scrubs under a supported test plan, with backups already available.
For more on controllers and direct disk access, read our HBA vs PCIe SATA Card vs Motherboard Ports guide.
Why 80 PLUS Gold Does Not Tell You Your NAS Idle Consumption
A 24/7 NAS is often lightly loaded. Suppose a system needs 40 W of DC output at idle. On a 750 W PSU, that is only 5.3% of rated capacity. Most familiar 80 PLUS Gold and Platinum efficiency requirements for non-redundant desktop PSUs are defined at higher percentages. The official 80 PLUS ratings explanation lists 20%, 50% and 100% test points for those tiers; Titanium includes a 10% point, and newer Ruby criteria include 5%. Testing schemes and voltage categories differ, so check the certificate rather than treating the badge as a complete efficiency curve.
A Gold PSU can be efficient at a 250 W gaming load and comparatively inefficient at a 25 W NAS idle. Conversely, a quality larger unit may still perform well at low load. You cannot determine the winner from the wattage label alone. Look for a credible independent test reporting 10 W, 20 W or 2–10% load efficiency at your local mains voltage. Cybenetics’ PSU evaluations include much more detailed efficiency, noise and standby measurements for tested models; use the actual report for the precise revision, not a brand-wide assumption.
| DC output needed | Rated 250 W PSU load | Rated 550 W PSU load | Rated 750 W PSU load |
|---|---|---|---|
| 25 W | 10.0% | 4.5% | 3.3% |
| 40 W | 16.0% | 7.3% | 5.3% |
| 80 W | 32.0% | 14.5% | 10.7% |
| 150 W | 60.0% | 27.3% | 20.0% |
These percentages show where to read an efficiency curve. They are not efficiency percentages. Also remember that a DC–DC system has losses in both the brick and converter. An advertised ‘95% efficient DC board’ is not a claim of 95% wall-to-motherboard efficiency.
Worked wall-power comparison: identical server, different conversion efficiency
Assume, for illustration only, that the components draw a constant 40 W DC and two candidate power systems achieve 78% and 88% efficiency at that exact load. Neither percentage is attributed to a named product; real values must come from tests or measurement.
| Calculation | 78% system | 88% system |
|---|---|---|
| Wall input = 40 W ÷ efficiency | 51.28 W | 45.45 W |
| Annual electricity = W × 8,760 ÷ 1,000 | 449.2 kWh | 398.2 kWh |
| Annual cost at an illustrative £0.25/kWh | £112.30 | £99.55 |
| Five-year energy cost, unchanged tariff/load | £561.50 | £497.75 |
The difference is about £12.75 per year and £63.75 over five years in this deliberately simplified scenario. It would not justify paying £100 extra for a PSU solely for electricity savings. If the better unit is also quieter, has better protection or avoids a dangerous adapter, those are separate benefits. Your own electricity tariff, actual duty cycle and AC measurements will produce different numbers.
A further example: at 40 W DC, a 92%-efficient brick followed by a 94%-efficient DC–DC board would have a combined idealised efficiency of 0.92 × 0.94 = 86.48% and use about 46.25 W at the wall. The stages are hypothetical; efficiency varies with load and temperature. Measure the complete chain rather than comparing the DC board alone against a conventional ATX supply.
For a reusable measurement method and tariff worksheet, see NAS and Home-Server Electricity Costs.
