What Happens If Your Power Supply Is Too Weak

While I was looking to upgrade my RAM and to add an SSD to my computer I had a thought that maybe the SSD would demand a lot more power from my power supply than it could output.  I have an HP Power PC 580-23W this PC has only a 300 watt power supply.  If I were to build this PC on my own it would need at least a 450 watt power supply.  So I was worried about what happens if I over tax my Power Supply and what that could lead to so here is what I found.

First adding an SSD and extra RAM barely needs any extra maybe 7 watts for both combined.

What Is A Power Supply

A power supply converts the Alternating Current (AC) from the electrical grid to Direct Current (DC).

First there was Direct Current in the simplest of terms DC flows in one direction doing work in that flow.  This used to be the standard for electricity but required a lot of power, incurred a heavy loss over distances and required large carrying wires for the transmission of electricity.

Along came Nicola Tesla (not the electric car maker) he was a true genius who saw the world in a very different way.  He was eccentric as well and his story is very fascinating, but he came up with Alternating Current where instead of one constant flow in one direction instead he devised a system where the electricity would work in a push and pull fashion doing the same work.  This led to the current power system we have since it requires less electricity to transmit power, smaller wires and while it does incur some loss over distances it doesn’t suffer as much as DC.

Now this is my rudimentary understanding of this I was never much for electrical studies.  Never was one of my focuses in school.

Now AC, while great for transmission, it sadly is not what most devices and components need so they need a converter that converts AC to DC this is what your power supply does and that giant power brick for your lap top do.  Almost any device has a AC/DC converter it is either internal or external.

Component Power Needs

Every component needs some electricity to function some like SSDs and RAM only need 1 to 5 watts where as other components like high end graphics cards need hundreds of watts to run.  The power supply connects to all of these devices and provides the needed power to each of them and they are happy and run at their expected level.

Fudge Room

First the power requirement each component requires is the max with some fudge room.  Depending on the quality of the unit then you can go over a little if you really want to go over the rating make sure to research the unit you are looking in to buying to make sure it even meets its labeled rating.

Not all Power Supplies are created equal and some are very much under performers and they can fail if they are put under too much load for too long.  Now the wattage rating of Power Supplies are not exact but most of the time they are close but some are not high quality and they perform below the expected rating.  So make sure to do your research when you want to purchase a Power Supply.

Also the older your components get the more power they may need.  This can impact a system getting up in years if the power supply was right at the limit of the components.  This can lead to the same issues as buying an under powered power supply from the start.

What Happens If Your Power Supply Is Too Weak

It depends on how much over your parts are to your Power Supply.  If they are only a little it will tax the power supply shortening its life sometimes dramatically.

An under powered power supply will result in random shutdowns and a lot more heat.  This will age your power supply dramatically and it will fail much sooner than it should.

When your power supply fails it fails spectacularly many people have reported their power supply failing and taking their motherboard, RAM, CPU, and any card hooked up to it (graphics cards, sound cards, WiFi cards…) with it.  Another great risk is fire if it gets too hot and dies then they sometimes can catch fire.

So buy an under powered power supply and you can fry your entire computer in the process and have to buy everything except the case again.

Constant Load Vs Peak

To make matters worse power supplies do not have a standard for rating.  Some rate their product with Constant Load and other only rate using Peak load.

Constant load is what you want to know the most this is how high it will function at all times and not suffer any.

Peak load is what it can achieve for a brief time as a max.  This is a meaningless number because it does not tell you what the constant load is and it does not tell you for how long the power supply can maintain this Peak load.

So make sure you research your power supply and see what its constant load is and make sure your components are under that number.  If the unit you are looking at does not have a constant load rating then steer clear and find a better one that does.

So Why Not Buy A Massive Watt Power Supply Then?

This is tempting and it is not as catastrophic as getting an under powered power supply, this isn’t advisable for most computer users.

The first problem is cost the higher the watts a power supply outputs the higher the price.  It will cost you more and you will never utilize it to its fullest.

The second problem is inefficiency if you draw less than 20% of any power supplies max rating it is far less efficient than if you are within the 40-60% portion of the maximum load.  This leads to a higher power bill then if you had invested in a power supply that fell in the 40-60% range.  You would have the most efficient use of your power supply and it will cost you less in the long run for your power bill.  Also this will leave some head room for future upgrades at the same time.

Power Supply Rating Scheme

Given that a power supply is a converter they are inefficient by nature.  It takes electricity to convert electricity, and there are losses involved as well.

80 Plus meaning; the 80 plus program was created to test Power Supplies and if they met 80% efficiency or above they were given an 80 plus rating.  This was the first rating but with the increasing efficiency they had to add more ratings so they added the Bronze, Silver, Gold, Platinum, and Titanium ratings to add to the 80 Plus.  Below is a table to better describe what the ratings mean, the short of it is Titanium is the highest rating we have right now.

Modular Power Supplies

Older power supplies had all their cables connected this meant that when you were done building your computer you had extra cables hanging around the inside of your case that you would need to tie up somewhere inside the case.  Enter the modular power supply where some or all the cables are able to be detached and stored outside of the case.

There are two flavors of modular power supplies semi-modular and fully modular.

Semi-modular have most cables able to be removed except the common needed cables which are hard wired in and unable to be removed.  This type of unit is mainly for keeping the inside of your case tidy and not having extra cables floating around the inside that are not connected.

Fully Modular are able to have all cables disconnected.  This can be handy when you need to remove the power supply but you do not want to have to disturb your cable management in the process you can just unplug everything and pull the power supply and not have to worry about messing with your hard work.

Now while these modular power supplies sound amazing and convenient they do have some drawbacks the main one being their cost.  They are more expensive than their standard non-modular counterparts so they will increase the cost of your build a little.  They sometimes can be bigger as well to accommodate the modular components.

Now with a premium price they normally come with premium features meaning their internal components tend to be higher end as well.


If you want the most bang for your buck and power efficiency go with a power supply that will run in the 40-60% band of your power requirements.  You pay more the higher the efficiency of the power supply unit.  If you do have an under powered power supply you risk a catastrophic failure that can take other components of your computer with it.

Cool master has a great calculator for your power supply needs here is a link.

If you have any questions comments or thoughts please feel free to leave them down in the comments section.

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