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Efficient Power Supply Contest
A reader writes: "In the June (paper) issue of Scientific American, there is a mini-article descibing the energy being wasted by power supplies in computers. Those things are only 60-70% efficient in converting line-voltage AC to low-voltage DC, and there are so many millions of them out there that a modest efficiency increase could trim $1billion or more from the annual energy costs of the USA. Well, various governmental agencies are seeking to get improved power-supply efficiency into the marketplace. The central "clearinghouse" site is at efficientpowersupplies.org, and details of their contest are in this PDF."
I'll give 2:1 odds its down before 10 comments are posted...
Please enjoy Google's version of the main page (efficientpowersupplies.org)
Please enjoy Google's HTML Version of the PDF.
I promise no Karma Whoring, courtesy of your (sometimes) friendly AC :)
You can also check out power supply reviews on Silent PC Review. They concern themselves with efficiency since an efficient power supply can be quieter and produce less heat.
The site also has a lot of other good info.
Switching supplies can approach 90% efficiency if they are carefully built. Such supplies will cost more, naturally, but an improvement from 60% to 90% efficiency will save you the extra cost over the course of a year or so. And, of course, you can feel better that you are contributing slightly less to carbon dioxide emissions.
The Opportunity Power supplies are one of the crucial building blocks of a modern society, converting high-voltage alternating current (AC) into low-voltage direct current (DC) for use by the electronic circuits in office equipment, telecommunications, and consumer electronics. Over 2.5 billion AC/DC power supplies are currently in use in the United States alone. About 6 to 10 billion are in use worldwide.
While the best power supplies are more than 90% efficient, some are only 20 to 40% efficient, wasting the majority of the electricity that passes through them. As a result, today's power supplies consume at least 2% of all U.S. electricity production. More efficient power supply designs could cut that usage in half, saving nearly $3 billion and about 24 million tons of carbon dioxide emissions per year.
The Purpose of This Web Site This Web site was created by EPRI PEAC Corporation and Ecos Consulting to initiate a global dialogue about energy efficient power supplies. Our focus here is particularly on the issue of energy consumption in the active or "on" mode of product operation. According to our research so far, nearly 75% of all the energy used by power supplies occurs in active mode. For those interested primarily in standby power consumption or other low-power modes, please visit Lawrence Berkeley National Laboratory's Web site on that topic at http://standby.lbl.gov.
The California Energy Commission's PIER (Public Interest Energy Research) program has funded Ecos, EPRI PEAC, and the Energy Innovation Institute (E2I) to assess the efficiencies of modern power supplies and recommend strategies for improving them. An open exchange of design information, test methods, measured results, and other related documents is essential to that project's success, tapping the best information available from manufacturers, government agencies, utilities, and product users.
In addition, Ecos and EPRI PEAC are working on a variety of other power supply efficiency initiatives in the U.S., Europe, and Asia, described in more detail under Projects. Our goal in every case is to accelerate the market for more energy-efficient products, saving energy and preventing pollution.
How You Can Get Involved
Chaos will always win out over order because chaos is more organized
The power supply in my S-100 bus Z-80 computer weighed about 20 kg. Apple was one of the first microcomputer companies to use switching power supplies.
Mea navis aericumbens anguillis abundat
I was under the impression that a 400W power supply was capable of outputing 400W of power, not that it took as input 400W of power.
Casual Games/Downloads
by switching from energy guzzling CRTs to cool power efficient flat screens. I went from a 19" CRT at 350w to a 19" flat screen at 50w quite painlessly.
I doubt you could achieve that kind of savings no matter how power efficient you made the PS.
NPR ran a story about an initiative of larger companies simply turning off monitors when not in use. It goes into detail about green PCs and why it hasn't been a larger impact. It goes on to saying that a small group of people is ultimately making the decisions costing billions but in today's economy companies are doing more and more to survive - I'll stop and let you can read and make an interpretation.
