cloudberries
From what I understand, PSU's run best at 60-80% of their labelled Wattage. Does it make sense to calculate the maximum wattage and then mark it up in accordance with this? Or will that lead to me buying an overkill PSU?
 
It's been a while since I built a PC and this is one of the areas I am least confident about. Thanks!

It's a 2-3% difference between 75% and full capacity, the % load is meaningless.
 
You need about 50-100w headroom over your maximum theoretical power output to be safe, that's what matters.

ty_ger07
If you buy a good Titanium rated power supply, I agree with what is said above. The difference in efficiency between 70% load and 90% load is almost immeasurable with a Titanium rated power supply; and there is no need to go overkill with the wattage rating, since computer component efficiency is getting better and better, and if you don't need a 1000 watt power supply right now, you probably won't need one in 2 years either.

It's only the crappy lower-end 80-plus power supplies which benefit quite greatly in efficiency by going overkill.

So getting a better Grade (like platinum) will mean you dont need the overhead that a 80-gold or something would?

I agree with everything said here. I only use Titanium rated units. They last longer, are more efficient, but cost more. I rarely get one under 1000W, but any unit you buy should be based on what your system pulls.

I would also suggest that you get a UPS (Uninterruptible Power Source) which regulates the power into your PSU and also allows you to shut down and save if you have a brown out or if there is a power failure. These devices also help your PSU last longer and help your components because the power is much cleaner than what comes directly out of your wall.

ty_ger07
If you buy a good Titanium rated power supply, I agree with what is said above. The difference in efficiency between 70% load and 90% load is almost immeasurable with a Titanium rated power supply; and there is no need to go overkill with the wattage rating, since computer component efficiency is getting better and better, and if you don't need a 1000 watt power supply right now, you probably won't need one in 2 years either. The 80-plus Titanium 650 watt power supply I am using right now is only about 50 to 100 watts more than I need, and upgrading to it from a 1200 watt 80-plus gold made a significant difference in my power use -- particularly at low loads (since 80-plus gold and lower efficiency tapers off a lot at low loads).

It's only the crappy lower-end 80-plus power supplies which benefit quite greatly in efficiency by going overkill.

Titanium does sound generally better then, a slightly higher initial cost for more efficiency would definitely be preferable for me. Also, I hadn't even considered the noise level, but quiet/silent always seems good!

150-200w above and more for higher efficiency if possible

LucasShearer

ty_ger07
If you buy a good Titanium rated power supply, I agree with what is said above. The difference in efficiency between 70% load and 90% load is almost immeasurable with a Titanium rated power supply; and there is no need to go overkill with the wattage rating, since computer component efficiency is getting better and better, and if you don't need a 1000 watt power supply right now, you probably won't need one in 2 years either.

It's only the crappy lower-end 80-plus power supplies which benefit quite greatly in efficiency by going overkill.

So getting a better Grade (like platinum) will mean you dont need the overhead that a 80-gold or something would?

No. A decent bronze, gold, platinum, or titanium will all put out their rated wattage at their rated temperatures. If they are rated for 650w, they should all put out 650w, but some might do a little more, or slightly less. The difference is that it will take a gold rated PSU around 575 watts from the wall to give your PC 500 watts. Since platinum/titanium are 3% more efficient, it will take around 556 watts from the wall to give your pc 500 watts. Most PC's average much less than 500 watts so that 19 watts is high, and it will most likely be less than .2's cent an hour in electricity.  At 13 cents for 1000 watts each hour (average in USA) saving 10-20 watts is nothing (1/10th-2/10th a penny an hour).   Where titanium shines is it can be more efficient outside those 20-80% loads. It's tech that should trickle down, but is about it's only feature/selling point for that tier. Gold is already pretty great at 87%+, and platinum would then be Titanium if they made them efficient through the whole range.
 
Gold is generally all any gamer needs unless electricity is super expensive where you live, and/or you are running your rig hard, 24/7, like a server. Platinum is usually upsold with nicer cables, and warranty since 3% is nothing really. As much as I like titanium features, I'd only invest in it if I had a high powered system that ran below 20% for long periods (I prefer to shut down my machines when not in use, good for the environment, and my electricity bill), or I needed to push past 80% for extended periods, and couldn't just buy a larger gold, or platinum to keep it below 80%.
 
