Forum Thread

Power Supplies and electrical usage?

129 17 November 19, 2017 at 10:49 AM
HI All

I was going to build a computer for searching the web. I know all I need is a 350 watt supply but theres lots of sales on 500watt supplies. Is the electrical usage of a 500 watt supply that much greater over a 350 watt supply? I wont even be using a video card.

thanks

z

5 Comments

1

Sign up for a Slickdeals account to remove this ad.

This comment has been rated as unhelpful by Slickdeals users
Joined Oct 2004
L10: Grand Master
12,084 Posts
1,481 Reputation
#2
Nope you won't notice a difference.
Reply Helpful Comment? 0 0
This comment has been rated as unhelpful by Slickdeals users
Joined Dec 2015
L3: Novice
229 Posts
57 Reputation
#3
I've heard that having more headroom is more power efficient, but I don't have any data to back that up. I do know I have a much larger power supply than is necessary, and I sleep better. I don't like to stress power supplies; when they die, sometimes they take other components with them.
Reply Helpful Comment? 0 0
This comment has been rated as unhelpful by Slickdeals users
Joined Aug 2008
L99: Slicker than Ice
6,450 Posts
1,767 Reputation
#4
A 500W supply won't use 500W unless the computer needs it, and they tend to be most efficient in the 40-60% range, attached an efficiency curve of a PSU for example - they tend to be similar
Reply Helpful Comment? 0 0
This comment has been rated as unhelpful by Slickdeals users
Joined Jan 2016
L3: Novice
199 Posts
30 Reputation
#5
Any (decent) 400W - 600W supply will be fine.
Reply Helpful Comment? 0 0
This comment has been rated as unhelpful by Slickdeals users
Joined Feb 2004
L10: Grand Master
6,977 Posts
988 Reputation
#6
Quote from slapshot136
:
A 500W supply won't use 500W unless the computer needs it, and they tend to be most efficient in the 40-60% range, attached an efficiency curve of a PSU for example - they tend to be similar
Iagree

The PSU will only output the power that the computer is drawing. So, if the computer needs 150W, the PSU will only put out 150W, whether the supply is rated for 200W or 1200W.

What does change is how much power is drawn from the wall to get that 150W output. This is where the efficiency of the PSU comes in to play (and leads to those 80+ Bronze, etc ratings). If the PSU is 80% efficient, getting that 150W output takes 188W from the wall; if it's 90% efficient, it only takes 167W.

As the graph that slapshot posted shows, most PSUs have a peak efficiency when the load is about half of their max output. You can do all kinds of analysis to figure out how much power your computer draws during most of its usage, and get a PSU whose peak efficiency is in that range, but unless you've got a very power-hungry rig, it won't make much difference. That 150W usage is probably on the high end of the average (non-gaming) home computer, and the difference between 80% and 90% efficient PSUs is only 21W - about 0.5 kWh over the course of a day. And that's with a 10% difference in efficiency - the graph shows only a maximum 2-3% difference in efficiency of the PSU!

TL;DR, just grab a 500W PSU if that's what's on sale. The savings from the sale will be much greater than any savings you will see from carefully tuning your PSU to your computer's power needs.
Reply Helpful Comment? 0 0
Last edited by mmathis November 21, 2017 at 08:13 AM.
Marshall: Have the rest of you guys figured out by now that mmathis is the smartest guy on SlickDeals?
Page 1 of 1
1
Join the Conversation
Add a Comment
 
Copyright 1999 - 2018. Slickdeals, LLC. All Rights Reserved. Copyright / Infringement Policy  •  Privacy Policy  •  Terms of Service  •  Acceptable Use Policy (Rules)  •  Interest-Based Ads
Link Copied to Clipboard