[wallwarts with the load unplugged] are still converting even though it's more efficient than normal since there is smaller load.
Actually, they're LESS efficient than normal. With no load, ALL the power they consume is wasted - efficience is 0%. B-)
Now the total AMOUNT of waste IS typically lower. But it's not trivial. Even the lowest tech wallwart burns power heating copper in the transformer and making up leakage in the capacitors. If it has a switching regulator it's also burning a bunch of power keeping that alive. And a voltage-flattening/capacitor-discharging resistor actually INCREASES the amount of power wasted in the wart when the load is gone (by eating some of the power that WOULD have gone into the load).
So why waste ANY by leaving the wart plugged in?
You can guesstimate the power by feeling the wart when it's been sitting there with no load for a while. The hotter, the more waste.
Bantam Dominique roosters crow a four-note song. Once you've heard it as "Happy BIRTHday" you can't NOT hear it that way
DC power supplies are usually distributed because resistive (heat) losses in wires are proportional to current^2. Since power supplies consume a relatively contstant amount of power=voltage*current, a higher voltage will result in a lower current, which means less power given off as heat; if DC was produced in the basement, thick (and expensive) copper wires/busses would be needed to distribute it. In fact, the reason AC was chosen over DC for the power grid was because AC could be stepped up to higher voltages and therefore produced at a far away central location.
--- You shall know the truth, and the truth shall make you mad- Neal (not Cowboy) Boortz
Switching supplies can approach 90% efficiency if they are carefully built.
A downside of high efficiency is that the energy lost to heating is a tiny fraction of the energy handled. When certain components start to fail they can increase their losses - and this increases the heating. The higher the overall efficiency, the greater the extra heating is as a percentage of the NORMAL heating.
If this is not taken into account in the design of the supply (and its cooling budget), the supply may be prone to thermal runaway and catastrophic failures as components age.
Bantam Dominique roosters crow a four-note song. Once you've heard it as "Happy BIRTHday" you can't NOT hear it that way
That maybe the case, but it doesn't change the basic logic. If a 500W is 70% effecient, then it is pulling in 715W. If 500W is what you need, then at 90%, you now only need a PS that pulls 555W. Dropping almost 200W from your input, decreases your heat, decreases your fan requirement, decreases your output (and therefore input) requirement. See?
OK lets say your PC is drawing on average 300 watts not to hard to do with a modern machine. At 15 cents a kwh over a month thats slightly more than 32 bucks, my laptop maxes out at 60 watts and thats charging the battery it's normaly about 30 or a thenth of that figure but even at may I would be saving 26 bucks a month. I live in the north east so the cost is a lot higher than average here the best I could find was 2001 data that put it at 8 cents national residential average.
No sir I dont like it.
Except that LCDs use less Watts than a CRT.
Just a Tuna in the Sea of Life
1) Because the whole electronics industry has already been built up on electronics based on DC supplies, all chips, the circuits learned in EE class for common functions, etc.
2) The semiconductor technology that 98% of our electronics know-how is based on operates on low voltages, so you'd have to convert the higher 120-220-400 line and transmission voltages to low voltages anyways.
3) Most electronic active components in our current technology (semiconductors, even tubes), are asymmetric with regards to polarity and do not have "friendly" characteristics with truly bipolar (AC) signals and supplies.
4) Much of electronics can be viewed as tasks in signal processing, particularly signals that vary in time. AC power is itself electrical power that varies in time (e.g. 50-60hz). Therefore using AC as a supply into circuit would inherent introduce a LARGE signal on top of any signals you were actually interested in.
5) Batteries are inherently DC sources, so making circuits that can run of both batteries and an AC power source would be more complicated if the circuit required AC to run (you'd have to build the equivalent of a DC->AC inverter which is considerably more difficult than a AC->DC power supply, and doing so would waste battery power (inefficiencies in conversion), which is much more precious in most applications than wasting power originating from an AC powerline source.
