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Micronaut

Member

Registered: 2019-07-04

Posts: 250  

Power usage of SSDs

For a long time now I've been reading / hearing that SSDs use LESS power than old fashioned spinning disks. But today I happened to actually read the label on my Crucial BX500 SSDs and it says they can draw 1.7 amps!? The spinning drives I have are rated .48 to .55 amps. Is this a 'peak' vs 'average' usage thing? The SSD doesn't draw power when not being accessed but the drive with a motor has to be spinning all the time? Though I'm still puzzled that the SSD would have so much higher peak power draw...

RedGreen925

Member

Registered: 2024-12-07

Posts: 204  

Re: Power usage of SSDs

SSDs and it says they can draw 1.7 amps!? The spinning drives I have are rated .48 to .55 amps.

What is the voltage they are using with that amperage? If the SSD is using 5v and the HDD is using 12v then the power consumed is well over four times as much at the same amperage. When you double the voltage you quadruple the power drawn, it is a squared function. Actually my quick calculation is 5.76 times as much for equal amps drawn from 12v vs 5v as it is 2.4 times the voltage. A SSD is always drawing power too you will see the idle rating there somewhere too. You would need to determine the amount of each power voltage the drives use and the amps at those voltages to figure it out the total watts. The old amps x volts =  watts consumed formula comes into play to determine that.

zeus@9600k:~$ calc 2.4^2
5.76

Micronaut

Member

Registered: 2019-07-04

Posts: 250  

Re: Power usage of SSDs

The SSD just gives a 5v rating, and that's 1.7 amps. It's a 1 TB model. All of the Western Digital spinning disks I own say 0.68 amps at 5 volts and 0.55 at 12 volts. These are either 1 TB or 2 TB models. So that power calculation doesn't seem to work out for these. Maybe it's something peculiar to this brand? I'll have to see if I can look at the labels of other SSDs somewhere. Maybe I can get a closeup on a website or see one in a store...

RedGreen925

Member

Registered: 2024-12-07

Posts: 204  

Re: Power usage of SSDs

o that power calculation doesn't seem to work out for these.

SSD 5v * 1.7a = 8.5w

HDD 5v * .68a = 3.4w, 12v * .55a = 6.6w,  for a total of 3.4w + 6.6w = 11w, it uses both them voltages at the same time internally.

Seems to me the HDD uses more power, then again I know how to do the math.

Micronaut

Member

Registered: 2019-07-04

Posts: 250  

Re: Power usage of SSDs

If it's drawing from BOTH 12v and 5v at the same time, yes, it would clearly use more power. It's not clear from the label that it does so. Those ratings could be for different modes or different power connections. It's been a while since I had to worry about HD power.

But now I have a new thing to check on SSDs. Another brand I got access to, PNY, shows only 1 amp for a 2TB SSD. Quite a difference from the Crucial, and for more storage. Hmm....

Last edited by Micronaut (Yesterday 18:17:17)

rolfie

Member

Registered: 2017-11-25

Posts: 1,361  

Re: Power usage of SSDs

The power draw from any SSD is very much depending on the write/read load. The figures given are for full load at full speed plus a bit overhead. The average consumption will be very much lower.

But to be considered: PCIe3 consumes less than PCIe4, less than PCIe5.

Micronaut

Member

Registered: 2019-07-04

Posts: 250  

Re: Power usage of SSDs

That's interesting. Now you're talking about the 'card' drives that don't even use SATA connectors. Power usage doesn't seem to be linear there, either.

Out of curiosity, I popped the cover on a laptop I have to see the tiny little HD. It's only got a 5v rating, and it's .55 amps. The motor must be running in the 5v feed along with the electronics. So now I'm really questioning whether SSDs are automatically less power hungry than spinning disks.

At least these disks I have already bought are intended for desktops. I just want the faster load times. But if I decide to get SSDs for my laptops, I will be shopping very carefully...

Last edited by Micronaut (Yesterday 19:07:53)

tux_99

Member

Registered: 2025-06-17

Posts: 55  

Re: Power usage of SSDs

The main selling point of SSDs has always been access times, not power consumption, although SSDs do generally consume less power than hard disks when idle.

stargate-sg1-cheyenne-mtn

Member

Registered: 2023-11-27

Posts: 432  

Re: Power usage of SSDs

used ssd for years and they definitely extend battery life on laptops

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rolfie

Member

Registered: 2017-11-25

Posts: 1,361  

Re: Power usage of SSDs

Now you're talking about the 'card' drives that don't even use SATA connectors. Power usage doesn't seem to be linear there, either.

Generally spoken, there is not much difference between SATA SSDs in the typical 2,5" housing and these typical 2280 M2 cards as used for NVME drives. The power consumption on all of them are load frequency dependent.

And as a matter of fact, SSDs are in average of much lower power consumption as the spinning rust drives. Don't look at the rating, this is a max consumption value a drive rarely takes in in very extreme situations (and gets very hot and slows down to protect).

steve_v

Member

Registered: 2018-01-11

Posts: 548  

Re: Power usage of SSDs

All power ratings on drives are peak values (for sizing power supplies etc.) unless otherwise specified. They have very little bearing on average power consumption, which will vary wildly with workload.
It's not as simple as "smaller number less power" either, since a faster drive will usually draw higher peak power, but get its work done quicker and drop back to idle sooner.

The only accurate  way to compare is, as always, to stop obsessing over manufacturer specifications and actually measure power consumption under your specific workload.

SSDs generally draw peak power under sustained write workloads, HDDs at spinup / spindle start.
The big power saving from SSDs comes from write-heavy workloads being intermittent, idle power draw being very low, and the transition being practically free.

With a HDD you have to choose between keeping the spindle running all the time (thus higher idle draw), or starting it only when needed (incurring access delays and spikes to near peak current).
For laptops there's the added complication of a spinning drive (i.e. unparked heads) being vulnerable to physical shock, so they usually run very short spindown timeouts - that's great for power consumption if the drive is usually idle, but terrible if it has to spin back up every other minute.

There's also an advantage in SSDs not needing to physically move heads around, so all areas cost the same to access (caching complications aside) and reads can use much less power than writes (typical workloads often being more read than write).
The power consumption of a HDD for a given operation will vary with where it is on disk, i.e. how many seeks and how far, and seeking to a read location uses just as much power as seeking to a write. (upshot: defragging your rust not only makes it faster, it also saves energy )

PCIe3 consumes less than PCIe4, less than PCIe5.

Again that's peak power, and it's simply because faster drives use more power under load. The bus itself makes very little difference in the real world, because ASPM.

Last edited by steve_v (Today 02:30:40)

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