It's been a while since I reviewed a Seasonic product, and figuring out and witnessing the performance Seasonic's flagship Prime Fanless model offers has been interesting. The TX-700 in many ways shines, but its overall performance failed to impress me, and the whole package doesn't look as appealing as it could because of its stiff price tag. In terms of overall performance, the TX-700 loses notably to an older sample of the Prime Titanium Fanless 600 W model I had evaluated two years ago. Two more TX-700 samples I have on hand performed similarly to the one reviewed here, with overall performance still considerably lower than the aforementioned 600 W fanless model. If it weren't for the incredible performance the Prime Titanium Fanless 600 W achieved two years ago, I wouldn't be so hard on the TX-700 since it is a fully passive unit, which means it cannot compete with actively cooled PSUs. That said, the SilverStone Nightjar 700 W beat the TX-700 I evaluated by nearly 5% in overall performance.

Overall performance aside, along with the loose load regulation on the minor rails and mediocre transient response, my biggest concern consists of the voltage drops I noticed on all rails during one of the turn-on transient tests. Such high voltage drops can cause issues, mainly during the wake-up phase of a system, which is when components will draw more power. Such big voltage drops on the rails put a lot of stress on the DC-DC converters, which can cause several issues, even failures. Another problem I noticed is the high power-on time exceeding 100 ms. To avoid compatibility issues with mainboards, most manufacturers keep the PSU's power-on time below 100 ms, ideally below 50 ms. Lastly, the lack of support for Alternative Sleep Mode is another concern since such an expensive PSU is only bought with the intention of keeping it for many years to come, which means it has to be future-proof.