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used mini pcs

Agents that never sleep

A used mini PC as an always-on AI agent server

An AI agent server is a small, always-on computer that runs the agent harness, its tools and its browsers around the clock while the model itself answers from the cloud. A used business mini PC is a good fit for the job: it idles at around the wattage of a light bulb, has room for 32 to 64 GB of RAM, and costs nothing per month once you own it.

What you need

SpecRecommendedWhy
CPU generationIntel 8th gen or newer, or Ryzen 4000 (Renoir) or newer; 6 cores or more preferredThe agent loop itself is light, but the things agents do (installing packages, running test suites, building code, driving a browser) are bursty CPU work. A 6-core Coffee Lake or Ryzen PRO GE chip lets two or three agents run in parallel without queuing. Claude Code needs an x64 or ARM64 processor, which every catalog model has.
RAM16 GB minimum, 32 GB comfortable, 64 GB for many parallel or browser-heavy agentsClaude Code lists 4 GB+ RAM as its floor. Anthropic's Agent SDK hosting guide suggests 1 GiB RAM per agent as a starting point and warns that memory grows with session length and tool use. Headless browsers, Docker containers and language servers stack on top of that.
Storage typeNVMe SSD, 500 GB or largerThe Agent SDK guide suggests 5 GiB of disk per agent as a baseline. Repos, node_modules folders, browser binaries, Docker images and session transcripts add up quickly, and NVMe keeps installs and git operations fast.
NICsOne wired 1 GbE portAgent traffic is mostly outbound HTTPS to the model API plus occasional webhooks. Bandwidth is not the bottleneck; a wired connection is simply more reliable than Wi-Fi for a box that has to stay reachable.
Idle wattsAbout 10 to 15 W at the wall for a 1-liter business tinyAn agent box spends most of its life waiting for the next job, so idle draw is what you pay for. ServeTheHome measured 11 to 14 W idle on a ThinkCentre M720q and described its whole first batch of tiny/mini/micro test units as about 10 W idle.
NoiseFan-cooled 1-liter tiny is fine; near-silent at idleServeTheHome found the M720q's idle noise not significant and the M920q audible only under sustained CPU load. Agent work is bursty, so the fan spends most of its time near idle.
Remote managementNice to have: Intel vPro (AMT) or AMD DASHOn a headless box, out-of-band management lets you power-cycle it or reach the BIOS without walking over with a monitor. Lenovo's PSREF lists Intel AMT 12.0 on vPro M920q configurations and DASH 1.2 on M75q Gen 2 units with the Realtek RTL8111FP NIC.

Which mini PCs fit

A model gets the “AI agent server” badge when it:

  • Intel 8th gen or newer, Intel N-series, or AMD Ryzen 2000 or newer (not Ryzen Embedded)
  • Takes at least 16 GB of RAM (manufacturer's stated maximum)
  • Has an M.2 slot that takes an NVMe SSD
  • Has wired Ethernet

Rules use manufacturer specs only. 36 of 58 catalog models qualify.

Best overall

Lenovo ThinkCentre M75q Gen 2 Tiny

Lenovo's PSREF lists up to 64 GB of DDR4-3200 in two SO-DIMM slots, Ryzen PRO GE chips up to 8 cores and 16 threads (Ryzen 7 PRO 4750GE/5750GE), an M.2 NVMe slot plus a 2.5-inch bay, and DASH remote management on units with the RTL8111FP NIC. That is enough memory for several agents with headless browsers side by side in a quiet 1-liter box.

On eBay now: The lowest ask at about $140 delivered from a 99.8% seller, for a quad-core Ryzen 3 PRO 4350GE with 8 GB. The title cuts off before storage, so ask whether a drive and adapter are included before you count it as complete. $139.99

View on eBay ↗: Lenovo ThinkCentre M75q Gen 2 Tiny Ryzen 3 Pro 4350GE 3.50 GHz 8 GB DD

Best value

Lenovo ThinkCentre M720q Tiny

One of the most common off-lease tinies. Lenovo's PSREF lists 8th/9th-gen T-series CPUs from Celeron up to the 8-core i7-9700T and i9-9900T (the six-core i5-8500T and i7-8700T are the common used configurations), two DDR4-2666 SO-DIMM slots (32 GB official), an NVMe slot plus a 2.5-inch bay, and an Intel I219-V NIC. ServeTheHome measured 11 to 14 W idle. A six-core unit with 32 GB handles a few agents comfortably.