Concrete PSU Examples Worth Comparing
These examples illustrate the types of supply, not a ranking derived from hands-on testing. Check current stock, exact SKU, included cabling and independent low-load test results before buying.
| Example | Architecture | Manufacturer-documented details | Suitable scenario | Main caveat |
|---|---|---|---|---|
| be quiet! Pure Power 12 M 550 W | ATX AC | ATX 3.0, 80 PLUS Gold, modular cables, 120 mm fan | ATX-compatible four-to-six-drive NAS with expansion | Verify SATA cable layout and PSU depth for the case |
| Corsair SF750 (2024) | SFX AC | ATX 3.1, 80 PLUS Platinum, eight SATA plugs supplied, 92 mm fan | Compact SFX-only NAS, especially if more connectors/headroom are needed | 750 W is much more than most idle NAS loads; evaluate low-load losses |
| Mini-Box picoPSU-160-XT | 12 V DC–DC; brick sold/selected separately | 160 W continuous, 200 W peak, regulated 12 V input | Carefully calculated low-power mini-ITX/SSD server | Brick, rail and wiring limits; generally not our choice for many HDDs |
| HDPLEX 250 W GaN AIO | Compact fanless mains AC ATX-output supply | 250 W, passive cooling, 170 × 55 × 25 mm | Custom fanless chassis with verified mounting and wiring | Not a drop-in SFX or conventional ATX housing; heat dissipation matters |
The be quiet! Pure Power 12 M 550 W is a useful reference for a moderate-wattage ATX platform. It is not the only reasonable ATX choice, and its 80 PLUS rating does not establish how it performs at a 30 W wall load. Some regional shops now carry other Pure Power 12 revisions; check the exact model suffix and specification sheet.
The Corsair SF750 is attractive where the enclosure requires SFX and you want a clearly documented native SATA loom. It is not sensible to pay for unused GPU cables or wattage unless fit, quality, availability and lifetime cost justify it. Its supplied cables are Type 5; do not replace them with an older Corsair Type 4 or an unrelated modular set.
The picoPSU-160-XT and HDPLEX 250 W are specialised options. The former needs a correctly specified external 12 V supply; the latter accepts mains and requires safe chassis integration. Neither should be bought on the assumption that fanless automatically means more efficient or more reliable.
The Real Cost of a Complete Power System
A PSU is only one part of a usable NAS. For a buying decision, compare the whole build, including storage and power protection, not a headline PSU price. The following table is a shopping checklist; no retailer prices or affiliate returns are assumed.
| Cost line | ATX/SFX NAS | External-DC NAS | How to evaluate |
|---|---|---|---|
| PSU or converter | Internal PSU | DC–DC board or direct-DC motherboard | Correct continuous output and protections |
| AC conversion | Built into PSU | External brick unless motherboard accepts mains (rare) | Brick must be included in price and efficiency |
| Power cables | Supplied approved SATA/EPS looms | Often additional SATA harness and DC lead | Count safe connectors, not adapters |
| Case/adapter | Correct ATX/SFX case or bracket | DC jack mounting and suitable enclosure | Clearance, airflow and mechanical security |
| Drives | Same intended HDD/SSD set | Same intended HDD/SSD set | Include full installed capacity and spares |
| Motherboard/RAM/SSD | Same intended compute platform | May need a board with supported DC input | Do not hide a platform change in PSU savings |
| UPS | UPS sized for measured wall load | UPS still needed; brick plugs into it | Shutdown signalling and runtime |
| Running cost | Measure complete AC input | Measure brick + converter + system | Five-year kWh using local tariff |
| Replacement risk | Standard internal PSU can be easy to replace | Matching brick/converter may be specialised | Availability, warranty, downtime |
A break-even calculation you can reuse
Suppose the all-in purchase cost of Option A is £85 and Option B is £135, with identical other components. If Option B saves 5 W at the wall continuously, its annual saving at an illustrative £0.25/kWh is 0.005 kW × 8,760 h × £0.25 = £10.95. The £50 premium takes approximately 4.6 years to recover through electricity alone, ignoring discounting, maintenance and tariff changes.