 

JSohn

LucasShearer

ty_ger07
If you buy a good Titanium rated power supply, I agree with what is said above. The difference in efficiency between 70% load and 90% load is almost immeasurable with a Titanium rated power supply; and there is no need to go overkill with the wattage rating, since computer component efficiency is getting better and better, and if you don't need a 1000 watt power supply right now, you probably won't need one in 2 years either.

It's only the crappy lower-end 80-plus power supplies which benefit quite greatly in efficiency by going overkill.

So getting a better Grade (like platinum) will mean you dont need the overhead that a 80-gold or something would?

No. A decent bronze, gold, platinum, or titanium will all put out their rated wattage at their rated temperatures. If they are rated for 650w, they should all put out 650w, but some might do a little more, or slightly less. The difference is that it will take a gold rated PSU around 575 watts from the wall to give your PC 500 watts. Since platinum/titanium are 3% more efficient, it will take around 556 watts from the wall to give your pc 500 watts. Most PC's average much less than 500 watts so that 19 watts is high, and it will most likely be less than .2's cent an hour in electricity.  At 13 cents for 1000 watts each hour (average in USA) saving 10-20 watts is nothing (1/10th-2/10th a penny an hour).   Where titanium shines is it can be more efficient outside those 20-80% loads. It's tech that should trickle down, but is about it's only feature/selling point for that tier. Gold is already pretty great at 87%+, and platinum would then be Titanium if they made them efficient through the whole range.
 
Gold is generally all any gamer needs unless electricity is super expensive where you live, and/or you are running your rig hard, 24/7, like a server. Platinum is usually upsold with nicer cables, and warranty since 3% is nothing really. As much as I like titanium features, I'd only invest in it if I had a high powered system that ran below 20% for long periods (I prefer to shut down my machines when not in use, good for the environment, and my electricity bill), or I needed to push past 80% for extended periods, and couldn't just buy a larger gold, or platinum to keep it below 80%.
 
 

My point is that the reasons people go overkill with lower-rated power supplies are no longer valid if you buy a titanium power supply. 1) With a lower-rated power supply, they create more wasted heat, and people go overkill to reduce the heat and extend the lifetime. 2) With a lower-rated power supply, efficiency drops off at the high end of their rating, so people go overkill to stay in the efficient part of the curve under heavy load (but then they are again inefficient at low loads of their over-rated power supply). Both of those reasons become invalid with a titanium power supply. So, with a titanium, there is less reason to go overkill.

JSohn
Pro tip: Learn about undervolting. You can get much better temps, a mild OC, use noticeably less power, and possibly get by with a smaller power unit if you measure things out. It's win/win. It's free, and doesn't take long to learn the basics. One afternoon of tweaking can save you money, and get you better performance. In general 450 watts are plenty for most gaming systems. Since quality 500-600 watt units go on sale for the same price, I usually go bigger if price is close. My old ITX build ran a 1080 ti, i7 with an SFX 460w unit. No issues. 
 
Pro tip 2: Buy a kill-a-watt to measure the actual power from the wall. I've never heard any noobie say they were pulling more than they thought they were. They are always surprised how much less their rigs are actually pulling. See my post above if you don't the difference between how much power your PC is using, and how much the PSU is pulling from the wall.

I am doing both of those pro tips (and more [.. duration power limits and power plane power limits, etcetera]), and I found that my 600 watt titanium is better than the 1200 watt gold I was using previously.  Do what you want, but don't just say that I am wrong.
 
In my instance, I was peaking out at around 500 to 550 watts, and with my previous 1200 watt gold PSU, the efficiency was fine for max load, but then, while surfing the web, I was running down at miserable efficiency.  You can't simply turn your computer off at low loads.  What if you are using your PC at low load?  That was my point.  People needlessly buy an excessively high wattage lower-efficiency PSU for the reasons I mentioned, and then they sacrifice low-load efficiency, high load heat, and the price of the excessive-wattage PSU that they didn't really need.  If you buy a lower efficiency PSU, you force yourself to buy a higher wattage PSU, and then whenever you operate your computer for lower-power loads, you are running it where it isn't efficient.  Or, if you instead size that lower-efficiency PSU to run efficiently at medium loads, then it is inefficient at high loads and may overheat and shut off at high loads due to all the excess heat it inefficiently creates at high loads.  You have to play this game of sizing the PSU just right to fit your needs.  What if there was an easier way?!
 
From the price perspective, I don't think that you are taking into account how much extra wattage people are deciding on and how much extra that greater wattage rating adds to the cost.
 
