Seasonic M12D SS-850W PSU

Comparative Efficiency

As we said on the previous page, the Seasonic mixes it up very much with the best of them in the top quarter of the table; it may not hit the best scores, but it's only a fraction of a percentage out in all cases bar the full load figure where it drops just 1.5 percent to the Cooler Master UCP 900W.

In fact, in high loads the Antec Signature 850W and UCP 900W both directly compare to the Seasonic M12D 850W, and other popular PSUs like the BFG ES 800W and Corsair HX1000W aren't too far behind either. It maybe revolutionary for Seasonic, but the rest of the industry already caught up last year - the Signature, for example, has been on sale for well over six months now.

The impressive factor for us was the idle efficiency (20 percent) which hits over 86 percent - that's the most we've seen to date and although admittedly our range is limited for this test factor, compared to what we've previously seen as the benchmark in the 800 to 900W power rating, Seasonic is comparatively excellent.

Conclusions and Value

After the 100 percent load fan-speed realisation I have to say we were a little disappointed because Seasonic has built this up to be the end-all PSU that it has spent years developing. I'm not going to deny the fact it contains some fantastic engineering and quality components that is rarely equalled, however in reality, it's probably over-engineered. The 20 percent efficiency is impressive but the rest are as good as what's already on the premium market.

The Sanyo Denki fan is high quality, the build and topology is quality and Seasonic drop a five year warranty and one year swap out service behind it as well. James at CustomPC recently used the same M12D to run three GeForce 9600 GSOs and a Phenom X4 for a folding rig. That's up to 400W from the graphics cards and another 150 to 175W from the motherboard underneath, making around 550W (65 percent) of consistent power draw yet it remained very cool and certainly wasn't the loudest thing in the case.

At the time of writing, Scan is currently the cheapest in the UK at £166, and Nanopoint has told us it's fighting with UK retailers (like OCUK and Novatech) selling its M12Ds at well over the RRP it recommends. With this in mind, be careful where you shop and check everywhere! If you simply can't find it for the price that's competitive, buy something else because there's enough high quality competition at this end of the PSU industry.

Having not kept up with the quite rampant price rises recently, we originally felt this was still quite expensive for an 850W PSU, however searching for the competition it seems that finding an Antec Signature 850W in the UK is pretty difficult and the only one with a stock of just two shifts for a competitive £160.99 (inc. VAT). Meanwhile the (non modular) Cooler Master UCP 900W can be bought for as little as £145.83 (inc. VAT), although the Enermax Revolution 850W is more expensive at £183.99. While we recently were mightily impressed by the 950W model, we don't feel the 850W is worth £20 more for a fraction more efficiency and a groovy coating on the externals.

The be quiet! 850W Dark Power Pro is also modular, £30 cheaper, just as efficient (we have tested it) and quieter all the way up to 100 percent load, but it runs notably hotter so both are not entirely comparable because they're suitable for different case environments.

We rate the M12D on a par with the Antec Signature - the Antec fairs a little better at full load and low efficiency, but we prefer the M12D's modular cables and connectivity. Compared to the be Enermax Revolution 85+, the M12D is a little lower in efficiency and the Enermax is even quieter still, but the M12D beats it on fan quality and aesthetics are to personal taste. Better still for noise performance is the be quiet! Dark Power Pro 850W, however its target market is different because the be quiet! requires better ventilation making it more case specific.

Final Thoughts

Overall, most of us buying an 850W unit are looking to power a hefty rig but even with two Radeon HD 4870 X2s and an overclocked Core i7 it'll only rarely peak at around 800W, and most of the time it'll sit in the nice 50 to 75 percent load range, even when gaming. At this load level, the Seasonic is very quiet, and coupled with an exceptionally high build quality, good warranty and a competitive price certainly makes for a shortlisted item.

If you're after a premium PSU, £166 is a good price to pay these days, but beware and don't accept more without checking the prices are consistent, otherwise grab an equally good Antec Signature or the be quiet! Dark Power Pro. There's a lot of competition at 850W, meaning there are far too many great products to make the M12D 850W the definitive choice, but we feel Seasonic holds its head up nicely with a very solid product we would certainly look at buying ourselves.

• Efficiency/Voltages
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• 9/10

• Noise/Heat
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• 8/10

• Features
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• 9/10

• Value
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• 7/10

• Overall
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• 9/10