Watts vs Pounds: Pi 5 or a Second-Hand Mini PC for an Always-On Home Server?
Every home server conversation in this country starts in the same place: 'the Pi sips power, though.' It does. But before you let a wattage argument choose your hardware, it is worth doing the sum properly, because at current UK tariffs the electricity difference between a Raspberry Pi 5 and a second-hand business mini PC is roughly the price of a pub lunch per year. That is not nothing, but it is rarely the thing that makes you happy two years later.
So let's do the boring bit first, then get to the bits that actually matter: noise, storage, transcoding, and what you can realistically buy for £150 in late 2026.
The only power maths you need
One watt running continuously for a year is 8.76 kWh. On a tariff of around 25p per kWh, that works out at roughly £2.20 per watt per year. Memorise that and the rest is arithmetic.
| Route | Typical average draw | kWh/year | Cost/year at 25p | Realistic 2026 outlay |
|---|---|---|---|---|
| Raspberry Pi 5, 8GB, NVMe | 4–5 W | ~40 | ~£10 | £140–£160 |
| Used mini PC (i5-8500T class) | 8–11 W | ~80 | ~£20 | £120–£170 |
| Old laptop doing server duty | 10–14 W | ~105 | ~£26 | £0 (you own it) |
| Two-bay NAS with two 3.5in drives | 15–20 W | ~150 | ~£38 | £250+ |
That's the whole story: the Pi saves you about a tenner a year over a mini PC. Over five years, roughly £50. Meaningful, but it is not the £150-versus-£150 decision people pretend it is—especially when you remember the standing charge on your electricity bill is around 60p a day no matter what you plug in.
What £150 actually builds
The Pi route. A Pi 5 with 8GB lands around £76–£86 depending on stock, and you'll want the official 27W USB-C power supply (about £12), a case (£10), an active cooler (£5) and an M.2 HAT so you can boot from NVMe (£12). Add a 500GB NVMe drive for £35 and you're at roughly £150. Do not, under any circumstances, run this off a microSD card and expect it to survive eighteen months of Home Assistant writes.
The mini PC route. Ex-corporate stock is everywhere in the UK—Dell OptiPlex Micro, Lenovo M720q, HP EliteDesk Mini, mostly 8th to 10th gen Intel. A tidy i5-8500T with 8GB and a 256GB SSD is £110–£150 delivered. Swap in a 1TB SATA SSD for £50 and you've spent a little more than the Pi, with vastly more headroom.
Where the Pi 5 earns its keep
It is tiny, it is genuinely near-silent at idle, it has GPIO if you want to wire up a doorbell or a temperature sensor, and the community around Home Assistant OS images is enormous. Backup, DNS, Pi-hole, a bit of Docker, a small file share—all fine. Power consumption stays low, and if it dies you buy another one for the price of a takeaway.
What it does not like: video transcoding. There is no QuickSync, so Jellyfin will either direct-play or fall over. Storage is a single NVMe lane unless you start hanging USB drives off it, which is exactly how people lose data. And while arm64 Docker images are now the norm, you will occasionally hit a container that only ships x86 and spend a Saturday morning on workarounds.
Where the mini PC quietly wins
The 8th-gen Intel iGPU handles hardware transcoding for a couple of simultaneous Jellyfin streams without breaking a sweat, which turns 'media serving' from a theoretical capability into a real one. You get two RAM slots, a 2.5in bay in most micro chassis, and enough CPU to run Frigate with a few cameras without the fans screaming. It runs x86 builds of everything, forever, without checking architecture tags.
Downsides: it idles higher, the fan is audible under sustained load, and second-hand units often arrive missing their external power brick—Dell's 65W barrel adapters are cheap and generic ones work, but factor £15. Ask the seller about BIOS passwords before you pay, and check whether the storage is a real SSD or eMMC.
When neither is the right answer
If your priority is photos and files that must not vanish, a two-bay NAS from Synology or QNAP is the honest recommendation. It costs more, draws more and will not run Home Assistant well, but it does redundancy and scheduled backups without you thinking about it. That is worth £250 to a lot of households.
If your priority is 'free', an old laptop is genuinely underrated: the built-in battery is a mini UPS during power cuts, the screen can be disabled, and it costs nothing. Just set it to do nothing when the lid closes, expect one SATA bay, and accept that a ten-year-old hinge will eventually win.
Two checklists before you click buy
Buying the Pi: official PSU only; active cooler, not the passive case; NVMe HAT plus a reputable drive; boot from NVMe, not SD; a case with room for the HAT; buy from a UK seller with stock, not a marketplace reseller at a markup.
Buying the mini PC: 8th-gen Intel or newer (that's the QuickSync generation that matters for HEVC), or a Ryzen 2400GE and up; confirm the power adapter is included; check for 2×4GB rather than 1×8GB so you can upgrade later; ask about BIOS locks and Computrace; buy from a UK refurbisher with a returns window.
One last thing: measure it
A £13 plug-in energy monitor will tell you what your actual build draws over 24 hours, which is far more useful than any table. Plug it in for a week, look at the total, and decide whether a tenner a year is worth changing your plans over.
Spoiler: it probably isn't. Buy for software compatibility, storage and transcoding. The watts will look after themselves.