Some large buildings have very large flouresent ballasts in the basement (or where-ever) because they can more effectively provide that power as a large unit rather than hundreds of small units.
What if the same idea where applied to computers. Right next to the standard wall outlet would be a world standardized jack with six or eight pins for each of the required voltages.
Computer supply voltages are VERY LOW - and trending lower. That means, for a given amount of power, their currents are VERY HIGH. Losses in wiring (for a given size of wire) go up with the SQUARE of the current.
The result is that you'd need to wire such outlets with fat copper bars, rather than "wire", to avoid losing far more in the wiring than you'd gain in the improved power supply in the basement.
Computer requirements (especially voltages) are rapidly changing, the voltages have to be well regulated (meaning you need regulation after the outlet anyhow), and a lose connection interrupting one of the set of voltages can be big trouble. So you're stuck with power supplies in the box.
(Indeed, makers of some high-reliability networking devices, including the company where I work, put a set of power supplies on EACH CARD, rather than depending on a redundant pair in the box to power all the cards.)
Bantam Dominique roosters crow a four-note song. Once you've heard it as "Happy BIRTHday" you can't NOT hear it that way
whoa, wait a minute. Most UPS's connect you directly to the AC lines. They only switch on to the DC-to-AC circuit when power is lost.
No inefficiency there buddy. Most of the time you're just connected to the AC lines like normal.
AC, or Alternating Current, is like a sine wave. The voltage swings from a positive peak to a negative trough, and the current switches direction when the voltage changes polarity. If you apply current to the gate of a transistor the wrong way, it stops working and will probably break. Therefore, everything that uses transistors uses DC, or Direct Current, where the electricity flows one way, and at a consistent voltage.</SIMPLIFICATION>
That's because frequently those electronic doodads are computers, just not computers with a hard drive and a monitor. They have CPUs and RAM inside. Even if said electronic thingamajig is not a computer, it probably has transistors in it, hence the DC power.We use AC power instead of DC power because we use a centralized power grid.If the world moves to distributed power generation, we'll likely abandon AC entirely. Of course, we'll never be completely free of power bricks, because our devices need different voltages. However, DC to DC conversion is much simpler than AC to DC conversion.
It's called a "marine battery." You ditch the internal power supply and feed DC from an external battery (through a voltage regulator) directly to the motherboard. I essence you've now turned your desktop into a descrete componant laptop (for sufficiently large values of "lap"). It's really not that hard.
Now, since you're never running on anything but battery power, you don't need most of the functionality of the common UPS. Your computer's own power managment takes care of all that.
And the beauty of it is exactly where you say it is, you can now draw your energy from any source that can produce electricity. That could be a battery charger plugged into your wall socket, or it could be a solar panel sitting on your cabin top, a small wind turbine sitting on your taffrail, a water turbine being dragged behind, a hand cranked/pedal powered generator, or even, yes, hamsters.
It's completely source agnostic upstream from the battery.
Your case is also smaller and cooler, but your "UPS" is no bigger or heavier if you already use an "enterprise class" (warp overclocking Mr. Sulu!) UPS.
Frankly, so far as I can tell, the only reason we do it the way we typically do it (if you're not a boater or RVer) is because we've always done it that way. We've declined to reinvent the wheel when such might actually be appropriate, chosing instead to add wheels to the existing wheels in extending chains of Rube Goldbergesque functionality.
KFG
You would STILL need heavy busbars with 12VAC, for the same reason you would need them with low voltage DC--VOLTAGE DROP.
Also: Heating. It's the CURRENT that heats the wire. The limit on wire size in a wall is keeping the heat down enough that it doesn't set the walls on fire.
Your house is wired with #14 for 15A circuits, #12 for 20A, #10 for 30A.
At 120 volts a puny 15 amp circuit can provide 1650 watts, enough to run a space heater with leftovers for a couple 75 watt bulbs, or all the lights in several rooms. 20A will feed several motorized appliances or your whole computer room. A dual 30A feed easily handles an electric stove and oven, or an electric drier.
