Seasonic G360 PSU: High efficiency & performance, low price

The 360W power rating and the modest price tag make it seem like a throwback to Pentium 3 days but the G360 is a modern PSU in every other way, with a direct lineage to Seasonic’s vaunted X-series. FLASH: Seasonic USA is giving away G360s to two lucky SPCR forum members!

Only two quarters ago in February 2012, I remarked in a review of the Seasonic
350TGM that "if you want a quality power supply built into a modern, compact
PC, the 200~400W area is pretty barren." Manufacturers seem to have seen
the same light, because in recent months, there has been a small upsurge of
new, modest power, high efficiency ATX power supply introductions. Aside from
the fanless and pricey Seasonic X-400 80 PLUS Gold, there had been virtually
no consumer PSUs offered at this power range. Now, there’s the AURUM
GOLD 400 from FSP, the Magna
Platinum 400 from Sparkle Power, the
Golden Green 80 PLUS Gold 350P14XE from Super Flower, and most recently,
the Seasonic
G360 80 PLUS Gold. We are gathering up samples of the rest, but the hottest
item for PC silencers is the Seasonic: The company has been the
pioneer in low noise and high efficiency power supplies, and they’ve
been the most consistently recommended PSUs at SPCR for over a decade.

Everthing comes and goes… and comes around again! When I first started reviewing
computer power supplies a decade ago, a 300W PSU was considered quite powerful,
and 400W was about as high as the ratings went. Then came 130W CPUs and multiple
200W video cards for gamers, and kilowatt PSUs. For a while, it was hard to
find any retail packaged PSUs rated for less than 450~500W, and 600W seemed
to be the new norm.

The good news is that the power race over the past decade was not for naught.
It was accompanied by dramatic increases in power supply efficiency from well
below 70% at the start of the period to over 90% today (virtually mandated for
effective cooling of PSUs approaching kilowatt rating), a steady decline in
CPU power demand as Intel (and AMD, to a less successful degree) got seriously
focused on energy efficiency, and most recently, significant improvements both
integrated graphics performance and the power draw of high performance discrete
graphics as well. As a result, the typical power requirements of modern desktop
PCs are about as low again as during the era of Pentium 3, when 250~300W PSUs
were the norm. It is in the context of these trends in PC component technology
that we can fully appreciate the introduction of the Seasonic G360.

New carton is bright and cheerful, the G360 is retro-small with sleeved non-detachable cables, and well protected in a close-cell foam.

Seasonic says the G-series are a response to customer calls for high efficiency
PSUs like the X-series in a lower power range, with fewer bells and whistles,
and lower pricing. The G360 is the lowest power model of the G series, first
shown at Computex Taipei in June. It differs from the 450W, 550W and 650W models
in being smaller— 14 cm deep compared to 16 cm — and not having any
detachable cables. All the G models have 80 PLUS Gold efficiency (peak >90%),
which begs the question of whether they might hijack sales from the X-series,
also rated Gold. There are several differentiators between them, though, with
the X-series clearly positioned as the more premier series.

• X-series cables are all detachable; the G360 is non-modular, and the other
  G-series models are described as "semi-modular", which probably
  means the main ATX12V and other always used cables are not detachable.
• An ADDA fan is used in the G-series, rather than the sophisticated custom-specified
  Sanyo-Denki fan in the X-series.
• The controller in the X-series keep the fan from spinning up until around
  ~50% load is reached, making them semi-passively cooled; the G-series fans
  are fully active and spin up at turn on, although at very low speed.
• The capacitors in the G-series are not exclusively Japanese parts, though
  many critical ones are.

First and foremost, the Seasonic 360G is 80 PLUS Gold certified. This is about
the lowest power Gold rated ATX PSU. The official
80 PLUS test report (PDF) cites a peak of 90.7% efficiency at half power,
and 88.3% at 20% load (74W). It is at the <200W loads where typical modern
desktop PCs operate, and maximizing PSU efficiency is good for both heat and
noise.

