I'm using 1 of the EVGA 1600W PSUs in this computer (2700k) and the most wattage this box would probably ever use is around 600W - or at least it will be when i get the GPU i RMA'd back from MSI. So it's definitely overkill. Could've saved $150 by getting the 1000W version, but at least this way i'm covered if the upgrade bug bites me really hard. In a way i guess it's sort of future-proofing.
Out of curiosity, let's have fun with some math
Corsair CX 850m = $100 (it is currently on sale at Newegg. Normal is $120. We'll go with the lower price just to give Corsair an advantage. We'll also assume it stays on sale for the 10-year duration of this scenario.)
EVGA SuperNova 1000W T2 = $280 (not on sale)
Let's assume we were going to use each of those PSUs in my 2700K box and i had both GPUs installed and crunching so it was drawing the 600W. Let's also assume i'm paying the national avg. of $0.12 kW/h for electricity. We'll also assume both PSUs die on the day their warranty runs out, and the cost of the PSUs and the cost of electricity do not increase during this time. We'll also assume there are no issues with either PSU during the warranty period, and therefore no RMAs.
With a 600W load, the Corsair CX 850m would be at 71% capacity, bringing efficiency to 84%. The EVGA SuperNvoa 1000W T2 would be at 60% capacity, bringing efficiency to 94%.
This means power draw at the wall would be...
Corsair CX 850m: 715W
EVGA SuperNova 1000W T2: 639W
For a difference of 76W. So, running both for an hour equates to a waste of 0.076 kW/h using the Corsair = 1.824 kW/h/day = $0.21888 wasted per day.
Total wasted electricity after 10 years = $799.35
Now we factor in the cost of the PSUs. Since the Corsair's warranty is only half of EVGA's, you had to replace the Corsair during this 10 year period, adding an extra $100 to the cost of ownership, making your total cost of the Corsair $200 (assuming free shipping and no sales tax).
Cost of purchasing EVGA ($280) minus the cost of the Corsairs ($200) = $80
So your total loss after 10 years = $719.35 if you use the Corsair instead of the EVGA. Per computer.
Edit: The EVGA SuperNova 1000W T2 is on sale at Newegg right now for $250, so you'd actually save $749.35
Edit #2: Not everyone is lucky enough to pay $0.12 per kW/h, so here's another example:
In March 2016, the average rate was $0.213 in Los Angeles, meaning $0.3885 wasted per day, or $1418.85 wasted after 10 years per computer, by using the Corsair CX 850m instead of the EVGA SuperNova 1000W T2.
Last edited by John P. Myers; 04-28-16 at 06:05 AM.