At 12 volts a 20A feed would be maxed out by four 60 watt desk lamps or a couple 100 watt ceiling lamps. (Forget the toaster.)
Yes, you'd need bussbar. Every 12V circuit would require TEN TIMES the amount of copper as a 120V circuit to provide the same amount of energy with the same percentage of it heating the walls.
That goes for the line cords, too.
Bantam Dominique roosters crow a four-note song. Once you've heard it as "Happy BIRTHday" you can't NOT hear it that way
That's pretty much what modern switching power supplies do! If you were to examine the circuitry in (for example) the typical PC power supply starting from the AC input you will find a safety fuse, line filtering, a bridge rectifier, and a large storage capacitor. At this point the AC input has been rectified into high voltage DC.
What follows is a large power transistor (the switching element) and a "flyback" transformer. The transistor is switched on and off at a high frequency (something like 56kHz) and this energizes the primary side of the transformer.
The secondary side of the transformer has multiple taps, each tap responsible for one of the common voltages used in a PC (3.3, 5, 12, -5, and -12.) The taps output pulses so there is an additional rectifier and filter network (usually consisting of an inductor and capacitor) on each output from the transformer. One of the outputs (usually the one with the highest expected load) is monitored by the switching regulator control circuit. The controller adjusts the duty cycle (pulse width) of the switching transistor to regulate that monitored output voltage.
The other voltages (the non-monitored voltages) often have "post regulators" which can be linear or switching types. So, for example, the "-12" from the flyback might actually be -14 and there is a linear post-regulator to keep it at -12. In really crappy (common) PC power supplies they just leave out the post regulators and specify that the monitored output has a tight tolerance (example, 5V +/- 5%) where the non-monitored outputs have wide tolerance (12V +/- 10%) In such a power supply, the 12 volt (non-monitored) output will vary widely based on the load present on the 5V (monitored) output.
The efficiency of such a power supply varies widely based on details of the design. It is possible to design a highly efficient switching power supply (example, 90% efficient) but such power supplies are generally a lot more expensive. Some techniques to increase efficiency include:
* Instead of the multiple-tap flyback transformer, use a separate transformer for every output voltage or at least for every output voltage that has a significant load. So, you might use completely separate regulators for the 3.3, 5, and 12 volt outputs. The load on the -5 and -12 is usually quite small so these don't warrant fully independent regulators - linear post regulators are fine. The disadvantage of using truly separate regulator circuits is that N times the amount of circuitry is required which drives up cost and physical space requirements. Better PC power supplies actually have 3 regulators: one for the +5 standby (relatively low current, always active), one for the combined +5 and +3.3, and one for the +12.
* Increasing the switching frequency of the regulator can also increase efficiency. One problem is that better quality components are required - in particular the transformer and switching transistor. Also, the circuit layout is much more critical as the switching frequency is increased. Circuit layout can be a challenge when a design must fit an existing form factor (such as the shape of a typical ATX power supply.)
* Power factor correction (there is both active and passive types.) Power factor correction attempts to shape the utilization of energy to match the AC waveform. You can imagine the problem: without power factor correction, a switching regulator consumes energy in high frequency pulses that do not have any relationship to the AC waveform. Passive power factor correction essentially adds a filter network to the AC input. In active power factor correction the switching controller "knows about" the AC waveform and can adjust pulse width best utilize this. Some of the better PC power supplies (the more expensive ones) have active PFC.
No, your question and your understanding was valid. The power rating on a power supply states what maximum power the supply can deliver to its load. The actual power consumed *from* the power supply is solely a function of the load attached to it (i.e. the "computer" components it runs). The actual power consumed *from* the wall outlet is the sum of the power consumed by the power supply's load (i.e. the computer components) plus the extra power consumed by the power supply (i.e. the waste) which is directly proportional to the power supply's efficiency.