On eBay now: The lowest price on a complete unit: an auction at about $73 delivered with 1 bid, so expect it to climb. It's a quad-core i3-8100T with 12 GB and a 480 GB SSD, and the title doesn't mention the adapter. $72.74

View on eBay ↗: Lenovo ThinkCentre M720q Intel Core i3-8100T 3.1GHz 12GB 480GB SSD

What it costs to leave on all year

An always-on box spends almost all its time near idle, so idle draw sets the bill. The math:

idle watts × 24 h × 365 days ÷ 1,000 = kWh per year · kWh × $0.1831/kWh = dollars per year

MachineIdlekWh / yearCost / year
1-liter business tiny (Lenovo ThinkCentre M720q, Pentium Gold G5400T), idle at the wall, measured by ServeTheHome, low end source11 W96.4$17.64
1-liter business tiny (Lenovo ThinkCentre M720q, Pentium Gold G5400T), idle at the wall, measured by ServeTheHome, high end source14 W122.6$22.46
Beelink SER5 (Ryzen 5 5500U / 5600H / Ryzen 7 5700U) (measured, 5.3 W upper figure) source5.3 W46.4$8.50
Minisforum UM790 Pro (Ryzen 9 7940HS) (measured, 7 W upper figure) source7 W61.3$11.23
Intel NUC 13 Pro (NUC13ANK / NUC13ANH) (measured, 8 W upper figure) source8 W70.1$12.83
Beelink SER6 Pro (Ryzen 7 6800H / 7735HS) (measured, 8.2 W upper figure) source8.2 W71.8$13.15
ASUS NUC 14 Pro (measured, 9 W upper figure) source9 W78.8$14.44
Dell OptiPlex 3070 Micro (measured, 10 W upper figure) source10 W87.6$16.04
Beelink GTR6 (Ryzen 9 6900HX) (measured, 10 W upper figure) source10 W87.6$16.04
Dell OptiPlex 7080 Micro (measured, 11 W upper figure) source11 W96.4$17.64

Electricity at 18.31¢/kWh, the U.S. average residential price, July 2026 (EIA). Your rate is on your bill; swap it into the formula. Real draw rises above idle whenever the box is working, and depends on drives, RAM, BIOS power settings and the OS.

What the box does, and what it doesn't

Be clear about the split before you buy anything. When you run Claude Code or an app built on the Claude Agent SDK, the model runs in Anthropic's cloud and is reached over the API. Claude Code's own requirements list an internet connection as mandatory and a Pro, Max, Team, Enterprise or Console account. The mini PC runs everything around the model: the agent loop, the shell it executes commands in, git, your test suites, MCP servers, headless browsers, and the scheduler that kicks jobs off at 3 a.m. That is why a modest used box works here, and why you do not need a GPU for this job. If you want the model itself to run on your hardware, that is a different and much heavier workload; see running local LLMs on a mini PC.

Claude Code and Agent SDK requirements

Claude Code's published system requirements are modest: macOS 13+, Windows 10 1809+ or Windows Server 2019+, Ubuntu 20.04+, Debian 10+ or Alpine 3.19+, 4 GB+ RAM, and an x64 or ARM64 processor. The native installer does not need Node.js at all; only the optional npm package asks for Node.js 22 or later. If you build your own agent with the Agent SDK, the runtime is Python 3.10+ or Node.js 18+, and the SDK bundles its own Claude Code binary.

Sizing is where the SDK documentation is most useful. Each agent session is a separate long-lived subprocess with its own shell, working directory and transcript on disk. Anthropic suggests 1 GiB RAM, 5 GiB disk and 1 CPU per agent as a starting point, says memory grows with session length and tool activity, and gives a simple formula: agents per host equals host RAM minus overhead, divided by the peak RAM one session actually reaches. Measure a real session under your real tools rather than trusting the floor. In practice that means 32 GB is a comfortable target for a few concurrent agents, and 64 GB is where browser-heavy fleets stop fighting each other.

Scheduled agents with cron or systemd timers

For unattended jobs, Claude Code's non-interactive mode is the building block: `claude -p "…"` runs one task and exits with code 0 on success and non-zero on failure, so cron or a systemd timer can branch on the result. The docs recommend `--bare` for scripted runs (it skips auto-discovered hooks, plugins and MCP servers and needs `ANTHROPIC_API_KEY` set), `--output-format json` returns the result plus an estimated cost figure, and `--permission-prompts none` denies anything that would otherwise wait for a human. Pair that with a tight `--allowedTools` list and a dedicated Linux user, and a nightly dependency-update or report-writing agent is a few lines of config.

Browser agents are the heavy part

Agents that drive a real browser through Playwright are the most demanding thing you will put on this box, because every session is a full Chromium instance. Playwright's current requirements are Node.js 22, 24 or 26, and on Linux it lists Debian 12/13 and Ubuntu 22.04, 24.04 and 26.04 on x86-64 or arm64. Playwright does not publish a RAM figure per browser, so budget by measuring: launch your typical number of sessions, watch peak memory, and size up from there. That is the main reason the picks on this page favor 64 GB-capable machines. Ubuntu 24.04 LTS satisfies both Claude Code's and Playwright's support lists, which makes it the low-friction OS choice.

MCP servers and webhooks

MCP servers come in two standard transports. With stdio, the agent launches the server as a local subprocess, so it costs a little RAM per server and nothing else. With Streamable HTTP, the server is an independent process with its own endpoint; the spec says local servers should bind to 127.0.0.1 rather than every interface and should authenticate connections. Keep them on localhost and you avoid most of the risk.

