TJ Hooker :
@bit_user I understand where you're coming from, but like I said, even though wasted power as a percentage may be relatively high at low loads, in absolute terms it's quite low. Like 10W from my previous example.
Yes, 10W seems like a reasonable ballpark. My power costs me about $0.50 / kWh. If I leave that PC on 24/7, that's almost $4/month. And let's not forget that this is plugged into my UPS, which has its own inefficiencies. And, in the summer, I have to pay again, in order to remove the waste heat from that room via A/C or fans. But I don't pay for heat (it's included in my rent), so it doesn't help during the winter.
My PC probably idles somewhere in the neighborhood of 85 W, while its current PSU is 860 W (yeah, a little bit overkill). So, about 10%. But 80 Plus only specifies efficiency for 10% load for the Titanium level, so it could be worse than 80% efficiency @ 10% load.
Now, it so happens that PSU is a Seasonic Platinum model, and I'm definitely not replacing it just for the added efficiency of Titanium. However, if I were buying a new PSU, I'd tend to go for titanium unless doing so involved a tradeoff vs. performance or a significant price difference.
TBH, I don't leave that PC on 24/7, but it does sometimes stay on (and not sleeping) for days at a time.