WarriorPoet42 got it right the second time around - but this did not make your question "stupid."
BY THE WAY: Just because you have a 400W power supply in your PC does NOT mean you are consuming 400W of power from the AC outlet. If you put an older (slower) CPU/mobo with no expansion cards, and run, say, a modern low-power hard drive, etc., the LOAD presented to the 400W power supply will be much lower. Think about it. Small form factor PCs are often built with 150W power supplies. This means that the components NEVER consume more than 150W, and probably seldom if ever hit that peak.
A side-effect of this is that the power supply efficiency does not necessarily always *waste* its ratedpower-minus-(1-minus-efficiency).
(whaatt??) Let's say:
R is the power supply's rated power.
E is its efficiency expressed as a fraction of 1 (i.e. 90% efficiency is expressed as 0.9)
So, a 400W (R=400) power supply with 80% (E=0.8) efficiency will *waste* 400*(1.0 - 0.8) 80 watts of power. But ONLY if the LOAD is drawing the full 400 watts of power!
Now let's say we have a 400W power supply with 80% efficiency, but the computer components only draw 180W of power. Let's use C to represent the power draw of the computer, so C=180. Now, just substitute C for R and you get:
C*(1-E) = 180*(1.0 - 0.8) = 36W. This is what you are REALLY losing due to power supply inefficiency.
Note: A switching power supply will have some minimal losses even if there is NO load attached to it. These are small compared to the efficiency losses in normal operation, so for practical purposes may be ignored. You could add a constant (say, K) to the equations above to account for this static power loss in the power supply, but K would be small, when compared to C, so has little effect on the math....
You'd think so but:
When a wall-wart, or most any power supply is plugged into the wall, the first thing the power connects is a transformer, and then goes directly to the wall. It is 100% all the time connected to this transformer, and conducting current through it, even though the device on the other side of the transformer isn't picking up any juice. A transformer is just two coils spun together around a common axis. Both coils have inductance and resistance, and the "main" one is always powered as long as the device is plugged in.
Now, switching supplies are a different story. They use a transistor (to simplify) in line with the main coil to "chop" the AC voltage up into an even quicker AC. Higher frequency voltage transmits much more efficiently through a transformer, so you can have a much smaller/cooler transformer for the same power output level. They also have the added benefit of being able to completely shut off the main coil when the secondary doesn't need any (with some supporting circuitry which always has a very small power draw, but it's much better than the always-on draw of a big coil).
-Jesse
Nothing says "unprofessional job" like wrinkles in your duct tape.
Seasonic Super series power supplies. My UPS load meter registered a ~15% drop in PC power consumption after I switched to these from Antec. Highly, highly recommended.
/sys/devices/systsem/cpu/cpu0/cpufreq/scaling_sets peed to match the power/performence balance you think is best. See the Athlon 64 Processor Power and Thermal Data Sheet. For example, a current top-of-the-line Athlon 64 3800+ burns 89W at 1.5V at maximum (better than Intel, but still a lot). If you lower the clock speed by 200MHz, the chip burns 72W @ 1.4V, another 200MHz lower burns 53W @ 1.3V, and another 200MHz lower burns 39W @ 1.2V. You can cut it all the way back to 22W max, 1000MHz @ 1.1V. With the current Fedora Core 2 kernel and a power management daemon like powernowd the speed will be adjusted automagically, but if you want to run Folding @ Home without excessively spiking your electric bill it's nice to set a fixed speed manually.
Also, use AMD 64-bit CPUs and set
The Mobile Athlon 64 3200+ (62W @ 1.4V max) is interesting if you really want to limit power consumption. I put one in my ASUS K8V Deluxe motherboard (Zalman CNPS7000A-AlCu heatsink, be VERY careful not to overtighten it and crack the unprotected core as there's no protective aluminum lid like on the desktop CPUs, not all heatsinks will fit). Drop 200MHz and get 46W, another 200MHz gets 34W, and at 800MHz a mere 13W. Given that the new Prescott-core Pentium 4's burns well north of 100W, this is pretty neat. Note that since AMD's transistors have a MUCH lower leakage level than Intel's (20% versus 50%) your idle power consumption at any clock rate is going to be pretty low. Things will get even better when the new 90nm chips come out in a few months.
