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Power supply maths help

james8449834
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1 hour ago, brob said:

 

Hopefully my arithmetic is correct 🙂

 

Cost per Wh: £0.247 kWh / 1000 = £0.000247

 

Given a consistent draw from PSU of 400W @ £0.000247 Wh

 

Estimated from https://en.m.wikipedia.org/wiki/80_Plus 230V non redundant:

~91% efficiency with 850W 80+ Gold = ~439.56W

~93% efficiency with 1000W 80+ Platinum = ~430.11W

 

Difference 439.56W - 430.11 = 9.45W

Cost saving 9.45 * 0.000247 = £0.00233415 per hour

 

£20 cost recovered after ~8,568 hours.

Thank you that is exactly what I wanted to know, got my head around power supplies, one more thing to decide and I can order the dam thing 

Posted

I'm browsing for power supply I know what wattage in need and all that good stuff. 

 

I'm just trying to work out how long it will take to recover the extra spend if I get a more efficient,

 

Is there a cost per killer what how over effectively times by efficiency formula 

 

The more efficient one is also 1000w and I only need 850w so getting the more expensive one would give me head room for upgrading so I would potentially get more use but I just want to work out the timeframe 

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2 minutes ago, james8449834 said:

I'm browsing for power supply I know what wattage in need and all that good stuff. 

 

I'm just trying to work out how long it will take to recover the extra spend if I get a more efficient,

 

Is there a cost per killer what how over effectively times by efficiency formula 

 

The more efficient one is also 1000w and I only need 850w so getting the more expensive one would give me head room for upgrading so I would potentially get more use but I just want to work out the timeframe 

Whats a 'killer what'? 

In all seriousness, it all depends on how much you use your system, how you use your system and how much you pay for electricity.

It also depends on the price of the unit vs the other one.

Maybe you save a couple of cents a month?

 

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3 minutes ago, Hinjima said:

Whats a 'killer what'? 

Took me a second, but "kilowatt".

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10 minutes ago, james8449834 said:

I'm just trying to work out how long it will take to recover the extra spend if I get a more efficient,

Do you run your PC under full load 24/7, running something like a distributed computing project like some of us crazy madmen do?

 

If yes, yes. It will be worth it.

 

If no, no. You won't run enough electricity to justify going from Gold to Plat / Tit.

Want to help researchers improve the lives on millions of people with just your computer? Then join World Community Grid distributed computing, and start helping the world to solve it's most difficult problems!

 

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24 minutes ago, Hinjima said:

Whats a 'killer what'? 

Believe it or not, several things.

I (for the fun of it googled it and hoped for an electron with a knife) and turns out it is everything from a rock band to video games and table top games to IRL criminals has in some way been named a killer what/watt

I edit my posts for so if you saw a typo.... no you didn't, you are just crazy
 

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1 hour ago, james8449834 said:

I'm browsing for power supply I know what wattage in need and all that good stuff. 

 

I'm just trying to work out how long it will take to recover the extra spend if I get a more efficient,

 

Is there a cost per killer what how over effectively times by efficiency formula 

 

The more efficient one is also 1000w and I only need 850w so getting the more expensive one would give me head room for upgrading so I would potentially get more use but I just want to work out the timeframe 

what model power supply are you looking at?

proud owner of a AMD Athlon 64 cpu

PSU tier list: https://docs.google.com/spreadsheets/d/1akCHL7Vhzk_EhrpIGkz8zTEvYfLDcaSpZRB6Xt6JWkc/edit?gid=1973454078#gid=1973454078

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Posted

What I recommend is, add up the wattage everything needs and get the next largest size of PSU for overhead when you change or add components of if you're planning on upgrading and are starting with a base system so that you heave something usable today.

 

For example, if everything adds up to 320 Watts get one rated at 350 Watt, there is no real benefit gained from getting anything much bigger, UNLESS the cost is the same or lower for the same or better standard rating.

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Posted (edited)
1 hour ago, Thomas53 said:

For example, if everything adds up to 320 Watts get one rated at 350 Watt

I think that's a bad rule.

For example my system RTX3070(undervolted) + intel 12400 + extra = 200+70+50 W

So I buy a 350W PSU ?

I have a 550W psu (which is already considered tight) and I wouldn't feel safe with a 350W.

A 350W psu won't even be able to power my GPU, no two available 8pin pcie power connectors.

Also consider most psu efficiency curves are peaking at midload.

Edited by leclod

If you don't quote us, we won't know you answered

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2 hours ago, Millios said:

Believe it or not, several things.

I (for the fun of it googled it and hoped for an electron with a knife) and turns out it is everything from a rock band to video games and table top games to IRL criminals has in some way been named a killer what/watt

There are killer whales tho 😄 

 

Back to topic, a better build PSU will also last longer

But for a given build quality buying a PSU above requirements is just a loss - but it offers possibly better upgrade path, as PSUs last for longer than core components (CPU, GPU..)