DETAILS

The G360 is impeccably finished in a slightly reflective flat black paint.
Hexagonal pattern grills are used for both intake and exhaust vents. Interestingly,
the grill over the fan is part of the casing, like in the X-series. The casing
is a classic clamshell, and as with all Seasonic PSUs in recent memory, the
fit is superb; the two halves fit perfectly together with no play or give. Such
attention to detail is unusual and a pleasure to behold.

INSIDE THE G360

As mentioned earlier, the casing is fitted to a high tolerance, and it was
a bit of a struggle to get the two halves apart. Once open, the familiar ADD
fan from pre-X series Seasonic PSUs is visible, and puny heatsinks reminicent
of the ones that appeared in old 250W PSUs. Those heatsinks are where the similarity
to earlier PSUs end; the rest of the components in the PSUs are not dissimilar
to what’s found in the X-series, with three daughter boards increasing both
parts count and density.

OUTPUT CABLES

The output cables are long enough for most cases, even with bottom PSU placement,
which puts the main ATX and AUX12V connectors on the motherboard farther away.
There is only one graphics card power connector, which is appropriate for the
G360’s power rating.

1 – Main ATX 20/24-pin connector, 20” (51cm)
1 – 4-pin AUX12V connectors that combine into an 8-pin EPS12V connector, 22”
(55cm)
1 – 6-pin connector for video card, 22 ” (56cm)
1 – two SATA power connectors, 25” (63cm)
1 – two SATA power connectors, 20” (51cm)
1 – three 4-pin Molex, 26” (66cm)
1 – adapter cable for 4-pin Molex to 2 floppy drive power connectors, 6"
(15cm)

TESTING

For a fuller understanding of ATX power supplies, please read
the reference article Power
Supply Fundamentals. Those who seek source materials
can find Intel’s various PSU design guides at Form
Factors.

SPCR’s
PSU Test Platform V4.1. is the basic setup for the testing. It is a close simulation of
a moderate airflow mid-tower PC optimized for low noise. There is one major change: The primary testing is done with the PSU NOT inside the hotbox but atop it, out of the heat path. This is in recognition of several realities that prevail today:

• In SPCR’s earlier test platforms, the internal temperature varied proportionately
  with output load. The tested PSU was subject to this heat, and operating ambient
  temperature rose with increased load, reaching >40°C and often much
  higher at full power. This was a realistic simulation of a mid-tower PC case
  where the PSU is mounted conventionally at the top back portion of the case.
• The vast majority of "serious" PC cases for the home builder place no longer position the PSU at the top back corner. They put the PSU at the bottom/back corner, mostly out of the path of heat from the other components in the case. This design concept took root with the Antec P180 going back over 5 years, and dominates the DIY case arena. This means the PSU generally has to dissipate only its own heat.

Now, we’ve reversed our approach: The PSU is tested briefly in
the hotbox only to check what happens to noise, fan speed and temperatures when
it is used in an outmoded case design.

Acoustic measurements are performed in our own anechoic chamber with ambient level of 11 dBA or lower, with a PC-based spectrum analyzer comprised of SpectraPLUS software with ACO Pacific microphone and M-Audio digital audio interfaces.

REAL SYSTEM POWER NEEDS: While we test the PSU to full
output in order to verify the manufacturer’s claims, real desktop PCs simply
do not require anywhere near this level of power. The most pertinent range of
DC output power is between about 40W and 300W, because it is the power range
where most systems will be working most of the time. It is true that very elaborate
systems with the most power hungry dual video cards today might draw as much
as another 150~300W, but the total usually remains under 600W.

TEST RESULTS

The ambient temperature was 23~24°, and the ambient noise
level was ~10.5 dBA.

1. EFFICIENCY — This is a measure of AC-to-DC
conversion efficiency. The ATX12V Power Supply Design Guide recommends 80% efficiency
or better at all output power loads. 80% efficiency means that to deliver 80W
DC output, a PSU draws 100W AC input, and 20W is lost as heat within the PSU.
Higher efficiency is preferred for reduced energy consumption and cooler operation.
It allows reduced cooling airflow, which translates to lower noise. The 80 Plus
Gold standard requires 87% efficiency at 20% load, 90% efficiency at 50% of
rated load, and 87% at full rated load.

