Ask 3 home lab enthusiasts where to start your home lab, and you'll likely get three different answers. It could be a Raspberry Pi, a cheap N100 mini PC, or a used enterprise box off of eBay. All of those things are small, quiet, sip power, and are relatively low cost as an entry into self-hosting, but in my opinion, they're not the best place to start. For your first home lab, the better machine is probably already sitting in your closet. An old ATX tower is one of the best beginner home labs money can buy, and it's often overlooked as a starting point.

A full tower can grow with you

ATX gives you a lot more routes for upgrading and evolving

A home lab doesn't truly start until you're ten containers deep with things that you're not actually using, but just experimenting with. You start with one container and end up with a bunch, and the question that actually matters is whether your hardware can absorb that growth without a re-buy. A full-size ATX machine answers that better than anything else at the price, and it's where smaller machines can't really match up. Open PCIe slots mean you can drop in a host bus adapter for more drives, a 10GbE NIC, or a GPU for hardware transcoding and the inevitable local-AI tinkering. Most of those are things a Pi or most mini PCs won't accept without serious modification. Physical drive bays and a handful of SATA ports let you build a genuine ZFS or TrueNAS pool instead of dangling USB disks off a single-board computer and praying. I've done both, and I'll tell you firsthand that the former is preferable to the latter. DIMM slots let you climb to 64GB or 128GB of RAM as your VM and container count creeps up, where soldered memory on an SBC or budget mini PC caps you early and permanently. And finally, a real ATX power supply has the headroom to actually run all of it.

The performance also falls in line similarly. If it's a repurposed gaming rig (even one that is a decade old), it has a multi-core processor and a decent chunk of memory, so it'll be able to juggle several VMs and containers easily. If it's a new machine you're putting together using pre-owned ATX parts, they're likely very inexpensive and come bundled; CPU, RAM, and motherboard combos are very common on eBay and other third-party marketplaces.

x86 is the most documented platform on earth

For a beginner, that's a blessing

A newcomer's scarcest resource isn't money or rack space, but knowledge. It's the ability to troubleshoot when something breaks, and any home lab enthusiast knows that stuff breaks all the time. This is one of the best arguments for going with a familiar form factor like ATX. It runs the usual self-hosting stack natively, with no asterisks. Operating systems like Proxmox, TrueNAS Scale, or even plain Linux like Ubuntu Server were all built and tested first on x86. There's no waiting on an ARM build, and no "works on amd64 only" surprise halfway through a tutorial. The documentation in general is also much better, because it's almost guaranteed that someone out there has had your specific issue, making it much easier to diagnose and fix.

Plenty of Docker images and smaller projects ship x86 builds and treat ARM as an afterthought, or skip it entirely. On a desktop, when something doesn't work, it's almost always user error, not a half-baked implementation. If you're new to self-hosting and home labbing, you'll come to learn that user error is one of the best modes of error, because it means you can easily fix it.

SBCs and mini PCs have a few very real advantages

Power, heat, noise, and physical footprint

A full ATX tower running 24/7 is a genuinely hungry machine, in more ways than one. In terms of power consumption, a Raspberry Pi 5 idles at roughly 3 to 4 watts; an N100 mini PC around 8 watts. A repurposed gaming desktop, depending on its age and what's installed, can idle anywhere from 50 watts to well past 100. That's not insignificant if you're running something 24/7.

The heat and noise footprint is also very significant. Low-power devices like SBCs and mini PCs typically have less robust cooling solutions because they simply require less cooling capacity, and that generally means they're quieter as well. A tower is louder than a fanless mini PC, it dumps more heat into whatever room it lives in, and it's a big box that has to physically go somewhere, which can be a drag if you're in an apartment or condo.

The full-size PC is the on-ramp

It's just part of the journey

Right-sizing your hardware requires knowing your workload, and you cannot know your workload until you've actually run things for a while. The ATX tower is the cheap, low-friction way to discover what you actually need to buy. You spend a couple of months learning what you actually run, how much storage and RAM it really takes, and whether you actually care about all of this self-hosting stuff.

The power gap, while real, is also easy to overstate for a beginner specifically. A lot of first-timers aren't truly running 24/7 yet, either. They're tinkering on evenings and weekends, and turning the lab off most of the time. And a modern-ish build with C-states and power management actually enabled idles a good deal lower than the worst-case figure suggests. It still loses to a Pi or mini PC, and I won't pretend otherwise, but it's still preferable in a lot of ways.

A full-size rig gives you a great foundation

By all means, buy the mini PC and Raspberry Pi, but just don't make it the first thing you install Proxmox on. Let the old tower be the place you make your beginner mistakes cheaply and learn what a home lab actually demands of its hardware. When you eventually move to something small and efficient, you'll be choosing it deliberately for a few specific tasks instead of the genesis of your entire setup.