As the number of personal computers grew in the early 1980s the EPA stepped in with some initiatives to help reduce the need for additional expensive power plants.

Acid rain was the main motivator as coal was still the primary source of power in the late 1970s.

Originally in the 1980s the CRT VGA monitor standard was developed to manage idle and standby power. CRT monitors use over 100W of power with active and < 5W at standby.

The Energy Star BIOS seen in personal computers in the early 1990s displayed at boot up was mostly marketing. The CPU idle power was eventually reduced to 1W and enthusiast video cards were able to reduce idle power eventually to 15W.

Power plants are expensive and sometimes hard to place. So power companies work with the EPA to develop solutions and over the decades the work has saved the need for hundreds of power plants. Consumers also benefit with reduced energy costs. Healthcare costs are another benefit that is often overlooked.

The new EPA Energy Star 5.0 specifications for computers became effective on July 1, 2009. They require the use of 80 PLUS Bronze level or higher power supplies. Our GTX 260s feature low idle power consumption which is mandated by the specifications.

Before 80 PLUS certification was introduced, most PSUs had 50% to 70% efficiency ratings. Most PSUs now meet the minimum standards of the 80 PLUS program, and it has become the market standard. PC power supplies tend to be replaced only when they fail..


80 PLUS Test Type 115 V Internal Non-Redundant 230 V Internal Redundant
Fraction of Rated Load 10% 20% 50% 100% 10% 20% 50% 100%
80 PLUS 80% 80% 80% Not defined
80 PLUS Bronze 82% 85% 82% 81% 85% 81%
80 PLUS Silver 85% 88% 85% 85% 89% 85%
80 PLUS Gold 87% 90% 87% 88% 92% 88%
80 PLUS Platinum 90% 92% 89% 90% 94% 91%
80 PLUS Titanium 90% 92% 94% 90% 90% 94% 96% 91%

There are several divisions with the titanium being the highest standard that requires efficient operation over a wide range of loads. 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.

Our TX850V2 is certified 80 PLUS bronze,r CS450M is certified 80 PLUS gold, HX1000i is certified 80 PLUS platinum . Testing them with a power meter: passed. The low cost $20 Killawatt power tester can also consider power consumption over time. The unit is definitely very eye opening and it pays for itself by alerting the user to real power consumption..

Over time the PC PSU market has expanded. 80 PLUS had segmented the market further. It was not until 2014 that 80 PLUS titanium power supplies started becoming available for gaming machines. The Corsair AX1500i is excessive but it represents the top of the range.

Swapping out an old PSU for a modern 80 PLUS model will save $ over the entire service life of the unit.


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HIBERFIL.SYS is the same size as system memory. Each new version of Windows improved the mobile capability however notebook vendors and BIOS developers were slow to modernize. ACPI was published in 1996 but it took several years to become pervasive.

A Toshiba Windows 95 notebook supplied software to support the Advanced Power Management capability.


Modern microprocessors are now using a varying multiplier to change the clock speed significantly. The effect is to reduce energy consumption when idle. AMD calls it Cool & Quiet and Intel calls it Advanced Speed Step. We have 2 different AMD processors and they both support the Cool & Quiet power savings. The Atom in our netbook supports Advanced Speed Step which Intel calls their CPU power management.

The AMD Phenom II X4 965 Black Edition 3.4 GHz can reach 1W of power when idle which pays for the CPU vs. the older Athlon64 X2 4200+ in idle power savings. The CPU is powerful enough to manage with dual graphics cards but it’s loaded hard when games are played which adds to the total power load.


JEDEC revises the standards as engineers are able to improve the production of memory products. JEDEC DDR3 is 1.5V however as 30nm was coming online, it was revised (DDR3L) to support 1.35V operation which uses less power. DDR3L-1600 is compatible with standard DDR3 and it can operate at 1.5V or 1.35V. DDR3 clocks are also managed by the CPU which can further reduce power consumption.