At the super low 20W load, efficiency was pretty good at just
under 70%. Efficiency rose quickly as the load was increased. 90% efficiency
was reached around the 100W mark, broke 91% by 150W, reached a peak of 92.2%
at 200W, then slid a bit to 89.4% at full power. These exceed 80 Plus Gold requirements,
especially at the higher loads.

Note that in the crossload test, the loading exceeded the rated
power by 12W. No signs of stress or strain were noticed in voltage regulation
or ripple & noise. However, adding even a half amp more to the 12VDC line triggered
the overload protection, which promptly shut the PSU down. After reducing the
load, the PSU restarted without any issues. This suggests a cautious approach
to ensuring that the PSU is not subject to overload.

2. VOLTAGE REGULATION refers to how stable the output voltages
are under various load conditions. The ATX12V Power Supply Design Guide calls
for the +12, +5V and +3.3V lines to be maintained within ±5%.

At all load levels, the critical 12V line was 12.22V, within +0.22V
(1.9%) of 12V. It hardly changed at all throughout the load testing, ending
at 12.18V at full load. The 5V line started a touch high at 5.07V (+1.4%) and
went down to 5.03V at full load. 3.3V ranged from 3.38V to 3.32V (+2.4% to +0.6%).
These are superb results, better than voltage regulation needs to be for any
PC.

3. AC RIPPLE refers to unwanted "noise"
artifacts in the DC output of a switching power supply. It’s usually very high
in frequency (in the order of 100s of kHz). The peak-to-peak value is measured.
The ATX12V Guide allows up to 120mV (peak-to-peak) of AC ripple on the +12V
line and 50mV on the +5V and +3.3V lines. Ripple on all the lines was excellent
at all power levels, generally staying under 13mV through the lower half of
the power range. Even at maximum power, the 12V ripple stayed at just 25mV.
It’s about best we have measured… but remember that many other tested PSUs
were loaded to double and triple the maximum load of the G360.

4. POWER FACTOR is ideal when it measures 1.0. In the most
practical sense, PF is a measure of how "difficult" it is for the
electric utility to deliver the AC power into your power supply. High PF reduces
the AC current draw, which reduces stress on the electric wiring in your home
(and elsewhere up the line). It also means you can do with a smaller, cheaper
UPS backup; they are priced according to their VA (volt-ampere) rating. Power
factor was excellent for this model, as it usually is for Seasonics, running
at or close to 1.0 through most of the loads.

5. LOW LOAD TESTING revealed no problems starting at very
low loads. Our sample had no issue starting up with no load, either, and the
power draw was low. The 0.4W power draw in standby (power switch on but computer
off) is excellent.

6. LOW & 240 VAC PERFORMANCE

The power supply was set to 200W load at various AC input voltages.
Most full-range input power supplies achieve higher efficiency with higher AC
input voltage. SPCR’s lab is equipped with a 240VAC line, which was used to
check power supply efficiency for the benefit of those who live in higher mains
voltage regions. We also used a hefty variac to check the stability of the PSU
under brownout conditions where the AC line voltage drops from the 120V norm.

Efficiency improved to nearly 94% at 240VAC. The sample passed
the 100VAC minimum input at 200W load without any issues, with a 1% drop in
efficiency. Neither voltage regulation nor ripple changed appreciably during
these tests.

7. TEMPERATURE, COOLING & NOISE

The fan in the G360 started up at a very low speed, estimated
to be 600~700 RPM. The subjective noise was extremely low, basically inaudible
from a meter distance. Very close up (under 1′), a bit of electronic noise was
faintly audible, along with a slight buzzy sound, probably from the fan’s ball
bearings. There some tonal aspects, but the overall level was too low for them
to have any impact. In a ntushell, it was virtually silent.

The default ~13 dBA@1m SPL did not change till around 200W load,
when the controller started spinning the fan up a bit. After about 15 minutes
at 200W, the SPL had risen up to 19 dBA, which is still pretty quiet but clearly
audible in a quiet room. From that load up, the fan sped up quickly, hitting
24 dBA at 250W, and 34 dBA at 300W. At full load, the fan managed to speed up
just a wee bit more for a maximum of 29 dBA.

