SP20 PSU efficiency question

[xZork]

I know a modest amount about power supplies and how they can perform under load and would love some feedback. I have a limited amount of power that I can draw so efficiency is key. The way I see it I have 3 possibilities for powering this unit. My first though is buying a new (used) 1200 watt server PSU but I would rather not spend more than I have to since I have ATX PSU's laying around not being used. My options for what I have on hand are several Corsair 750's, one hx1050 and one dell server PSU rated @ 750 watts. Now what I am not sure about is how these possibilities will effect load on a circuit. Would buying a 1200 watt server PSU pull less than running two 750's? Then there is the questions of underclocking an running the 1050. Currently I have 2 ant S3+ units on the 1050 but I could spread those out if needed. I would assume that a single server PSU would be the best bet, but how much of a difference could it make. I am still running as many S1's as I can while I upgrade.

I had a kill-a-watt that I lent out and it was returned fried, kind of a long story I need to get a new one...

Thanks for reading!

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[sidehack]

Spreading across a pair of 750W, unless the PSUs are pretty tired and/or underperforming, will likely run more efficient than a single 1200W. Efficiency curves typically peak near the middle of the load range so you might squeak a percent or two out of it by loading down 1500W to the 2/3 point over loading 1200W to the 5/6 point.

[Syke]

Spreading across a pair of 750W, unless the PSUs are pretty tired and/or underperforming, will likely run more efficient than a single 1200W. Efficiency curves typically peak near the middle of the load range so you might squeak a percent or two out of it by loading down 1500W to the 2/3 point over loading 1200W to the 5/6 point.

Mostly true if they're all rated the same. If not, for example, 2x 750 Bronze PSUs will be less efficient than a single 1200 Gold PSU.

[xZork]

Spreading across a pair of 750W, unless the PSUs are pretty tired and/or underperforming, will likely run more efficient than a single 1200W. Efficiency curves typically peak near the middle of the load range so you might squeak a percent or two out of it by loading down 1500W to the 2/3 point over loading 1200W to the 5/6 point.

Mostly true if they're all rated the same. If not, for example, 2x 750 Bronze PSUs will be less efficient than a single 1200 Gold PSU.

These are CX750's and 750m so all bronze. If the difference is negligible then sticking with the pair of 750's would obviously be better, they are all right at a year old and if one did fail there are extras. I have zero knowledge of server PSU's and just assumed that if it was designed specifically for handling constant high load it might be worth it. I am not sure the standard server PSU's are rated and if the expenseis worth it. Basically asking if one way or another would allow me to keep running 1 more S1 or not. Trying to squeeze these things dry.

I guess a pair of 750's it is, and if there are any issues I may have to ask for more wisdom.

Thank you both for the replies!

[sidehack]

True, nominal efficiency ratings are important. A topped-out 1200W server PSU is probably more efficient than a bronze-rated PSU at its best possible operating point.

[Gamla]

I trust Corsair RM series, I have 2 x RM750, also Enermax Platimax series is good.