NVIDIA GeForce 200 series and above now support a lower power state when not being used for games. For example, a single GTX 260 uses about 200W when loaded but this falls to 27W when games are not in use. The GPU can dynamically change the clock speed depending on the load. The result is a spectacular improvement in power consumption when not in use.

Our GTX 660 Ti has more capacity to control the power consumption and in its idle state it operates at 15W to provide desktop functionality. Unlike the older GTX 260s, the GTX 660 Ti can hold the idle power level which reduces overall power consumption significantly better.

The latest video cards from AMD now have core shut down to save power when there is no load. This will benefit Dual GPU users as well as CrossFire users. Our HD 5450 has the one of the lowest idle power ratings at approximately 5W which compares with the power used by integrated graphics.


All power supplies are more efficient with the higher input voltage. With 80 PLUS power supplies the gain is under 2% which materially limits the benefits versus the cost of installing 230V service. The EU uses 230V while the US uses 115V.

230V is used in servers only because they need the power. A typical rack can need upwards of 35,000 watts. Servers also use ATX power supplies. Many have 2 PSU bays for fault tolerance. Over time better model power supplies have reduced the need for dual power supplies but most servers continue to use them.

Our Corsair CS450M is typical with much better efficiency at 230V. All power supplies are now designed for 90-250V while older designs used a switch. The 80 PLUS gold means the CS450M has to be at least 87% efficient. Notice how the AX1500i differs from the CS450M — both reach maximum efficiency near a 50% load.


The problem: many left their machines on 24 hours a day. The first significant reduction in power came from the screen which would shut down saving vast amounts of electricity. Old CRT monitors need about 2-5 time the power of the typical LCD. Our old Dell P991 could reduce power down to 3 W when in standby compared to 125 W when active. Our AL1916 needs about 60 W when active and less then 2 W when in standby. Our newer PA238QR uses 32-33W operating and yet it is very bright.

Many machines use more than a single hard disk so power down idle disks reduces power consumption. Modern desktop hard disks only need about 10 W of operating power and notebook disks need only about 2.5 W of power. The new SSD drives need about same power as a notebook disk.

CPU power today is very low. Early efforts worked on varying the voltage supply which can be reduced when idle. The power can be raised when the load is higher.

A more recent CPU improvement is the addition of a varying multiplier. This allows the CPU to reduce power to very low levels. Our Athlon on our server can achieve 3.51 W of power and its still able to handle web requests easily. Our Atom CPU in our netbook is even more miserly. Our Athlon can lower the multiplier to 5 while our newer Phenom can go down to 4 which improves the situation for a 125 W processor considerably.

RAM has also been brought into the power savings with a varying clock signal. When the load is light the main memory can slow down which reduces power. DDR2 needs about 10 W for each DIMM while DDR3 needs about 5 W per DIMM. The upcoming DDR4 will reduce power consumption even more.

Until NVIDIA introduced the GTX 200 series, their display adapters had no power savings features. We have a GTX 260 and it needs 197 W of power when loaded, but this falls to 27 W when idle. This saves a spectacular amount of energy when a gaming grade video card is used for work. AMD also has power savings and their HD 7970 boasts an idle load of under 3 W.

Chassis fans use little power however using better quality ball bearing fans reduce the noise compared to cheap brushless fans (sleeve bearing). Less noise is less wasted energy.

In recent years the power supply in a PC has finally seen an effort to boost efficiency. Our TX850V2 is over 82% efficient and more recent models are now over 92% efficient. The retrofit power supply market now moving more towards 80 PLUS gold. Corsairs RM line spans 450W to 1000W with many rival models to keep prices reasonable. Many other brands are now expanding into the lower market segments. Some internet stores still offer obsolete models, which works against the EPA’s mandate.

Our current workstation is a relatively powerful gaming platform. The entire machine is adequately modern enough to have extensive power savings throughout. As we incrementally upgrade the machine the overall efficiency improves significantly.

We estimate a gamer can save $50++ a month by enabling all power savings features. That is equivalent to a new AAA release day game every month.