The high efficiency combined with the agressive fan speed profile
above 200W ensures that the G360 stays as cool as a cucumber: There’s little
heat to dissipate, and the increased fan speed at higher power loads disspates
what heat there is very quickly. Even at maximum load, the exhaust air temperature
was only 33°C.

IN THE HOT BOX

When exposed to the heat of the hotbox, the Seasonic G360 fan
started to spin up about 50W lower, as one could predict. The PSU’s cooling
system has to handle much more heat, and the fan controoler relies on a thermal
sensor, so naturally, it ramps up at a lower load. Hence, 150W is the point
where the fan started to speed up. Still, in the typical standard ATX mid-tower
case with modern system featuring an IGP or a <80W GPU, it would be rare
for the PSU fan to become intrusive.

COMPARISONS

The comparison table below shows the SPL versus Power Load data on PSUs tested
in ambient room temperature, typically 20~24°C. It is most relevant when PSUs
are used in cases that provide wide open access to cooler outside air for the
PSU cooling fan. Its rank is low, although ion a real system up to ~200W load,
it is hard to differentiate the PSUs on the table on the basis of noise.

The comparison table below shows the SPL versus Power Load data on all the
PSUs tested in the hotbox. It’s difficult to rank them, as the measured SPL
varies with power load. The units which are quietest at minimum load are not
always the quietest at midload (100W~300W), which may make them louder in actual
use. Then there’s the noise level at 400W and up, which will determine the quietest
PSUs for high power gaming rigs, during actual gaming. In this environment,
the G360 ranks poorly again, due to the relatively quick ramp-up of fan speed
as load increases.

Caution: Please keep in mind that
the data in the above table is specific to the conditions of our test setup.
Change the cooling configuration, the ambient temperature and any number of
other factors, and you could change the point at which the fans start speeding
up, as well as the rate of the rise in speed. The baseline SPL is accurate,
however, probably to within 1 dBA.

CONCLUSIONS

The Seasonic G360 power supply brings much of the X-series
benefits to a lower power and price range without significant sacrifices. Its
electrical performance and build quality are excellent, and the 5-year warranty
dispells doubts that component quality might have been sacrificed to achieve
the low price point.

The quick safety shutdown at only ~20W above the rated output
load suggests that Seasonic engineers are more stringent in keeping the PSU
from being operated beyond its parameters, perhaps reflecting the use of less
tolerant components. The aggressive fan control profile also suggests that Seasonic
is hedging its bets on longevity with a higher airflow than has been the norm
for many of their other PSUs at similar loads. So the G360 is not the ideal
PSU for a system that has low ventilation or airflow and sustained peak power
higher than 150~200W.

Still, the high efficiency makes very low fan noise possible at
lower loads, and if DIY users stay true to the usual practice of buying at least
double the power their systems really need, the G360 will remain very quiet
in most modern systems with a single intro or mid-range graphics card and a
case with external air feed for the PSU fan. Such cases are the norm these days.

The G360 is a kind of throwback in some ways, as very few ATX
PSUs rated for such low power have been released in recent years. But the power
rating, small size and small heatsinks are the only reminders of earlier PSUs.
This model has super high efficiency (over 90%), vanishingly low ripple and
noise, superb voltage regulation, and a default fan level that makes even Seasonic’s
earlier 300~400W models seem noisy.

The $60 sale price at Newegg and other vendors makes this little
PSU almost irresistable for SPCR aficianados. At time of writing, at least a
handful of SPCR forum regulars have shared the experiences of their recent G360
purchases. There will surely be more.

Much thanks to Seasonic
USA for the review sample… and the G360
Giveaway Draw for SPCR forum members.

For exceptional performance and value, the Seasonic G360 receives the SPCR
Editor’s Choice Award

* * *

SPCR Articles of Related Interest:
Power Supply Fundamentals

Recommended Power Supplies
SPCR PSU Test Rig V.4
Kingwin
Stryker STR-500
Seasonic X-400 Fanless
Seasonic X-650: Seasonic Hits
Gold
Seasonic SS-350TGM 80
Plus Gold TFX
Kingwin Lazer Platinum
550W Power Supply

* * *

Discuss
this article in the SPCR Forums.