At a 2 W saving, the same premium takes around 11.4 years. At a 10 W saving, about 2.3 years. None of these are PSU test results. They show why a £50–£100 price difference can outweigh small efficiency improvements in a lightly loaded home server.
| Verified wall-power saving | Saving/year at illustrative £0.25/kWh | Five-year saving | Payback of a £50 premium |
|---|---|---|---|
| 2 W | £4.38 | £21.90 | 11.4 years |
| 5 W | £10.95 | £54.75 | 4.6 years |
| 10 W | £21.90 | £109.50 | 2.3 years |
If the DC build forces you to purchase a different motherboard, a custom enclosure, a special 12 V brick and extra connectors, include every one of those costs. Equally, if you already own a suitable certified brick and a direct-DC motherboard, the economics can favour DC. Compare actual components, not a theoretical ‘DC is cheaper’ claim.
How to Measure PSU Efficiency in Your Own Home Server
For a useful comparison, keep the motherboard, disks, operating system, power settings and workloads unchanged. Measure whole-system wall power using a suitably rated, accurate AC energy meter. An inexpensive smart plug may be good enough for trend tracking but can be inaccurate at very low loads; verify its specification and, where possible, cross-check it against a trusted meter.
- Record the model, firmware, drive count, power-management settings, mains voltage and room temperature.
- Measure wall watts at steady idle after services settle; note whether disks are spinning, sleeping or performing background work.
- Measure a representative active workload: file transfer, media transcode or a storage scrub. Record sustained rather than one-second peak values.
- Observe cold boot with a meter capable of capturing transients, but do not assume an ordinary smart plug captures millisecond start-up current. Use manufacturer electrical data for PSU sizing.
- Run the same workload for each configuration and record kWh over 24 hours or longer. Background updates, indexing and disk sleep can distort short comparisons.
- Compare noise, PSU temperature and UPS behaviour as well as watts. A 1 W advantage is not valuable if the replacement cannot start all disks reliably.
Software power reports (CPU package watts, drive SMART estimates or a UPS load percentage) are not a substitute for AC input measurement. CPU package power omits much of the motherboard, drives and conversion loss. UPS displays may be too coarse for a 30 W server.
For automated monitoring, use a suitably certified power meter that reports energy to Home Assistant or your preferred logging system. Any mains-voltage wiring must be handled with suitable certified hardware and competent installation. Do not open a PSU to fit a sensor; the internal capacitors can remain dangerous after unplugging.
When a Fanless PSU Is Actually a Good Idea
Silence matters in a living room or bedroom, but removing a PSU fan does not remove its heat. A fanless power supply relies on its heatsink, enclosure and surrounding airflow. In a sealed NAS with six warm HDDs, the PSU and drive temperatures can rise together. The HDPLEX 250 W GaN documentation explicitly describes heat transfer through its aluminium casing. Follow the installation guidance rather than suspending it in a foam-lined box.
A conventional quality PSU with a large, slow fan may be quieter overall than a tiny passive converter whose heat forces the case fans to spin faster. Similarly, a semi-passive PSU’s ‘zero RPM’ mode may stop its fan at idle but does not guarantee silence from coil noise or disks. Consider the entire acoustic system: 3.5-inch HDD seek noise, chassis vibration, fan placement and intake restrictions often dominate.
If the NAS sits in a cupboard, pay more attention to ventilation and ambient temperature than fanless marketing. Neither a DC brick nor an internal PSU should be buried under insulation or placed where cables are crushed.
Common Build Mistakes and How to Avoid Them
Buying by watts alone
A 1,000 W unit does not make a 45 W NAS faster, and a 160 W DC board is not necessarily adequate for six drives. Calculate 12 V, 5 V and start-up requirements independently. Check low-load efficiency data rather than extrapolating from 50% load certification.
Counting SATA plugs but ignoring their wiring
Eight connectors across two manufacturer cables can be preferable to eight drives on a collection of cheap splitters. Verify each backplane’s power input and the approved harness capacity. Avoid improvised SATA-to-Molex or Molex-to-SATA arrangements, poor-quality moulded connectors and tight bends that stress contacts. The safe answer is sometimes a different PSU or an approved additional cable.
Reusing modular cables from an old PSU
Modular plugs are not a universal pinout standard. Use only exact manufacturer-approved cables. If you replace a PSU, replace its modular power cables too unless the manufacturer explicitly documents compatibility for those precise models.