When we replaced the GTX 260 SLI with the GTX 660 Ti, we saved over 250W of power when playing games. The GTX 260s have some power management. The GTX 660 Ti is much more refined. In use we note the GTX 660 Ti uses around 75W which saves over 300W of power.

The Corsair TX850V2 is built to the same standards seen in commercial datacenters. It’s 80 PLUS bronze which is materially better than previous models. The latest 80 PLUS titanium models are 94% efficient compared to the 82% efficiency of the TX850V2 which amounts to 25W maximum which is 10% of the gains from the GTX 660 Ti.

Obviously the GTX 260 SLI pressured PSU efficiency and capacity. The GTX 570 SLI is even more power hungry. With the GTX 660 Ti, excellent performance and much more energy efficient.

Max power nosedived going back to a single graphics card making the TX850V2 operate more like 80 PLUS silver. At present all games are very playable so there is no need for SLI but the GTX 660 Ti is much more energy efficient even with SLI. This makes a PSU upgrade a real tough sell, especially where electric rates are low. Graphics cards have made material improvements.

Today, GFLOPS per watt all that matters. This suggests that 20nm cards may needs under 100W of power to play Crysis 3 on maximum graphics. When 14nm graphics cards become available then the power required will likely be under 50W for the game on maximum graphics.


The duty cycle for a clock is 100% while a gaming PC maybe much less. A refrigerator does not power up all the time, it tends to vary with the seasons and how often its opened. A high power microwave is harder powered up for more than 10 minutes at a time.

Our TX850V2 was selected mostly for its capacity and capabilities. On average a person may play anywhere from 4 hours to 60 hours playing games in a given week. The power used by our GTX 660 Ti varies as a game is played, its not a flat line.

For a PC running 24/7 the idle load can be considered as a 100% duty cycle which means the maximum savings. The power savings with gameplay is marginal cost, i.e. the cost of an hour of gameplay. Saving 300W is a material improvement in the marginal cost of an hour of gameplay.


Payback is directly proportional to electric cost and the duty cycle. Over in Germany, rates are 48 cents per kilowatt hour. Many have solar panels installed due to the high cost of electric power. We pay under 10 cents per kilowatt hour.

Assuming a rate of 11 cents per kWh, each 1W saved for a 24/7 device saves $1 in operating costs annually. With lower prices for 80 PLUS Gold power supplies, its increasingly advisable to consider retrofitting older power supplies immediately.

With over 300W of loaded power reductions and a 35W reduction in the idle load, the GTX 660 Ti was strongly indicated. The card saves $$ regardless of use. We bought the card primarily to perk up gameplay. Many games now want DX11 hardware but the GTX 660 Ti is an enthusiast grade video card which can play modern games, mostly with high graphics.

The real gains are with idle power levels. The CPU is down to 1W, the GTX 660 Ti is down to 15W.  The payback for us is 15 years, but over Germany its down to 18 months.

Moving to 80 PLUS titanium (94%) does save $ but payback is rather limited given the GTX 660 Ti. The EU with higher rates can find better advantage. The enthusiast TX850V2 is very tough act to follow.

80 PLUS gold power supplies are starting to move into the lower cost market segments displacing the 80 PLUS bronze models. Over time as new machines are assembled and replacement power supplies are installed, the EPA goals are now finally becoming pervasive. The Corsair CS450M is a low cost 80 PLUS gold model that has pressured the obsolete bronze market.

If you need a replacement PSU, read our page on them. While intended for gaming, the page has general information of use for all.


The new EPA Energy Star 5.0 specifications for computers became effective on July 1, 2009. In 2014, 80 PLUS power supplies are widely available. We expect that come 2019 to see the savings exceeding $100 million dollars just from personal computers.

Some savings are harder to measure, such as reduced lung disease from needing new power plants etc. Healthcare costs continue to rise making the EPA initiatives even more desirable.

Desktop PC sales have slowed somewhat as more people buy notebooks or tablets. The PSU for most notebooks is notorious for not being very efficient. At present nobody reviews the notebook power supply at all.