A $15 Raspberry Pi Zero 2W does Pi-hole better than any spare PC you have lying around

At a glance:

• Running Pi-hole on a dedicated Raspberry Pi Zero 2W prevents entire network outages during system updates and reboots
• The Pi Zero 2W consumes just 1-2.5 watts at idle compared to 10-35 watts for mini PCs and 60-100 watts for desktops
• For single-purpose DNS filtering, the $15 Pi Zero 2W offers better reliability and efficiency than repurposing a spare PC

The hidden risk of running Pi-hole on a shared PC

Every time I had to reboot my mini PC to update a Docker container, a VM, or just to apply patches, my entire home network went down with it. My family often noticed that before I did. My mini PC wasn't struggling with the Pi-hole's load, but there was a simpler, yet just as problematic issue. I ran a DNS service on my home server and totally overlooked the side effects of system downtime. DNS was just another service in that box. When the host went down for any reason, it took down the whole network, including DNS, not just the service I was actually trying to fix.

Moving the Pi-hole back on to a Pi Zero 2 W wasn't about resources. I wanted to match the hardware to the job it actually demands and keep it out of the blast radius of everything else.

Why Pi-hole doesn't need a powerful computer

Pi-hole's dashboard sits idle while pure DNS resolution does the actual work. It checks domains against its gravity database, then forwards or blocklists the query. The list is already loaded in memory. There's no heavy CPU load since there's no compression or transcoding.

That's why the Pi Zero 2W's quad-core Cortex-A53 barely breaks a sweat handling a busy household with dozens of smart devices that generate massive query volumes. A mini PC's multiple cores and desktop-grade RAM aren't headroom for this job; they're idle silicon.

Power, space, and noise: the hidden costs of over-engineering

An old desktop can draw as much as 60–100 watts when idle, depending on the hardware. A mini PC is leaner, but still draws about 10–35 watts at idle before you factor in the attached storage and peripherals. The Zero 2 W idles at 1–2.5 watts.

Running a Pi-hole on Zero 2 W costs a couple of dollars a year in electricity. Even the mini PC's full idle power draw is hard to justify for a service that barely touches it. Something similar can be said for physical size. A full tower needs more dedicated space and sufficient ventilation.

When a mini PC's fan cycles on and off in response to load spikes, it's not that noticeable during the daytime, but you'll only notice that at midnight when everything in the house goes quiet. The Zero 2 W runs cool without fans and can fit inside an Altoids tin.

When a spare PC still makes sense

Using a spare PC seems justifiable if you run multiple services on it besides Pi-hole. For instance, turning an old PC into a media server or DIY NAS is a natural solution. Even a mini PC running Docker, a NAS share, media servers, and VPN endpoint puts the machine's processing and RAM to actual use.

That's why using a nimble SBC like Pi Zero 2W for a single project like Pi-hole makes sense. But if you add anything more, the board might choke. Running a Pi-hole on a full Linux box or in a Proxmox-based VM is more approachable than limiting yourself to a headless Raspberry Pi reachable only over SSH.

If your spare PC already hosts several self-hosted services, adding a Pi-hole won't strain the hardware. But there's a risk that has nothing to do with resources. Whenever your PC needs a reboot to apply an update or patch, the DNS server goes down for the entire network.

Pi Zero 2W limitations and considerations

Most services on the home server fail gracefully. For instance, Jellyfin buffers, a file share times out and retries. But a DNS failure takes the network down with it. Dedicated hardware for Pi-hole sidesteps that entirely, letting you break, rebuild, and tinker with your home server without losing internet access.

The most overlooked aspect of Pi Zero 2W is that it's Wi-Fi only. It may not be as reliable as a stable wired connection. For that, you can use a HAT and a case with an Ethernet port, or an Ethernet adapter. Pi-hole runs like a charm on a single board, which is tasked with doing only one thing well. To avoid data corruption, you can use an A2 microSD card, a rating that indicates it is optimized for random read/write rather than sequential speeds.

The hardware steps aside to handle DNS tasks while you continue experimenting in your home lab. The Pi Zero 2W can handle Pi-hole with Unbound as a recursive resolver without complaints. It's a combination Pi-hole's documentation recommends as a complete privacy setup and still works on Zero 2W.