Choosing the wrong external brick
A 19 V laptop adapter is not a suitable substitute for a converter specified for regulated 12 V. Check voltage, polarity, current, plug size, approvals and protection features. For example, a hypothetical 12 V/8 A brick can deliver at most 96 W nominal DC before allowing for the converter’s own losses; it cannot magically provide a 160 W continuous system budget.
Overlooking 3.3 V on SATA power
Some enterprise or shucked SATA drives may respond to the SATA power-disable feature associated with pin 3, and may not spin up when fed by certain power harnesses. Check the exact drive documentation and backplane behaviour. Do not treat electrical tape on a power connector or cutting wires as a general solution. Use a supported harness or backplane arrangement and keep warranty/safety implications in mind.
Assuming a UPS solves bad power distribution
A UPS does not fix an overloaded 5 V rail or an unsafe splitter. It protects against external power interruption when correctly sized and configured. If you need orderly shutdown, see Network UPS Tools with Home Assistant and NAS and UPS VA vs Watts.
Treating ‘ATX 3.1’ as a NAS requirement
ATX 3.0/3.1 and modern PCIe connectors matter especially for contemporary graphics-card transients and platform compatibility. They do not automatically improve NAS disk safety or low-load efficiency. A reliable older standard PSU can be perfectly suitable if it meets the motherboard and electrical requirements; a new unit still needs the right SATA cables and measured performance.
Suggested Configurations by Build Type
Low-power SSD-only Home Assistant or small Proxmox node
If your mini PC or embedded board already has a manufacturer-approved external power adapter, use that intended supply. Do not retrofit an ATX PSU merely to gain an 80 PLUS label. For a DIY motherboard with 24-pin input and one or two SSDs, a correctly specified DC–DC solution can be elegant, but calculate all rails and include the brick’s losses. For compute hardware choices, see DIY NAS Motherboards: N150 vs Core i3 vs AMD.
Four- to six-bay DIY NAS in an ATX-compatible chassis
Start by looking for a reputable moderate-wattage ATX PSU, native SATA power leads, sufficient +12 V capacity and documented protections. You generally do not need a premium gaming supply or custom DC conversion. Check fan placement so the PSU does not obstruct the HDD cooling path. A unit with strong low-load results can be worth paying for, but do the five-year payback calculation.
Five-bay Jonsbo N2
Use the enclosure’s specified SFX format. Choose an SFX PSU whose dimensions and cables fit, count drive and backplane inputs, and allow room for the CPU power lead and cooling fan. Do not assume that a ‘small’ ATX unit fits. The Mini-ITX NAS case comparison covers the case-level trade-offs.
Eight-bay Jonsbo N3
The N3’s published SFX ≤105 mm requirement should be checked against the exact PSU, including cable bend clearance. Eight drives may create substantial simultaneous start current; evaluate the backplane wiring, HBA, drive specifications and 12 V budget together. The number of SATA plugs on a retail box is not enough if the backplane has a different input arrangement.
Mixed VM, media and storage server with PCIe expansion
A larger PSU can make sense when a dedicated GPU, multiple NICs or other cards add real load. Size for sustained power and transients, not for a generic ‘server’ label. For the compute side, see Best Mini PCs for Proxmox and Multiple Virtual Machines and N100 vs N150 vs Core i5 vs Ryzen.
Frequently Asked Questions
Is SFX less efficient than ATX?
Not inherently. SFX specifies a smaller physical format. Actual efficiency depends on the PSU design, rating, operating load and input voltage. Compare independently tested efficiency curves for the specific models, particularly at the 20–80 W DC loads common in small servers.
Does a 750 W power supply use 750 W all day?
No. Its rating describes available output capacity. A NAS drawing 45 W from the wall uses approximately 45 W at that moment, regardless of whether its PSU is rated at 450 W or 750 W. Different PSUs may incur different conversion losses at that load.
