Power usage laptop vs. desktop

What uses less power when plugged into AC, a desktop or a laptop?

I think it's the laptop but I'm not sure. How much would the difference be. Let's say they're about equally configured: Intel chipset, IGP, one harddrive, Intel C2D 2.0Ghz.

I'm asking because often my laptop is on all day and was wondering what would happen to my powerbills if I upgrade to a desktop.

PS. I always remove my battery.

 

there are too many variable to account for in this calculation. mobo? chipset? graphics card? efficient power supply?

What are you worried about? Power usage or cooling? I have a server that is on 24/7 to stream to the various media extenders and HTPCs in my home. C2D 2.66ghz, Asus P5Q mobo, a Geforce 7300 graphic card, 12 HDDs = around 200w idling.

 

let's say a santa rosa Intel 2.0GHz laptop.
and some middle of the road Intel C2D desktop.

Both Intel IGP. Both one harddrive, one DVD drive.

Power usage / Power bill. leaving it on 24 hours a day, how much it would cost me.

 

Naturally laptop. Without any hard numbers, laptops are designed to be more power efficient in general, and to be cooler. Even with the same components, everything in a laptop is designed to use less power, they don't use the exact same component, they is usually a desktop and laptop version.

 

Obviously the laptop. Think about it: the AC adapters on "powerful" laptops are rated for 90 watts, while even the most basic entry level desktop has a 250 watt PSU.

 

Yes I think you are right. Thanks. I would still be interested in some numbers about the real power draw though.

I know my laptop draws about 15-20 watt when on battery. Is it the same on AC?

I thought about that, but then I thought my laptop does not actually use 90 watt. Maybe a really power efficient desktop could use way less than 250 watt.

 

Depends on your power management settings in the BIOS and the OS. Do you run the screen brighter when plugged in? Do you have different settings for processor speed management when on battery? Do you run some hardware in standby/low-power mode when on battery?

Are we counting the monitor or not? If so, what type and size monitor is it?

 

The laptop is on battery and on AC both in the highest performance settings (same).

Oh yeah, forgot to say: screen is turned off because I use an external monitor.

So both desktop and laptop would be using the same screen.

 

Some hard numbers: I've got my Dell E6400 (Intel graphics) plugged into a mains power meter and, as I type this, it is drawing between 15W and 21W. If I run a benchmark program such as 3DMark06 then the power consumption rises to around 45W.

A couple of years back I assembled a desktop computer with AMD 3200+ CPU and ATI integrated graphics which only needed 60W on idle (including 17" LCD monitor), so maybe 40W without the monitor. Cool 'n' quiet was a design objective and I succeeded.

Basically, standard desktop components will draw 2 to 3 times more power than their notebook equivalents. If, from my numbers above, that difference is 40W, then the extra power is about 1 kilowatt hour per day.

However, that extra power consumption can have side-effects: The desktop computer can provide an extra heating in winter and offset the general heating bill, but in summer the excess heat can increase the air conditioning bill.

John

 

Great answer, exactly what I was looking for.

 

My laptop uses 49W @ idle and 68W @ full load. See specs in signature. This is without the external monitor.

My desktop i had before this one that had pretty much the same "power" did take about 150W idle and 180W full load including the external monitor in sign.

I have a power meter too.

 

It only gets worse when u compare a notebook to a gaming desktop. I believe the 9800 GX2 draws somewhere in the region of 250 Watts or more (well somewhere in between 200 and 300+).

That's like four top end gaming laptops there.

 

Phil, their are power supplies which you should look into.

The cheapo desktop power supplies do not have active PFC or the ability to control amperage output from the main transformer.
SO a cheap 250 watt power supply will actually use more power than say a 600 watt one like the green power series from Seasonic.

I think Seasonic and Pc Power are the only brands which offer power supplies which can control amperage and keep the power intake as low as possible.

Plus most desktop power supplies are 85% efficient, whereas a laptop one may be around 60% efficient.

A desktop will in the end use more power, and it will not be a cost effective solution.
Reason being, that desktop with a good amperage regulated power supply, costs like $120 and the system will probably $500 or more, and that will cost much more than what you are paying on your monthly electric bill.

K-TRON

 

I think that the majority of notebook PSUs have better than 60% efficiency. Possibly around 75%. My example quoted above is using a Dell Latitude D series PSU and if that's only 60% efficient then it means the computer is only using 11W without any power saving measures being enabled. That is unlikely since when running on battery various power saving measures have to be used to get the power drain down to 11W or below.

I would always expect the desktop to use more power. The CPU isn't selected for low power consumption, the chipset is unlikely to have so many power saving measures in place and the HDD and ODD are bigger and tend to use more power.

John

 

wow, two days without sleeping caused that mistake.
I meant more

I tried to state that it would not be cost effective and it will use more power.

K-TRON

 

Thanks guys. I'll keep using my laptop as a desktop for now.

 

No problem. Get more sleep.

John

 

Will using a laptop hooked up with a 15 o 17 inc LCD monitor result in less wattage use against using a full desktop setup? I'm trying to reduce my house bill

 

I'm almost certain that this has been brought up, but most AC adatpers for laptops are only 65w/90w max. A lot of desktops are 100-200w+. Do the math.

 

My Quad core Q6600 desktop system came with a 350w psu , I soon replaced it with a 600w version.

Regards

John.

 

The PSU rating indicate a maximum power consumption. The actual consumption is likely to be less.

A better indicator is to put your hand near the fan exhaust and compare the amount of hot air coming off each under different usage conditions.

John

 

For $18 you can stop guessing by using one of these power meters.

I've been using them around my house for years. A general number for desktop systems is around 60-100W at idle, and 200+W at full load. External LCD monitors run around 30-60W. Most Centrino-and-newer era notebooks run around 30-ish W at idle, and maybe 40-50W at load, including the monitor.

 

Ralf, most of teh calculators are very inaccurate.
The only real way to know exactly how much power a desktop uses, is by having one of those devices which plugs into the wall, which you plug the system into.
It will be able to read the load an wattage used by creating an instantaneous short on the line, thus reading the amperage used, and thus the wattage used can be determined.

K-TRON