CRTs can go into power-saving as well. Did you think about doing that? I have a "Kill-a-Watt" power meter, and I measured the power used by my NEC CRT monitor in power saving mode. When it first goes black, it drops from 70 watts down to like 10 watts. When it goes all the way into full power-saving mode where it turns off the tube, the power usage drops down to around 1 watt.
So, I think it's safe to say that when CRTs go into power-saving mode, they also use almost nothing.
However, they *do* use more while running, there is no question about that. My 21" uses some ungodly amount of power. I've forgotten now, but I think it was well over 100 watts.
I was on a quest to quiet down the PCs I've got, and came across the Seasonic Super Tornado Review over at SilentPCReview.
.98 to .99. I used a Kill-A-Watt meter to measure before/after power draw and PF. The PSUs replaced were 2 generic PSUs and one Antec True Power unit.
I measured the before and after current draw of my PCs and found that the Seasonic Super Tornado PSUs were not only much quieter than the PSUs I replaced, but also reduced current draw out of the wall about 15%. Additionally, they have a PF that I measured at
The Seasonic PSUs are the most efficient that SilentPCReview has reviewed at about 80%. It makes sense that if you are building a new PC or need to replace a failed unit to spend the money on the Seasonic units. They are even competitively priced compared to other name brand PSUs as well.
In fact, to efficiently do DC->DC, most circuits actually do DC->AC->DC, again using a transformer to do the voltage step-up-down. A transformer is the most efficient way of doing voltage conversion (really impedence matching), at least when moderate to large amounts of power are involved, and transformers require AC to work.
Your electric meter tells how many kilowatt hours you consume. The same meter with the help of a clock that measures seconds and some simple math can show you how many watts your appliances use. The disk that rotates in your meter has a black reference mark. On the dial plate, usually in the lower right, is a conversion factor for that particular meter (for example Kh=7.2). To read watts, start counting seconds and disk rotations when you see the mark. Stop counting after a minute or after several disk rotations. The formula is watts = (Kh x number of disk rotations x 3600) / number of seconds. For example, you count 5 rotations in 64 seconds (7.2 x 5 x 3600) / 64 = 2025 watts. You can measure your whole home consumption or you can turn everything off and measure one appliance at a time. You may be surprised to see your meter turning when every appliance, including your refrigerator, is turned off. That's because "phantom loads," devices that are on even when you turn them off are still using power. Televisions, phones and answering machines with "power cubes," VCRs, etc. are some phantom loads.
I tried this and found over 200W of phantom loads!!!
Yes! Although it might seem obvious, I'm glad you pointed out the benefit of LCD monitors being MUCH easier to move around. The last time I worked in corporate I.T., everyone was in the process of upgrading from their old 15" monitors to 17" models, and some people were starting to justify 19" and 21" models for specific needs.
The larger screens were great, except lugging them from a basement across the street to the other building, and then upstairs to the 2nd. floor got to be quite a chore. There was always the very real risk of someone accidently slipping and falling, smashing an expensive new monitor, or even injuring someone if it was, for example, dropped down a flight of stairs.
Perhaps more of an immediate problem were the shipping costs. We had several locations supported from a corporate HQ building, and the cost to ship a 17" or 19" monitor back and forth between locations a couple times probably made up for the price difference of going with an LCD instead.
Also, I remember some people putting up with their old 14" or 15" CRT only because they had such a limited space to work with. Since a 15" LCD panel gives pretty much equivalent screen real-estate to a 17" CRT, they'd have much more usability in spreadsheets and the like without taking up any more space on their desk at all.
