efficiency The unsexy topic of power consumption

[mggevaer]

Hi all,

Looking into buying a life-time license but trying to do some math first on total cost of ownership.

One often claimed benefit of DIY systems is the ability to run low cost second hand hardware. However, newer hardware tends to be more energy efficient. But is this also the case for idle power?

1W of additional idle power consumption translates to about ~4USD/year where I live. So saving a couple of watts can add up.

Is there a specific niche for this sort of thing? Perhaps old office pc's, or mini pc's have especially favourable idle power consumption?

[UncleMikey]

You could run it in a vm on a macbook... I hear those are SUPER efficient lol. Some mad lad already did it I think.

[Manderis]

I am also wondering about that. 

I am not sure how you came up with the 4 USD/Year. I guess you live somewhere with more expensive power than Germany. 

24 Wh each day

x 365 days

8,76 kWh x individual USD/kWh

@0.30 €/kWh or 0.316 USD/kWh

For me it comes out to around 2.62 €/(W x year) or 2.77 USD/(W x Year) 

 

I would love to go with some old optiplex (I have a without ram and cpu sitting in my basement) but I am worried about power consumption. 5th or 6th Gen Intel. 

If I get a new ish thinclient with a modern mobile cpu ~200 USD I can get with drives below 25 W max power and have a reasonable idle, maybe below 10 Watts. 

With an old Gen Intel optiplex I worry about 50 - 70 W idle (guesstimate) for the whole system. 

That would make more than 150 €/Year in electricity cost. 

There are a few mini pc/thin clients availabile like a blackview Mp100 ryzen 5700u (ebay ~220 €) or a HP T640 ryzen 150G (eBay 69 €, nice) @10 W idle. But pcie expendability and sata power is questionable. For pcie I can probably use the m.2 slot for maybe 4x sata/sas. 

 

Additionally you are dependent on on board grafics for transcoding. So maybe I should look to something more modern. 

Case is not a problem, I have a 3D printer to build something 

[ShadowChaser]

I am smitten with a specific supermicro board that has the Xeon D-1521. It's an embedded Broadwell (intel 5th gen) Xeon that has a TDP of 45W, which is higher than I'd like, but has dual 10GbE onboard. Official ECC memory support and the ability to add 4 PCIe devices with bifurcation means this is a pretty good start for a full size build in my opinion. There's a modern alternative in the Minisforum BD790i series that uses a 7940HX or 7945HX with a configurable TDP of 55-75W if you need extra cpu horsepower

If you want to go smaller and sacrifice some expansion in the name of efficiency I think the best bet is to go with a board that uses a mobile chipset and use the M.2 slot like @Manderis has said. Or using the M4 Mac Mini with Thunderbolt expansion... though I suspect at that point you may be putting more power into your drives than the CPU/SoC if you have more than a few HDDs. So you may have to consider denser drives that are more expensive whose ROI could be measured in decades rather than years.

[geoffro]

How reasonable is the idea of using a raspberry pi? How minimal could one go I wonder?

[Manderis]

You can go Pi but not with Hexos/TrueNAS. There is no Arm support. 

I have seen a Zimaboard solution on this forum though. 

[Mobius]

$4/kw makes sense electricity costs are insane i don't remember the exact but I'm pretty sure my cost is somewhere between 0.38¢ - 0.48¢/w

So power efficiency is hella sexy

 

Things i kept in mind are

1) no rgb

2) no dgpu

3) external das will likely use more power than internal drives and possibly have other issues

4) Wolfgang has a spreadsheet with psu efficiency and 20/40/60/80w so you can make sure you have a decently efficient psu at idle 

5) try not to go overboard with case fans, just because there is space for it doesn't mean it's needed. 

 

[frantiseksram]

I've been also looking into this. I got old i7 7700k CPU with gaming motherboard at my disposal die to PC upgrades, but worried it won't be economical on idle. I've seen the spreadsheet with low idle draw, but they are all on Fujitsu motherboards. What's the trick there? Also which one is right for my CPU? There seems to be a lack of official info on those motherboards out there. They are also using some other PSU, not your ATX kind, like I know from gaming. Would love to know more about those components, and why they are chosen most of the time.

[Manderis]

At some point you come into the realm of PSU low power efficiency. 

If you have one that is sized for a gaming pc you have a real influence. I grabbed the first unit seasonic 80+ gold from ltt labs

https://www.lttlabs.com/articles/psu/seasonic-focus-gx-850-atx-3-2024

In a low power scenario you have ~66% efficiency. So I only can imagine having a system tailored to run under load sub 50 W and idle under 20 W has its benefits.

The OEM motherboards are all something of a wild card. From the one German overview list the i5-9500t on a hp oem board has idle power of 1,5 Watt and load 63 Watt. That is really impressive. So you can get the performance if you need it. 

I am looking to pick up a hp elitedesk 800 g5 i5-9500t from ebay for ~200 €. I already asked a friend for a power meter so I can play around with different configurations and bios settings to get idle as low as possible. I will share my results with the forum if there is any interest. 

For me I just have to save 20 W idle and I save around 50 €/Year. So after 4 years my cost over a "free" pc that is sitting in the basement is amortized. And I have not even touched the topic of noise if you don't have to get rid off the heat. My hope is to get the system semi passive (cpu fan curve high temp activation only) and install the a single 120/140 mm noctua or similarly silent fan somewhere Frankenstein on the case which handles all the heat. 

 

I am also a bit concerned regarding HDD idle use of ~6 W. But two or even three 4 TB SSD is just not cost effective. 

[jorceshaman]

On 12/7/2024 at 2:38 PM, Mobius said:

$4/kw makes sense electricity costs are insane i don't remember the exact but I'm pretty sure my cost is somewhere between 0.38¢ - 0.48¢/w

So power efficiency is hella sexy

 

Things i kept in mind are

1) no rgb

2) no dgpu

3) external das will likely use more power than internal drives and possibly have other issues

4) Wolfgang has a spreadsheet with psu efficiency and 20/40/60/80w so you can make sure you have a decently efficient psu at idle 

5) try not to go overboard with case fans, just because there is space for it doesn't mean it's needed. 

 

Specifically points 1 and 5, I'm hoping to be able to disable some RGB that came with some of my components. And Probably unplug 2/4 of the included case fans, just leaving 1 in the front and 1 in the back.

[mggevaer]

Thanks for all the ideas people. I' not looking for very high performance at the moment, so it looks like something with a mobile chipset is the way to go.

[Manderis]

I got the Elitedesk with the 9500t and 2x 4 tb WD Red Pro's (7200 rpm) are on the way. 

I can borrow a power measuring plug around Christmas. So I hope to be able to optimize the power consumption. I was positively supprised by HP's use of a 250 W 80+ Platinum PSU. 

Fingers crossed that I get below 20 W in idle. 

Be aware that you will have trouble installing more than 2x 3.5" drives in any HP SFF case, this will probably be true for similar Lenovo or Dell models. I think I can dremel the 2.5" bay away and print something if I want to. For know I am fine with 2 drives plus Sata SSD. 

I am locking myself in a two drive scenario a bit but I hope that maybe hexos will support expanding 2 drive mirrors one day. And 4 TB is fine for me for some time. When the time comes I will either modify the case or print a new one.