My computer eats about 350W on full load (RX 580, Ryzen 5 1600). Many PSU calculators suggest me bronze 650W - 700W PSUs. This is because in order to reach maximum efficiency we need to use about 50% of what our PSU can output. But... does it really matter?
A 80 Plus Bronze PSU, which is the most common type, will give:
- an 82% efficiency under 25% load;
- an 85% efficiency under 50% load;
- an 82% efficiency under 75-100% load.
We can see that our efficiency changes very little, only about 3%, on all possible loads, from 25% to 100%.
Now, taking my pc as a point of reference, let's equip it with a 700W PSU, which will result in a 50% load. Our efficiency will be about 85%, which means our PSU would draw 350W / 85 * 100 = 411W from the wall.
Let's give my pc a 450W PSU, which will result in a 75% load (slightly more than that). Our efficiency will be about 82%, which means our PSU would draw 350W / 82 * 100 = 426W from the wall.
That's a 15W difference. Where I live, we pay 0.24€ per KiloWatt hour. If I used my pc 5 hours a day, every day UNDER FULL LOAD (which is very unlikely) I would pay 15W * 5 * 365 / 1000 * 0.24€ = 6.57€ more per year, or 7.75$ for you American folks.
Conclusion: is it really worth spending 30-40€ more for a more powerful PSU, that can always stay at maximum efficiency?
I'd like to know your opinions.