X51 330W PSU Output

Just a very quick follow up question, if the power brick has an 80% efficiency, and my current reading of 200W is from the bricks input, would the amount the computer itself is actually consuming be 160W (80% of 200)?

Truthfully I don't really know if it does. I kind of doubt the PSU is a 80+. My guess is since it's a power brick and not a standard PSU it's not but that is just a guess. I do know Dell uses 80+ PSU's because the PSU in my Area 51 is a 80+.

I do know a 80+ certified PSU means it is efficient at 20,50 and 100%. It will give you clean power and not spike or be way off from what the volts are meant to be. It will also pull less off the wall then a non certified PSU will. What I've read a lot on forums and such is you want to stay at 80% or so. More and it strains the PSU to much and can cause it to fail much more quickly. You also do not want the other extreme and go to low of a draw.


Here is what Wiki has to say about 80 Plus. It can explain it better then I can.  http://en.wikipedia.org/wiki/80_Plus 

80 Plus

80 Plus (trademarked 80 PLUS) is a voluntary certification program intended to promote efficient energy use in computer power supply units (PSUs). Launched in 2004 by Ecos Consulting, it certifies products that have more than 80% energy efficiency at 20%, 50% and 100% of rated load, and a power factor of 0.9 or greater at 100% load. That is, such PSUs will waste 20% or less electric energy as heat at the specified load levels, thus reducing electricity use and bills compared to less efficient PSUs. Sometimes, rebates are given for manufacturers who use 80 Plus-certified PSUs.

Technical overview

The efficiency of a computer power supply is its output power divided by its input power. The remaining power is converted into heat. For instance, a 600-watt power supply with 60% efficiency running at full load would draw 1000 W from the mains and would therefore waste 400 W as heat. On the other hand a 600-watt power supply with 80% efficiency running at full load would draw 750 W from the mains and would therefore waste only 150 W as heat.

For a given power supply, efficiency varies depending on how much power is being delivered. Supplies are typically most efficient at between half and three quarters load, much less efficient at low load, and somewhat less efficient at maximum load. Older ATX power supplies were typically 60% to 75% efficient. To qualify for 80 Plus, a power supply must achieve at least 80% efficiency at three specified loads (20%, 50% and 100% of maximum rated power). However, 80 Plus supplies may still be less than 80% efficient at lower loads. For instance, an 80 Plus, 520 watt supply could still be 70% or less efficient at 60 watts (a typical idle power for a desktop computer). Thus it is still important to select a supply with capacity appropriate to the device being powered.

It is easier to achieve the higher efficiency levels for higher wattage supplies, so gold and platinum supplies may be less available in consumer level supplies of reasonable capacity for typical desktop machines.

Typical computer power supplies may have power factors as low as 0.5 to 0.6. The higher power factor reduces the peak current draw, reducing load on the circuit or on an uninterruptible power supply.

Reducing the heat output of the computer helps reduce noise, since fans do not have to spin as fast to cool the computer. Reduced heat and resulting lower cooling demands may increase computer reliability.

The testing conditions may give an unrealistic expectation of efficiency for heavily loaded, high power (rated much larger than 300 W) supplies. A heavily loaded power supply and the computer it is powering generate significant amounts of heat, which may raise the power supply temperature, which is likely to decrease its efficiency. Since power supplies are certified at room temperature, this effect is not taken into account.

80 Plus does not set efficiency targets for very low load. For instance, generation of standby power may still be relatively inefficient, and may not meet requirements of the One Watt Initiative. Testing of 80 Plus power supplies shows that they vary considerably in standby efficiency. Some consume half a watt[10] or less in standby with no load, where others consume several times as much at standby, even though they may meet higher 80 Plus certification requirement levels. Inefficiencies in generating standby power are magnified by the amount of time that computers spend turned off.