AMD R9  7950X3D CPU/ Asus ROG STRIX X670E-E board/ 2x32GB G-Skill Trident Z Neo 6000CL30 RAM / ASUS TUF Gaming AMD Radeon RX 7900 XTX OC Edition GPU/ Phanteks P600S case /  Arctic Liquid Freezer III 360 ARGB cooler/  2TB WD SN850 NVme + 2TB Crucial T500  NVme  + 4TB Toshiba X300 HDD / Corsair RM850x PSU/ Alienware AW3420DW 34" 120Hz 3440x1440p monitor / ASUS ROG AZOTH keyboard/ Logitech G PRO X Superlight mouse / Audeze Maxwell headphones

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Most hobbyist desktops spend the bulk of time drawing under 20% of PSU capacity.

 

Unless electricity is prohibitively expensive the price premium demanded of very high efficiency PSU makes cost recovery unlikely.

 

Like many PC components pricing is very much reflective of demand. It's hard to find a quality PSU < 500W and units around 750W - 850W seem to have better pricing.

80+ ratings certify electrical efficiency. Not quality.

 

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5 hours ago, Hinjima said:

Whats a 'killer what'? 

In all seriousness, it all depends on how much you use your system, how you use your system and how much you pay for electricity.

It also depends on the price of the unit vs the other one.

Maybe you save a couple of cents a month?

 

Thanks I'm not going to apologize for dyslexia.

 

But let's say for the sake of augment it's 4 hours a day and I'm doing a task the means the system is consuming a consistent 400w of power 

 

Power supply a is an 850w gold 

Power supply b is an 1000w platinum 

 

B costs £20  

 

And power costs £0.2470 per kWh 

 

 

 

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53 minutes ago, james8449834 said:

Thanks I'm not going to apologize for dyslexia.

Absolutely not!  I have my own issues.  Just a bit of fun, dont take it too serious 🙂 

53 minutes ago, james8449834 said:

 

But let's say for the sake of augment it's 4 hours a day and I'm doing a task the means the system is consuming a consistent 400w of power 

 

Power supply a is an 850w gold 

Power supply b is an 1000w platinum 

 

B costs £20  

 

And power costs £0.2470 per kWh 

 

 

 

You might make back that 20 bucks after a year or two.

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43 minutes ago, james8449834 said:

Thanks I'm not going to apologize for dyslexia.

 

But let's say for the sake of augment it's 4 hours a day and I'm doing a task the means the system is consuming a consistent 400w of power 

 

Power supply a is an 850w gold 

Power supply b is an 1000w platinum 

 

B costs £20  

 

And power costs £0.2470 per kWh 

 

 

 

 

Hopefully my arithmetic is correct 🙂

 

Cost per Wh: £0.247 kWh / 1000 = £0.000247

 

Given a consistent draw from PSU of 400W @ £0.000247 Wh

 

Estimated from https://en.m.wikipedia.org/wiki/80_Plus 230V non redundant:

~91% efficiency with 850W 80+ Gold = ~439.56W

~93% efficiency with 1000W 80+ Platinum = ~430.11W

 

Difference 439.56W - 430.11 = 9.45W

Cost saving 9.45 * 0.000247 = £0.00233415 per hour

 

£20 cost recovered after ~8,568 hours.

80+ ratings certify electrical efficiency. Not quality.

 

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1 hour ago, brob said:

 

Hopefully my arithmetic is correct 🙂

 

Cost per Wh: £0.247 kWh / 1000 = £0.000247

 

Given a consistent draw from PSU of 400W @ £0.000247 Wh

 

Estimated from https://en.m.wikipedia.org/wiki/80_Plus 230V non redundant:

~91% efficiency with 850W 80+ Gold = ~439.56W

~93% efficiency with 1000W 80+ Platinum = ~430.11W

 

Difference 439.56W - 430.11 = 9.45W

Cost saving 9.45 * 0.000247 = £0.00233415 per hour

 

£20 cost recovered after ~8,568 hours.

Thank you that is exactly what I wanted to know, got my head around power supplies, one more thing to decide and I can order the dam thing 

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On 6/4/2025 at 10:58 PM, james8449834 said:

Thank you that is exactly what I wanted to know, got my head around power supplies, one more thing to decide and I can order the dam thing 

Don't choose PSUs based on their efficiency. Choose them based on more meaningful things like their performance, noise, cables, and other nice to haves (cable pinouts, cable flexibility, lack of in cable capacitors, design etc)

:)

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12 hours ago, seon123 said:

Don't choose PSUs based on their efficiency. Choose them based on more meaningful things like their performance, noise, cables, and other nice to haves (cable pinouts, cable flexibility, lack of in cable capacitors, design etc)

Totally its creative accounting and on all honesty I had thought the there was a significant difference between the various ratings 

 

 

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