So this may be a stupid and self evident question…but if you have a say, 750 watt PSU - is that the maximum your computer could possibly consume?
I know, I know…a bit of a “Who’s buried in Grant’s Tomb…?” question…
I’m trying to remember if I have a utility that would show total system wattage consumed in real time. I think there might be one for my GPU…but not the whole system… I’d love to see what it does with various high end graphics programs…
Hmm…might be a hardware thing that can measure it…
It’s more as a guide to plan for ‘peak load’ rather than normal use. Modern PC motherboards have about six stages of power saving, so the ‘crank up’ load is often very different from the ‘ticking over’ power draw. The best thing to do is put in your hardware and then you’ll see a load guide on something like this:
This one also does it in watts per day:
Most people tend to over-spec PSU’s as there used to be a strong correlation with quality and cost, so even though they only needed 400 watts peak draw, they’d buy a 750 because it is a higher end make. This can be little inefficient (literally, PSUs have an ‘efficiency’ rating), but it is not like the 750 is drawing at capacity anyway - it generally draws just watt it needs 
People also tend to ‘what if’ a lot on PSUs, in that you might only run one GPU but there is always the nagging suspicion that a good quality 500w won’t cut it for having those dual TitanX’s…
I’m lucky enough. to have two fast PC’s for flight sim and high end gaming stuff, so boot them up a couple of time a week perhaps?
Apart from that, a good lappy and also an I7 2600 with GTX780 in my hobby room I probably use the most.
As for my dedicated Sim PC’s, I’ll fire them up and check for OS updates, little bit of preliminary ccleanewr maintenance, check for patches, on SSD’s so no need for defrag, then reboot to be sure for a dedicated sim session )
It works for me.
Just reading what you typed there Fearless, agree with most of what you say but as regards PSU’s, its not down to the wattage, its down to the quality of the PSU itself, sure calculate your wattage usage but pleases also calculate the quality of a good PSU … a good PSU and perhaps a good case can see you through dozens of upgrades and I’ve always considered these two items as a solid foundation for a good PC build that can last a few generations of PC Builds.
A bad quality PSU regardless of wattage can take out a whole PC hardware components when it blows, I’ve repaired many a scenario.
As regards calculating PSU power consumption in its self, remember too all things degrade and PSU’s are no exception, so for a guaranteed 1000W PSU, that might be 10% less efficiency in its warranty, and yes that deterioration can be measured.
I do a bit of IT and mostly fixing PC’s for friends and family here and its shocking the corners they want to cut sometimes and trying to steer them from bad habits.