NZXT H3 Flow Micro-ATX Airflow Case Review

A breath of fresh air for Micro-ATX

NZXT is one of those enclosure brands that has been around for a long time (founded in 2004), and they’ve offered a variety of enclosure types. From all metal and glass to plastic gamer aesthetics, NZXT has done it all, but often with the complaint that there wasn’t enough airflow. Their new H3 Flow, Micro ATX tower is aiming to change that perception, and at an affordable MSRP of $79.99. Let’s dig in and see how they’ve done.

Features of the H3 Flow (via NZXT):

• Space-Saving Size: A space-efficient micro-ATX chassis that accommodates high-performance components without compromise.
• High-Airflow Design: Ultra-fine steel mesh panels and a ventilated PSU shroud maximize airflow while effectively filtering out dust.
• Extensive Cooling Support: Supports up to a 280 mm radiator in the front, a 240 mm radiator on top, and up to seven fans for powerful, customizable cooling performance.
• Full-Size GPU Support: Fits graphics cards up to 377 mm (without front fans), 352 mm (with front fans), or 317 mm (with front radiator and fans installed).
• Pre-Installed Rear Fan: Includes one F120Q (CV) fan at the rear to provide efficient exhaust airflow straight out of the box. CV = Case Version (3-pin DC)
• Simplified Cable Management: Integrated cable channels and multiple tie-down points make it easy to route and organize cables for a clean, organized build.
• Back-Connect Motherboard Compatible: Ready for rear-connector motherboards like ASUS BTF and MSI Project Zero, enabling a clean, cable-free aesthetic.
• Tool-Free Access: Removable top, front, and side panels allow for easy upgrades and cleaning—no tools required.

Overview

The first thing you notice when pulling the H3 Flow out of the shipping box is that it is very small (35 litres). While that is about two times the volume of some of the more recent ITX cases I’ve reviewed, it doesn’t actually seem that much larger. The second thing you will notice is that it is also very light (4.8 kg or 10.58 freedom units). It feels about the same weight as those aforementioned ITX enclosures. Despite the diminutive size, the H3 Flow is capable of supporting up to 377mm Graphics cards (if you don’t put a radiator in the front).

After you’ve stopped marveling at those two observations, then you realize you can practically see straight through every metal panel on the case. The mesh on the H3 Flow has an extremely open pattern, which probably contributes to the light weight of the enclosure. Despite the light weight and the open mesh panels, I found that the H3 Flow was well built, with as little flex as you’d expect from the panels of an enclosure at this price point.

The H3 Flow is compatible with either Micro-ATX or Mini-ITX form factor motherboards. If you can find one, you can even use a Back-to-Front Micro-ATX motherboard. You can use a full size ATX PSU, and there is plenty of support for multiple fans, and even a couple of radiators. Unfortunately, the only included fan is a 120mm rear exhaust fan, which is of the usual quality you get in budget enclosures.

The Build

Even with the small size, the H3 Flow was really a breeze to build in. With the front and two side panels removed, it opens up nicely, allowing good access to the inside of the chassis. The rear side panel has captive thumb screws, which is a nice touch on a case in this price range, but there are no included Velcro straps for cable management. There are however, a lot of cable tie points, which allow for neat routing of your cables. One (very minor) issue I have along these lines is that the included plastic cable ties are too short.

I also wish that the bottom of the chassis were as ventilated as the rest of the case. Unfortunately, it is basically solid, forcing you to mount the power supply with the fan facing upwards. In my test system, this didn’t present a big issue, but if you were to use one of the larger and thicker GPUs on the market, the GPU and the PSU could be competing for air at that side of the chassis.

Finally, the H3 Flow uses that sliding PCI Bracket design that I detest. This design is mostly found on the lowest priced cases on the market, but it’s just terrible. I can’t imagine a standard design is even pennies more expensive to tool and manufacture, but here it is again.

That’s made up for by the greatest advancement in PC enclosure design of the last 10 years…a single connector for the front panel! Now that these are a thing, I can’t even fathom why any case manufacturer is still doing the individual connectors. If you buy an enclosure in 2025 that still uses individual connectors for the front panel, then just understand that the case designer is a sadist who wants you to suffer. Thank you NZXT for not making us go through front panel connector hell any longer.

More seriously, I have no major complaints with the build process in the H3 Flow. It was straightforward, and the design made everything quite easy. This would be a very good enclosure to start with for someone building their first PC.

Performance Testing

I know that you’re all probably sick of hearing about natural disasters, but during the rearranging of the house we’ve had to do for repairs following Helene, I have somehow misplaced my test system motherboard (which was ATX anyway and couldn’t have been used in this chassis), and the cooler. So, moving forward, I will be testing all cases on equal footing. Everything is going to be tested using the same platform used in my SFF case tests.

Specification of Test System:

• Intel Core i5-12600K CPU
• Gigabyte Aorus Z690i Ultra Lite Motherboard
• ID Cooling IS-55 Low Profile CPU cooler
• 16 GB (2x8GB) G.Skill Trident Z DDR4-3333 (@ 3600 MT/s) Memory
• PNY RTX 3080 12GB XLR8 OC – fan speed set to standard curve

All tests conducted at a controlled ambient temperature of 23.5° C. Motherboard CPU fan curve set to “Performance”, case fans set to 1000 RPM

• CPU Temperature Testing: Cinebench R23
• GPU Temperature Testing: Unigine Heaven set to Ultra Detail, Extreme Tessellation, and 8x Anti Aliasing at 1080p for 30 minutes
• Gaming Test: Performed for 30 minutes using Marvel’s Guardians of the Galaxy, 1920×1080, Ultra Settings with Ray Traced Lighting and Reflections on, DLSS set to Quality mode

Considering that this system only includes a single exhaust fan, these numbers are pretty amazing. The only real outlier in the numbers is the GPU idle. This is high for two main reasons. It is a semi passive cooler on this GPU, and there are no intake fans included with the case. Not only would a couple of 140mm fans in the front reduce the idle temp, but I would bet that you’d see lower load temps on the GPU and CPU as well.

The rear exhaust fan really should be replaced with something better quality as well. It moves a decent amount of air, but at anything over about 975 rpm, it’s quiet loud, and over 1100 it is quite obviously the loudest component in the system. Even below 975 rpm, the tone of the fan is a bit unpleasant to my ears.

Despite the fan noise, the temperatures speak for themselves. Even the best SFF cases I’ve tested can’t match the temps of the H3 Flow.

Conclusion

So, the H3 Flow is easy to build in, well built, has good thermal performance, and is $80. That’s all great. There are a few things to take into account here though. To really maximize performance, you need to add at least two fans as intake, and you will probably want to replace the rear fan. There are some good quality fans on the market now at just under $10 each, but then you’re adding $30 to the $80, which raises the question of value.

Is the H3 Flow worth this price, considering you will need to add fans? Actually, I believe it is, provided you want something small that still supports ATX PSUs and Micro-ATX motherboards. The thermal performance with the H3 Flow is really outstanding, and I’m happy to give it the PC Perspective Silver award.