My 1993 IBM PS/1 was one of the first 486 computers to have Energy saving mode in bios.
Later after 1995 it became mainstream to have Energy saving mode in bios of most personal computers
With a CF card or SSD Sleep and Hibernation mode works fine.

I faced a similar issue where my older devices were noticeably increasing my energy bills. My first step was to upgrade to more energy-efficient models where feasible. This initially seemed like a big investment, but it paid off in the long run with lower energy bills and better performance.

In the interim, while I still had some old hardware, I made adjustments to reduce their energy drain. I actively used power-saving modes and was careful about shutting them down when not in use. This helped to some extent in managing the consumption.

Additionally, I discovered a useful resource at https://thingsboard.io/smart-energy/, which provided smart-energy solutions. Their platform offered efficient monitoring and management of energy usage, including features like real-time data visualization and advanced data processing. This gave me insights into my energy consumption patterns and helped me make informed decisions to reduce my energy usage further.

When you get a dual X5365 system with 64Gb of Fully Buffered DIMMs a n 8800 Ultra and 4 15k RPM disks you realise just how energy efficient those old computers really are.

ElectroSoldier wrote on 2023-11-18, 13:19:

When you get a dual X5365 system with 64Gb of Fully Buffered DIMMs a n 8800 Ultra and 4 15k RPM disks you realise just how energy efficient those old computers really are.

🤣 yeah probably runs about 250 watts at idle desktop. My XP box runs 180 watts at idle desktop (q9650 with 3 hds and 8800gt) according to the smart ups panel, so never leave it on unless in use. It's BIOS has near 0 power saving features.
My i7-8700k box runs 45watts at idle.....

My 486 have power setting in the BIOS but all are set to disabled because it cause issue (screen blanking after x minutes : screen turn off then on when i'm playing retro games while other option like hdd timeout are not that useful when you are using CF card.)

So as a first way, I would say to switch to CF or SD card if it's not already done, because that's power saved in any case and theses solutions are all better than rotating rust solution.
Switching the power supply for a more efficient, while it work to lower consumption, won't provide any other benefit.

Personally, I don't care much, I'm totally off-grid as far as energy go.

And if I get a rare "5 days of clouds event", then i am more likely to do gaming on my 486 instead of the Ryzen + radeon system because the 486 use a lot less power.

More like 310-350w at idle.
I hardly ever use it these days, Its my Ultimate Windows 2000 build.

With energy costs they way they are in the UK it costs about 11pence at hour while idle.

I have a Skylake based system that can run idle all day and cost that much, Coffee lake adds some improvements but not much.

My current retro computer has a VIA C3 CPU which are focused on lower power consumption and a GeForce2 GTS card that doesn't use much energy. However, it is connected to a CRT monitor (just like it was back then, and it is the only one that I currently have) which aren't efficient compared to the LCD ones.

Modern hardware has throttling capabilities that weren't present with older ones to avoid wasting unnecessary energy, particularly when running idle or not doing any heavy stuff.

I've never really had issues with this and I"ve been running sometimes up to six or more "Retro-Pcs" all day long 24/7/365 in a networked setting since 2002. Most of these machines have power supplies that will never breech 300 Watts - and most modern systems, especially those made for gaming,; have 500 watts or more. Sure, it does add a LITTLE - and that will add up - but for most people, the price is pretty inconsequential compared to say, running your HVAC all day and all night.

Actually, funny story, in my single years in the 2000's, in my 1st apartment, I used to run my 8088-80486 machines in the winter time all day and all night to keep the apartment warm. That combined with leeching off the neighbors cooling really kept my power bill down. I've lived in the most expensive parts of the country (Seattle) and my power bill even with a 286, 386, 486, i1400 ThinkPad, ThinkPad 755CD, an old BLX2 Blue Lightning, a Power Mac 6400/180....and god only knows what else all running at one, some 24/7/362ish - and I never had a power bill over $115 bux, with an average of $75 or under even in the winter usually ($115 usually was when I started running power tools to build guitars or using the CRT TV a lot). I don't think I ever used my heater the entire time I lived there.