Is it worth purchasing a high-efficiency power supply?
If you’ve gone shopping for a power supply any time over the last few years, you’ve probably noticed the explosive proliferation of various 80 Plus ratings. As initially conceived, an 80 Plus certification was a way for PSU manufacturers to validate that their power supply units were at least 80% efficient at 25%, 50%, 75%, and 100% of full load.
The 80 Plus program has expanded significantly since the first specification was adopted. Valid levels now include Bronze, Silver, Gold, Platinum, and a currently unused Titanium specification level. The chart below lists the requirements a PSU must meet to be certified.
The 80 Plus PSU certification program
In the pre-80 Plus days, PSU prices normally clustered around a given wattage output. The advent of the various 80 Plus levels has created a second variable that can have a substantial impact on unit price. This leads us to three important questions: How much power can you save by moving to a higher-efficiency supply, what’s the premium of doing so, and how long does it take to make back your initial investment?
Power supply pricing and premiums
First, here’s an overview of 80 Plus PSU pricing at various wattages and generic products are not part of these results. When we priced units, we opted for the lowest-cost unit from the same manufacturer.
PSU prices
Basic 400W-600W units are quite cheap these days, even from top vendors like Antec, Corsair, OCZ, and Cheiftec. Prices start to climb by the 700W range; 1200W units are several hundred pounds.
The price premium for greater-than-80 Plus certification can be considerable. Below 800W, Bronze certification adds 4-20% to the list price of an 80 Plus unit. 80 Plus Gold PSUs are 35-61% more expensive within the same wattage category. Platinum-level power supplies are 90-100% more expensive; twice the price of a standard 80 Plus unit.
At the highest end of the market, this changes slightly. Power supplies in the 1kW and greater category don’t put much of a premium on high-efficiency units. An 80 Plus 1200W PSU is £150.00 Plus Gold is £165.00 Plus Platinum is still suggestively more expensive at £185.00.
You can’t save power that you aren’t using
Power supply competence is defined as the amount of power actually provided to the internal components, divided by the amount of power drawn at the wall. A 50% efficient PSU that’s tasked with providing 50W of power to a system will draw 100W from the grid. The extra 50W is lost as heat. A 90% efficient PSU would draw 56W in the same circumstances.
Even generic PSUs are far more than 50% efficient; in fact, 75-77% is fairly mutual. This means the amount of money you save from upgrading to a high-efficiency PSU is minimal if you don’t actually draw much power to start with. Electricity rates are charged by the kWh — if your system only uses 80W at idle, and idles 20 hours a day, you won’t see much advantage from an 80 Plus Platinum PSU as opposed to a regular 80 Plus.