Power Supply Efficiency - 80 PLUS

[John P. Myers]

Alot of talk about power supplies lately with recommendations to get 80 Plus Silver or better. Some people may not understand what this means so i made a crappy table to help Note that these specs do not apply to server power supplies.

% of Load:	10%	20%	50%	100%
80 Plus	n/a	80%	80%	80%
80 Plus Bronze	n/a	82%	85%	82%
80 Plus Silver	n/a	85%	88%	85%
80 Plus Gold	n/a	87%	90%	87%
80 Plus Platinum	n/a	90%	92%	89%
80 Plus Titanium	90%	92%	94%	90%

This table shows the minimum efficiency required to get 80 Plus certification. For each test at 20%, 50% and 100% load, the power supply must meet the minimum requirements for ALL 3 (ALL 4 in the case of Titanium) in order to be certified.

Why does it matter?

Let's say you have a 300W power supply that's only 60% efficient, such as one you might find in a computer you got from Best Buy. If you run it at 100% load, you'll get your 300W, but you'll draw 500W to do it, shooting your electric bill sky high. You might ask what happened to the other 200W? It's all converted to heat, which will make your air conditioning run more often, shooting up your electric bill even more, not to mention making it much tougher to keep your computer cool.

So you get fed up with the garbage power supply and get a basic 80 Plus 300W one. Running it at 100% load, you get your 300W, but only draw 375W to do it, producing only 75W of heat. Your wallet, computer and air conditioning unit thank you.

Let's say you get frustrated with the 80 Plus and decide to go all out on an 80 Plus Platinum. Running it at 100% load, you get your 300W, but only draw 337W to do it, producing only 37W of heat. Your wallet, computer and air conditioning unit throw you a party.

In this example, going from a garbage power supply wasting 200W in heat, to an 80 Plus Platinum wasting only 37W, you save 163W/h. That equates to 117.36 kW/h off your electric bill each month, or about $14.08 off your bill at the national average of $0.12 per kW/h = $169/year.

The savings are even more on larger power supplies, as only a 300W was used in this example. The savings are greater still when you get a power supply that can provide more wattage than you need, meaning it runs at a 60% load which is more efficient than maxing it out (45%-70% load is best).