Webhooks (a GitHub push, a form submission, a payment event) need a way in from the internet. Instead of forwarding a port on your router, use a tunnel. Cloudflare Tunnel's `cloudflared` makes an outbound-only connection, so the box needs no publicly routable IP and you can block all inbound traffic. Tailscale Funnel routes public traffic to a local service on ports 443, 8443 or 10000, TLS only, is available on all Tailscale plans, and has bandwidth limits you cannot configure, which is fine for webhooks.

Why a mini PC beats a laptop or a VPS for this

  • Versus an old laptop: a laptop wants to sleep when the lid closes, rides on Wi-Fi, and keeps a battery sitting at full charge for months. A mini PC has none of those habits, takes a wired connection, and can be set in BIOS to power back on after an outage.
  • Versus a cloud VPS: a VPS bills every month forever; a mini PC is a one-time purchase plus electricity. Your repos, browser profiles, API keys and the files agents work on stay in your house instead of on someone else's disk.
  • Where the VPS still wins: a data center has redundant power, a static IP and nobody tripping over the cable. If your agents serve paying customers, host the public endpoint in the cloud and let the home box do the private work.

Power is the running cost that matters. At the 11 to 14 W idle that ServeTheHome measured on a ThinkCentre M720q, the yearly electricity estimate on this page stays small, and agent bursts barely move the average. Anthropic's own hosting guide points out that model token spend typically dwarfs infrastructure cost, so the box will rarely be your biggest line item.

How much machine you need

If you are choosing between the three big business brands, our ThinkCentre vs OptiPlex vs EliteDesk comparison covers the differences in RAM limits, storage layout and remote management.

Setup outline

  1. 1Before you pay, ask the seller whether a BIOS supervisor (administrator) password is set. With one in place you cannot change boot order, UEFI or Secure Boot settings, so get it removed or skip the unit.
  2. 2On first power-up, open BIOS setup and look on the security page for a Computrace or Absolute setting. Absolute's persistence module lives in the firmware of machines from many PC makers and can reinstall its agent after a wipe, so if it shows as activated, ask the seller for proof the previous owner released the device.
  3. 3Update the BIOS to the latest release from the maker's support site (look it up by serial number). Old firmware is the usual cause of odd memory and NVMe behavior on off-lease units.
  4. 4Install RAM as a matched pair so the memory runs dual-channel, and fit an NVMe SSD of 500 GB or more.
  5. 5Run a full pass of MemTest86+ from a USB stick before installing anything. Agents that crash at random on a used box are usually bad memory.
  6. 6In BIOS, set the machine to power on after AC loss so it comes back by itself after an outage, then install Ubuntu Server 24.04 LTS.
  7. 7Create a dedicated non-admin user for agents, install Claude Code with the native installer, and run `claude doctor` to confirm the install.
  8. 8If you use browser agents, install Node.js 22 or later and Playwright with its Chromium build and system dependencies.
  9. 9Schedule jobs with systemd timers or cron calling `claude -p` (with `--bare`, a narrow `--allowedTools` list and `--permission-prompts none`), and expose webhooks through Cloudflare Tunnel or Tailscale Funnel instead of opening router ports.

AI agent server: common questions

Does the mini PC run the AI model?

Not for Claude Code or Agent SDK agents. The model runs in Anthropic's cloud and is reached over the API; the mini PC runs the agent harness, its shell, tools, MCP servers and browsers. That is why a used 1-liter business PC is enough. Running the model locally is a different job; see local LLMs on a mini PC.

How much RAM do I need to run Claude Code 24/7?

Claude Code itself lists 4 GB+ RAM. For an always-on server, plan on 16 GB for one or two agents without a browser, 32 GB for several agents or Playwright, and 64 GB for many browser sessions at once. Anthropic's Agent SDK guide suggests 1 GiB per agent as a floor and recommends measuring the peak memory of a real session.

Is a mini PC better than a VPS for AI agents?

For private agents, usually yes: no monthly fee, plenty of RAM in a one-time purchase, and your files and credentials stay at home. A VPS is better when you need a static public IP, data-center uptime, or a service that customers depend on.

Can an Intel N100 mini PC run agents?

It can run one or two light scheduled agents. Most N-series machines are limited to 16 GB on a single memory channel, which gets tight once headless browsers or Docker are involved. A used 6-core business tiny with 32 GB is the safer buy. See N100 vs N150 vs N305.

How do I receive webhooks without opening ports?

Use an outbound tunnel. Cloudflare Tunnel's cloudflared connects out to Cloudflare so you can block all inbound traffic, and Tailscale Funnel publishes a local service on port 443, 8443 or 10000 over TLS.

Is it safe to leave an agent running unattended?

Scope it tightly. Run it as its own user, list only the tools it needs with --allowedTools, use --permission-prompts none so anything outside that list is denied instead of waiting, keep MCP servers bound to localhost, and never give the agent account admin rights.

Sources

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