The NUC market is soon gone, so the idea might not be that bad.
You all need to look broader.
RPis is not only used for running HA and they are beating a NUC or any other PC in accessories.
I have a little project going where I want a RPi with an ePaper monitor connected to SPI, sensors for temperature, humidity and light and a soundcard for warning/messages.
This should easily be run on a RPi3, but if I want to add voice Assistant with wake word, then I would maybe need a RPi4 or better and if I want to play music on that project too with echo cancellation, beamforming and other sound features on the voice Assistant, then a RPi5 might be a good choice.
This project would not be so essily possible on a PC
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Wondering about a CM5. Compute Module 5.
Might it be pin compatible?
Highly unlikely.
The RPi5 have new features, like a PCIe port, which would require CPU connections.
Depends on how many free pins were on the CM4 connector. My guess is there are enough. CM4 has 2 100 pin connectors.
I’m seeing a lot of mention of performance per currency unit spent. But at what cost would this be? I think, for an always-on device, the amount of energy consumed while idle is an important factor as well.
I’ve seen people use an old small form factor PC for home automation, thinking they were saving some money, instead of going with something new, like an RPI4, because “more performance”. This old small form factor PC was using 50 Watt idle, instead of 3 for a more than adequate RPi. So this device added over 123 Euros to their utility bill each year. (Assuming 30 cents a kWh.)
Saving some money in fact ending this person up with spending money within a year. Each watt of 24/7 additional power consumption adds about 2,6 euros or dollar to your yearly bill when assuming a 0,30 cent price for electricity. Do not underestimate how quickly this adds up.
Also, who needs a ton of performance for Home Assistant in most cases. I’ve been running HA on an RPi 4, 4GB with a 32 GB SD card without issue. (I have daily backups and 2 spare SD cards at the ready in case an SD card fails on me.)
Also the pricepoint mentioned of some Nuc PCs. 77 dollar. They are listen for over over a 100 nowadays. And then you also need to add a bunch of peripherals to make it all integrate, just like with an RPi. And if you go with an RPi 5 4 GB, a case, a power supply, and a Raspbee 2 board for Zigbee, I think you end up with a neat package, nothing much sticking out out it, that works for many use cases. And to be honest, an RPi4 is still more than capable enough right now. (Still going to upgrade to an RPi 5 or a Yellow with a CM 5 once available, provided the power consumption is in the same range.)
(I love the Home Assistant Green and Yellow btw. Not the cheapest options, but they get first party support and for a device that’s central to your home, that is a big argument for these devices.)
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From the two or three decades ago? Did you build that one yourself and messed up the power manangement? 
Our last HA Server with a CPU now almost 10 years old actually had a lower power consumption than a Raspberry while still having a better performance. The thing was even smaller than a PI and doesn’t rely on a sd card for storage and was conveniently powered via microUSB and
This thing like most x86/x64 often have a better power management than SBC’s. For example a Raspberry Pi 4 is idling with almost 3W while our device was happy with just 1W 
Correct, and the Raspberry Pi 4 was/is quite bad in this scenario! Worst than a random Intel CPU from the last decade 
Correct, people buying a Raspberry thinking it is low power and ending up with a energy bill 3 times higher than if they would have used a old device from the drawer 
Think of the following: Demanding task coming in your Pi 4 is blocked for couple of seconds/minutes because of 100% cpu usage. Another device (maybe 10 years old) with a 7x higher performance doesn’t need the 100% usage and allows to use the HA web ui all the time while your Raspberry craps out and is unresponsive 
Specification comparison:
| Processor | Intel Atom Z3735F | Broadcom BCM2711 | ||||||
|---|---|---|---|---|---|---|---|---|
| Market (main) | Notebook | Single-board computer | ||||||
| ISA | x86-64 (64 bit) | ARMv8-A (64-bit) | ||||||
| Release date | Q1 2014 | Q2 2019 | ||||||
| Lithography | 22 nm | 28 nm | ||||||
| Cores | 4 | 4 | ||||||
| Threads | 4 | 4 | ||||||
| High performance cores | 4 Cores 4 Threads @ 1.33 / 1.83 GHz | 4x ARM Cortex-A72 @ 1.5 GHz | ||||||
| TDP | 2 W | 8 W | ||||||
| (Multi-core / watt performance) Performance / watt ratio | 938 pts / W | 128 pts / W |
As mentioned it is not the same device 
No? Other than a SBC the thing is complete and works out of the box as unlike berries it comes with case, cooling, flash, rtc, psu 
If you are REALLY interested in saving power you wouldn’t have bought/used a Raspberry Pi 4 in the very beginning 
Benchmarks indeed are the opposite of real life scenarios. Little more than just a grain of salt necessary
Well, it does to some extended. As higher the performance per Watt is as lower is the power consumption. Why is that? Because the device with a higher performance/Watt ratio is more efficient
See the table above? This 10 year cheap atom CPU has a TDP of 2W compared to 8W for the Raspberry SOC. Bottom line the raspberry still performs worse while producing 4 times the heat which is just wasted energy 
If i’ve read correctly NUC will be Asus in the future. Things was, i think, sold to Asus (or merged…).