Let's look at the numbers:
If you have a system which NEEDS 500 watts, without using a kill-a-watt meter, people often overestimate what their system will need as a matter of caution, and believe that they use 600 or 700 watts.  Then, they buy a 1000 watt Gold PSU to extend its life and increase its high-load efficiency; as so often recommended, and the reason for this thread.  A decent 1000 watt gold PSU costs around $200 to $250.
On the other hand, if you are like me, you measure your system's actual load, you determine that it peaks at around 500 watts, and then you realize that a 600 or 650 watt titanium is plenty and offers the benefits described.  How much does it cost?  Around $200 to $250.
 
Same cost.  Better efficiency under every circumstance.  Less heat.
 
If you are buying a PSU, it's something you should take into consideration instead of mindlessly buying a big gold PSU which is 40% or 50% higher wattage rating than what you need.
 

Titanium is great because they are almost 100% efficient below 20% loads, and 80+ efficient above 80% loads to near 100% loads.

Huh?  You mean 90%+ efficient?  A titanium PSU is 90%+ efficient from 10% load to 100% load.
 
 
 
Before, I was surfing the web and watching videos at about 73% efficiency.  Now I am doing the same at about 92% efficiency.  I sold my old PSU, got a better PSU, and I don't regret any of it.  I am not saying that people have to do this, but I am saying that it is something you should consider instead of mindlessly following the 40% to 50% excessive wattage recommendation without considering the reasons that recommendation is being made and how those reasons may be invalid or circumvented by a same-price higher-efficiency smaller power supply.
 
The OP's question was how much excessive wattage rating is needed.  In my opinion, with a high-efficiency PSU, not much excessive wattage rating is needed at all; and you end up with the same computer usability for about the same price and gain the benefits reduced electricity usage and reduced heat and noise.
 
The question was "How far above calculated Wattage should the PSU be?", and before answering that question, you need to carefully consider WHY so many people recommend a Gold PSU which is 40% to 50% greater in wattage than what your computer needs.  Once you have determined the "WHY", you consider alternatives which solve the same problems.  Then you compare prices.  Then you compare long-term benefits.  And you ask yourself, "Is there a better solution which few people have chosen in the past?" (probably because it wasn't always a cost-effective option).

I've personally have around a 100w headroom and if you're overclocking, maybe a 150 - 200w headroom just in case so you can do some good overclocks.

ty_ger07
Correct.
A higher efficiency power supply means that it will be more efficient over a wider range of loads, and it will create less wasted heat. Both of those factors mean that you won't need as much overkill, or the primary reasons overkill is recommended are no longer valid.
 
Put it this way: with everything else in my computer being the same, I upgraded from a 1200 watt 80-plus Gold to a 650 watt 80-plus Titanium, and I consider it a definite upgrade.  The 650 watt Titanium is quieter (actually, fan-less and silent!), efficiency is measurably better over the full range (but especially while browsing the web/idling), it is smaller, it is cooler, and it has worked flawlessly even though it is much closer to being barely adequate for my theoretical max power consumption.

What is this power supply you have, and how much did you pay for it? I'm gifting a build that should never need more than 500W.

Beanard

ty_ger07
Correct.
A higher efficiency power supply means that it will be more efficient over a wider range of loads, and it will create less wasted heat. Both of those factors mean that you won't need as much overkill, or the primary reasons overkill is recommended are no longer valid.
 
Put it this way: with everything else in my computer being the same, I upgraded from a 1200 watt 80-plus Gold to a 650 watt 80-plus Titanium, and I consider it a definite upgrade.  The 650 watt Titanium is quieter (actually, fan-less and silent!), efficiency is measurably better over the full range (but especially while browsing the web/idling), it is smaller, it is cooler, and it has worked flawlessly even though it is much closer to being barely adequate for my theoretical max power consumption.

What is this power supply you have, and how much did you pay for it? I'm gifting a build that should never need more than 500W.

Seasonic PRIME Titanium 600W Fanless
You can find it at select locations for about $210 right now.

after reading most of the posts here, its pretty informative 
 
but i should also mention that anyone should just buy the best equipment they can get their hands on, if their budget allows it, Titanium rated units are expensive, personally i'd just go for Gold simply because my budgets are low
 
so u have money to spend, Titanium are more efficient (220v input)
 
u can find an article on Tom's hardware about PSU ratings