Risking sounding like a broken record, I always suggest Tiny/Mini/Micro 1L form factor office PCs. Lenovo, Dell, and HP all create ultra small office PCs that make great low power servers. A Pi will use 5-9w at idle, while these PCs will use 11-13w idle. They also use more standard components such as NVME drives, 2.5" drives, and replaceable RAM. Easy to find under $100 USD used, I'm sure you can find them under 100 euro.

Try a used laptop. Cheap, power efficient, built in UPS, small. Can be quite powerful and some are even upgradable

As a point of reference regarding power consumption:

I've been running a desktop non-stop for the last ten years (built as a gaming rig) as a file/media server, so it's probably the worst thing you can run this way, power-wise. Has an 800 watt power supply, running windows.

I've done the math many times, costs me about $1/day in power at mostly idle.

Just presenting a worst-case example as a guideline.

I've recently spun up a Raspberry Pi Zero W for PiHole, DHCP, DNS, Tailscale, Joplin and Bitwarden. It's maximum power draw is TWO WATTS. Haha

Currently running a watt meter on the desktop, should have some decent actual numbers from it soon, but can't imagine idle is any less than 50 watts.

So there's two extremes. Don't be me (looks like you aren't!)

Edit: I wouldn't recommend the Zero W for this, it's underpowered. I'm already overloading it with just PiHole and Tailscale, honestly.

Look into a NUC on ebay. I was able to snag a new 11th Gen i3 for 200 eur. Power draw is about 7w with a headless Debian. Running a media server, nextcloud, pihole, an arr stack and I'm planning to add home assistant and a zigbee bridge which I now run on a pi.

If you aren't planning to run to much on it a rpi4or5 will actually be enough and these things can draw 15 on absolute max load.

I have an Intel NUC I got on eBay for £50. It’s running 30 containers, 10W draw

Lenovo m900 tiny. Low cost and power.

A raspberry pi or orange pi could definitely run all of those things at very low power consumption.

Any Intel NUC(the small 4x4 ones) 8th gen or forward will fit the bill.

Not to state the obvious one, but there's always the Raspberry Pi.

The supply has gotten better on those, so you can probably pick one up in your price range, and the power draw is super minimal.

Hey fellow european!

Tinytronics.nl -> Pi4 model B 8GB: 87€ and in stock. The 4GB model is 68€. They also have orange Pi for a higher budget.

Kiwi-electronics.com -> Pi 4 model B, 4GB? 63€. They also have all the pi accessories you could want.

If you are going to use paperless for important documents, and if you want to not lose data for sure, get a 1TB cheap HDD or something and a USB3.0 adapter. SD cards will eventually fail.

Otherwise, get an old used laptop 2nd hand. I used an old HP probook G1 laptop for about a year for my server. It didn't use much power at all.

HP EliteDesk 800 G3 Mini (or equivalent)? You can get them for pretty cheap on eBay.

A cheap android box + armbianOs is also an option if you're looking for low power. I have a 7watt one that's running 24/7 for the last few years.

@pathief I think what you are looking for is intel n100 since it only uses like 6-watt TDP, but before jumping to that, you should look at Heaven video. If you only want to run for a year or two, maybe the older CPU is much better.

https://www.youtube.com/watch?v=PisIPpbMkTc

I hope you found what you are looking for.

Have a look at the ServeTheHome site and channel on youtube ... he's done a load of good reviews of AliExpress devices and some tiny/mini/micro devices (think thinclients)

He covers power consumption and some interesting points (like which recent multi-Gb NICs are supported by pfSense / Proxmox / etc)

Just watching those should at least help you decide what you need.

I was going to build my own virt server and I ended up with a low power, silent, passively cooled box to run all my VMs in... for much cheap.

At around 80 euros then for lowest power you should go Raspberry Pi, for most performance while still being low power an old business laptop is fine, and since you don't need the screen you can buy one with a broken screen.

A refurbished elite desk sff PC works great.

A used Android pixel phone. You can root it and install Pideploy and run PiHole through it.

I have an old Pixel 3a doing exactly this. The other services I don’t quite know if they have an Android implementation.

Doesn’t suit your every use case, but I figured I’d share.

My whole "homelab" is made of either things I literally found in the trash, hand-me downs and 2nd part stuff I got for extremely cheap. It's no speed deamon, but it's got 8cores, 16GB ram and gigabit... What I'm trying to say is, that is most likely also an option for you and there is no reason to buy the latest and greatest of hardware for running simple things like pi-hole. As for the electricity bill, unless you're running something computationally intensive 24/7 or just a ton of hard drives, I wouldn't worry about it.

This serves a couple services, incl. kitchenowl and paperless-ngx very fine for me.
Once, I got it for around 45€.

I just bought a cheap Intel i3 10100T that have a TDP of 35W.
There is a bios option to reduce that to 25W.
Thoses are not sold to end users and must be purchased through craiglist or equivalent.