[SOLVED] low wattage rig and high wattage PSU

[Pextaxmx]

If I have a 550W and a 850W PSU from the same series (Focus GM) and want to use either in a basic IGPU system, which hardly reaches 100W, is there any disadvantage for using the bigger 850W PSU over the 550W one? What is the consequence of drawing sub 100W (even sub 50) from a 850W PSU for a year or two?

 

[sizzling]

At the extreme ends of usage (<10% and >90%) is where a psu is least efficient. So the 550w for example needs to be over 55w to be out of the bottom 10% and the 850w needs to be over 85w. However it’s not a big difference in efficiency. So although technically the 550w will be cheaper to run it’s a tiny insignificant difference. I had a quick look but didn’t find an efficiency graph for that psu so here is the general table, the 10% is blank at it can drop off in most ratings.

 

[Pextaxmx]

thank you for taking the time and answering the question so nicely. How about the stress level on the PSU? Would extremely low wattage use for prolonged period stress the 850W PSU more than the 550W one?

 

[helper800]

thank you for taking the time and answering the question so nicely. How about the stress level on the PSU? Would extremely low wattage use for prolonged period stress the 850W PSU more than the 550W one?

No. The higher the load (watts) the more stress on PSU components, and even then they can last years at 70%+ usage. Usually a good PSU will last through their warrantied period even at higher stress, constant load situations.