Correct.
Even if the trademark “nuc” died with Intel, there will continue to be many using the basic form factor.
Nuc-luke pcs aren’t going away anytime soon.
I’m seeing a measured power usage on my RPi4 of 0.11 kWh a day. That’s an average usage number… calculated from over a year of usage. Measured with an uncertified power meter. (Zigbee powerplug.) Not seeing blocked UI on HA… So that’s interesting. 
I like your elaborate answer. Taking notes here. That 50 power usage might be a crap power supply… that’s a good one.
Why are you looking at TDP? That’s just a measure of radiated heat when under load? The key being “under load” I’m mostly interested at energy consumption under low load conditions.
Very wishful “measurements” you got there 
Just checking the first 3 results I get for idle power of a RPi4 
Raspberry Pi 4 B
Pi State Power Consumption Idle 540 mA (2.7 W) ab -n 100 -c 10(uncached)1010 mA (5.1 W) 400% CPU load ( stress --cpu 4)1280 mA (6.4 W) Power Consumption Benchmarks | Raspberry Pi Dramble
Raspberry Pi 4 Power Consumption
The power consumption of the Raspberry Pi 4 varies – when idle it tends to consume around 3 to 4 watts, with an increase of 0.5 watts for each core that is then busy, up to a maximum of 6 watts when all four cores are working.
Raspberry Pi Power Consumption Guide (2024)
Model IDLE LXDE loaded 1080 resolution video 400% CPU loaded Raspberry Pi 4B 575 mA 885 mA 600 mA 1280 mA […] on the IDLE state of the Raspberry Pi 4, the power is 2.875 Watt which means the Raspberry Pi is consuming moreover when the load is increased on the Raspberry Pi.
How Much Power Does Raspberry Pi Consume While Operating
So all others idle around 2.7 - 4W but you manage with less than half a Watt? Congrats I would say - or - junk of a power meter you have
4.5 watts if my maths work…
0.11 * 1000 / 24 is what I’m supposed to do right?
I don’t get why need to tell me I have a junk power meter. Could very well be. That’s why I took a longer duration measurement and calculated daily usage off of that.
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That depends on Intel.
I got the understanding that they would stop producing the chip series too.
There are plenty of nuc form factor pc’s based on AMD chips and alternate Intel chipsets. The nuc chips have generally just been minor variations of laptop chips. Laptop chipsets will still be around.
Low cost, small form factor, low power pcs are not in danger of disappearing.
Your math works Had somehow s(h)aved a power of 1.1w in my head and not the energy kWh you posted
Our (now old) HA server based on that 10 year old atom was happy with just 1W idling around - something a Raspbbery Pi 4 did never achieve 
The thing was even capable running of 5V 1A PSU (5W max output without the additional losses in the cable!) - only downside was it never never reached it’s turbo frequence - still was it was running stable. 
I’ll be excited and ready to purchase when the CM5 is eventually developed and released. Would also be exciting if it could support connectivity to a CM4 based development board. Could upgrade my Home Assistant Yellow PoE in that instance.
Using a 1TB nVME SSD with my HA Yellow using the CM4 Lite.
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Yes, that math makes sense to me as well.
So, here in the USA, with the average cost of power being about $0.125 /kWh, this works out to be something like
4.5W/h * 24h/day * 365day/year / 1000W/kW = 39.42kWh used per year * $0.125 = $4.93 per year.
Power usage might not be much of a deciding factor purely from a financial perspective, at least in the USA. Obviously, in other parts of the world, electricity costs are much, much higher. This could affect one’s decision on the choice of platform. Or, if one was trying to run their household off of solar or wind, every little bit helps.
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I agree. I too hope the HA Yellow will eventually be able to enjoy a higher performing CPU upgrade via the CM4 module interface. One concern, however, would be whether or not the HA Yellow board would be capable of providing enough power for the RPi 5’s beefier CPU. My HA Yellow is running off of PoE, and I do not know what the max power output the Yellow’s onboard circuitry is capable of.
When CM4 was announced, part of the spin on the new design was that future revisions could use the same connectors in a plaga and play manner.
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I hate mini-HDMI !
All my Pi’s are headless servers.
I’m connecting one basic screen when I really really really need one, when SSH is broken and when I have to, I’d like to connect the first HDMI cable that I’m picking without an adapter.
Time to move to something else.
Ever since the 1B+, I’ve faithfully tracked the Pi’s evolution, but this is where I draw the line.