Can I use a 160 W picoPSU for four HDDs?
Possibly for a carefully engineered system with suitable disks, controlled start-up and adequate rails, but do not assume so. Four HDD motors alone can impose a significant 12 V surge. The external brick, converter, 5 V rail and SATA harness all require independent checks. For a typical four-bay NAS, a conventional quality ATX/SFX PSU is simpler and generally preferable.
Is 80 PLUS Platinum worth paying extra for?
Sometimes, but not automatically. A small NAS can operate below the load points covered by most 80 PLUS tiers. Compare low-load results and calculate the annual kWh saving. A £50 premium for a 2 W saving at £0.25/kWh takes over eleven years to recover through electricity alone.
Do NAS hard drives use 12 V or 5 V?
Most standard 3.5-inch SATA HDDs use both rails: 12 V primarily for the motor and 5 V for electronics. Exact current requirements depend on the model and operating state. Consult the drive’s power table rather than using a generic watts-per-disk estimate.
Can a 12 V-only motherboard run from a laptop charger?
Only if the manufacturer explicitly supports the adapter’s voltage, polarity, connector and current capacity. A common 19 V laptop charger is unsuitable for a board that requires 12 V. Do not improvise mains or DC wiring.
Should I choose a fanless PSU for a quiet NAS?
Only when the chassis can dissipate its heat safely. Fanless power conversion may be silent, but HDDs, fans and vibration can dominate noise. A well-ventilated conventional PSU with a slow fan is often the simpler solution.
How much PSU headroom should I leave?
Enough for the measured or documented simultaneous peak, rail-specific loads, component ageing and intended upgrades. There is no universal safe percentage that replaces an electrical budget. In particular, size for HDD spin-up and any GPU transients, not just idle power.
Verdict: Buy for Electrical Fit First, Then Low-Load Efficiency
For most four- to eight-drive DIY NAS builds, ATX or SFX wins on practicality. Use ATX if the case accepts it; use SFX when space demands it. Look for an established model with adequate native SATA power wiring, appropriate protections, reliable warranty support and credible low-load test data. A 550 W ATX model can be a better purchase for a quiet, lightly loaded NAS than a premium 850 W model with no measured advantage at idle.
Choose external DC when the hardware was designed for it or when you can validate the entire brick-to-board-to-drive electrical chain. It is especially appealing for low-power SSD-only systems, not as a shortcut for a large HDD array. Do not buy a PSU purely on 80 PLUS tier, a fanless claim or the largest wattage figure. The objective is reliable starts, stable rails, safe cabling and modest real-world electricity use over years of operation.
Related NAS and Home-Server Guides
- NAS and Home-Server Electricity Costs: Choosing Efficient Hardware
- DIY NAS Motherboards: Intel N150 vs Core i3 vs AMD Platforms
- Best Mini-ITX Cases for a 4- to 8-Drive NAS
- HBA vs PCIe SATA Card vs Motherboard Ports
- Best UPS for Home Assistant, Router and NAS
Manufacturer Specifications and Independent References
- 80 PLUS — Official efficiency rating and test-load definitions
- Cybenetics — Corsair SF750 Platinum ATX 3.1 evaluation
- Corsair — SF750 2024 UK model and cable specification
- be quiet! — Pure Power 12 M 550 W specification
- Mini-Box — picoPSU-160-XT specification
- Mini-Box Europe — picoPSU-160-XT electrical manual
- HDPLEX — 250 W GaN fanless AIO specification
- Seagate — Exos X24 product manual and drive power tables
- Jonsbo — N2 case specifications
- Jonsbo — N3 case specifications
- Fractal Design — Node 304 installation manual
Source review: 10 October 2026. Manufacturer product revisions, warranty terms, regional availability and specifications can change. No PSU was physically tested for this article; hypothetical electricity calculations are labelled and should be replaced with measurements for a particular build.