What you're describing is linear regulation, and is the most basic type of power supply normally made. It's also horrifically inefficient, not because of the transformer or bridge rectification, but because the voltage regulators use transistors operating in the linear mode (hence the term "linear regulator"). If you understand basic electronics, you can think of the transistor as an adjustable resistor; it has to create a voltage drop between the output of the bridge rectifier and the output voltage. So of course, that transistor consumes power (given off as heat); the more current the load demands, the more current goes through that transistor, and the more heat it produces. Obviously, you want to keep the bridge voltage as close to the output voltage as possible, but there has to be a certain differential because of filtering etc.
Aside from the inefficiency of the linear regulation, the other big problems with this kind of supply are size/weight (because of the huge transformer), losses in the transformer itself, and the need to have a large heatsink on the regulator.
Lastly, transformers don't make computer power supplies inefficient or heavy, because they don't have them. Computer PSs use switching power supplies, which have capacitors, inductors, and transistors (operated in the highly efficient saturation (full-on) mode), and are much more efficient than the linear power supplies you referred to. However, the efficiency of switchers can vary greatly, which is what this article is all about. Well-designed switchers can be extremely efficient (like over 90%), but commonplace PC power supplies are much less efficient due to poor design and construction, which is no surprise since most people and companies buy the cheapest stuff they can.
Maybe you need a refresher on how to divide numbers. In 1994, as I've already shown, the U.S. alone emitted about 1.3 billion tons. The paper the parent poster linked to shows CO2 emissions from the biggest volcanic sources. They add to about 1 billion tons.
So in fact, the U.S. is emitting about 30% more CO2 per year than all the most active volcanic and geothermal areas combined. Worldwide human emissions are even greater.
I have a wife & todler and live in a 5 room apt (2 br, 1 bath, kitchen & living/dining room) and we use very little power. Granted we don't have a washer, drier, water heater, or electric heat. But we pay attention to our power use.
1) our tv (27")& dvd/vcr is on an outlet run by a light switch. TV's have instant on where they are charging the capacitors all the time. ITs not like the old B&W tv's that had to warm up. Also, the vcr drains power displaying the time and what ever else it needs to do.
2) The computer stays on most of the day (7ish - 11ish), its a 200w pwr supply and I've got a raid 0+1 on 4 drives. the 21" monitor which is an IDEK iiyama from circa 1992 is turned off when we are not using it. If we leave the house for a few hours we will pwr down the computer and flip the surge protector and turn off the wap, cablemodem, printers(if on), and speakers.
3) we use the toaster oven & microwave more than the regular oven & stove top. They use way less energy. If I'm only heating up some french fries and dinner rolls it takes less to heat up a small toaster oven that a large stove. The fridge we can't do much about, its ancient, we just don't open it more than we have to. THe more it's opened the more it has to cool back down.
3) lights, we have energy efficient bulbs, they cost $0.39 each after the rebates from effiency vermont. We turn them off when we are not in the room.
4) We only have one clock that is plugged into an outlet, the other clocks in the house are battery operated and the battery will last 2+ years.
5) we unplug the wallwart for anything we it is not being charged/used.
The only things that may be left in to suck power when not in use is a radio down stairs and the one in my daughters room that we leave on at night for her.
6) the a/c in the summer time, I've insulated as best as possible around the window it sits in. I ahve it on a timer, it only comes on at night in my daughter's room to help keep her cool. It's on from 7- 12, by that time it's cooled off enough and the cold air stays in pretty well. We adjust the shades/blinds to keep as much direct sunlight out of the apartment and from heating it so we don't use fan's very much. Only when it is above 80 degrees.
So less than 200kwh per month is possible for a family and you can still watch a decent size tv & have a computer on all day. Even if we forget to turn something off or unplug something, its not that big of a deal. Plus living in a town that owns it's own electric company, I have never seen a bill for my place over 27$.
~bigmoose