Wiki: Wallwart energy use

[Bob Eager]

I expect that one danger factor is the mechanical failure of the casing - leaving one with a handful of live bits....!

[Bob Eager]

Most of my PSUs are very light - they're nearly all switch mode wall warts.

[jkn]

This thread has reminded me: with 'wall warts' in an unswitched socket supplying an appliance, the only way to turn the appliance *truly* off is to unplug the wall wart. I often have several of the beasts plugged into a 4-way extension block, which is also unswitched. As a result they get left on longer than I'd prefer.

What I'd like is some sort of 'switch adapter plate' with a 13Amp socket on one side, a 13A plug on the other, and just an on-off mains switch built into the plate.

I can see all sorts of resons why these migh not be made - but has anyone seen anything like this?

Ta J^n

[Andy Burns]

It'd have to be pretty thick to accommodate the pins on the plug, probably about the size of a double adapter, you /can/ get switched versions of those, but why not replace the plug on the 4-way with one like this?

[Dave Liquorice]

You can get multiway socket adapter blocks where each of the the three outlets has an individual switch. But one may as well just swap your unswitched 4 way extension block to one with individual switches.

[jkn]

attempted rearrangement, only *some* of the sockets on the extension are appropriate to be switched off.

Years ago, as a kid, I built an extension block with individual switched outlets (I think I wanted a *5*-way one for the hifi I was building). As Dave Liquorice says, I could get one of those again. They tend to be a bit pricey though...

Jon N

[John Rumm]

Would it not be easier to just change the socket for a switched one?

You can get remote control plug in switches to make turning stuff on or off easy.

[jkn]

replying to myself...

[jgharston]

[Andy Burns]

bet about half of all wallwarts would foul the switches anyway

[Bob Eager]

I have two six way strips, mostly populated with wall warts. No switch fouling so far...

[<me9]

What I've been looking for for some time but not found is a switched extension without neon indicators. The red lights are a nuisance in the bedroom.

[The Natural Philosopher]

Years ago I made one from surface mount boxes and standard switched faceplates.

It outlasted several ready made ones..

[Tabby]

Ready made they are, I always made them from left over or even discarded sockets.

NT

[Dave Liquorice]

Nothing a pair of snips or a bit of black tape wouldn't cure...

[Dave Liquorice]

I have a similar one for the "charging station" also stuffed with wall warts, no switch fouling.

[John Rumm]

Saw 4 and 6 way versions in Tesco about a couple of hours ago. The most expensive was £7 but that may have been the surge suppressed version. Most were under £5.

[Andy Burns]

Several of mine barely fit onto a strip adjacent to each other, they do tend to be the older, heaver, hotter-running ones, suppose I could rescue some suitable switchmode replacements from a skip ...

[Bob Eager]

CPC have loads of switched extensions - I have several of the 6 way ones.

Some have only one neon, and that's easily fixed with tape, or a more permanent solution...

[Tabby]

Latest version. Have added some more calculation data, a new section on efficiency and some more links.

NT

[[Wallwart]]s are little plug-in power supplies that power small appliances. They're often maligned for wasting power, due to often being left always on, and having some quiescent power use and less than perfect efficiency. A fact based assessment can clarify the truth of the situation.

[[Wallwart|Main Wallwart article]]

=3D=3DSearch words=3D=3D PSU, power supply, wall wart

=3D=3DFigures=3D=3D

I once had 5 minutes to wait and did a wallwart survey on an average 3 bed house with gas heating. The things I do.

Annual electricity spend: apx =A3600

Wallwart count:

• Bedroom 1: mobile, laptop, mini fan

• Bedroom 2: mobile

• Bedroom 3: 2 mobiles, pc speakers

• Lounge: 0

• Kitchen: 0

• Bathroom: 0

• Other: mini tv, preamp, laptop, broadband modem

Bed 1:

• mobile: 1 hr twice a week, apx 4w waste =3D 8wh/wk

• laptop: 0.5hr/day, apx 10w waste =3D 35wh/wk

• fan: 14 hrs/day for 6 months a year 3w =3D 21wh/wk

Bed 2:

• mobile: 1 hr 2x a week, apx 4w waste =3D 8wh/wk

Bed 3:

• 2 mobiles, 1 hr 2/week each, apx 4w waste =3D 16wh/wk

• 1 pc speaker: 3hrs/day, apx 3w waste =3D 63wh/wk

Other:

• mini tv: 24/7 2w waste off, 10w on. on 2hrs/day

• =3D 64 wh/day =3D 448wh/wk

• preamp: 24/7 apx 2w waste =3D 336/wk

• cable modem 24/7 apx 5w =3D 868wh/wk

• laptop 1hr/week @ 10w waste =3D 10wh/wk

So total estimated power losses:

• Bed 1 106 wh/wk =3D 5.5 kWh pa

• Bed 2 8 =3D 0.4

• Bed 3 79 =3D 4.1

• Other 1662 =3D 86.4 kWh pa

Annual total is 96.4 kWh pa.

• At 10p/unit thats =A39.64

• And annual spend is =A3600 pa

so '''Percentage of electricity wasted by wallwarts is apx 1.6%'''

For electrically heated houses the percentage is much smaller, since annual electricity spend is much higher.

=3D=3DSwitching off=3D=3D What would happen if one went round the house turning them all off when not needed?

• Bed 1 use would not be any less

• Bed 2 use would not be any less

• Bed 3 use would not be any less

• mini tv saving: 22hrs 2w =3D 44wh/day =3D 308 wh/wk

• preamp saving: 23hrs 2w =3D 46wh/day =3D 322 wh/wk

• modem saving: 20hrs 5w =3D 100wh/day =3D 700 wh/wk

Total possible electricity saving 1.33kWh/week =3D 69kWh pa =3D =A36.90 per annum.

However the heat this wasted power gives off has value in winter. In an electrically heated house (storage heaters) the annual saving will be halved for 8 months a year, and full for 4 months in summer. Saving is thus:

8/12 x .5 + 4/12 x 1 =3D 2/3 the above figure =3D =A34.60 per year

In a gas heated house, saving is about 2/3 the above figure in winter, and 100% of it in summer

8/12 x 2/3 + 4/12 x 1 =3D 0.777 x above figure =3D =A35.37 per annum

'''So by going round turning them off every time all year long you can save about =A35 a year.''' Would it be worthwhile? Lets estimate 4 times a day, ave 30 secs each =3D 2 mins a day switching them off. That's 12 hours a year =3D '''41p an hour''' payback for the labour of switching wallwarts off.

=3D=3DWhat if we got rid of warts=3D=3D

Getting rid of [[Wallwart|warts]] at the product design stage would mean incorporating the small power supply into the appliance itself, rather than it being external. The parts and function of that supply would be the same, in other words there would be no energy gain of any kind by eliminating external warts. The energy use would simply move from one location to another, from outside the appliance to inside.

=3D=3DAccuracy=3D=3D

The figures are for a fairly typical household, but of course changing patterns of use do cause some variation.

The power waste figures were typical inefficiency estimates rather than individually measured. However this is plenty good enough to demonstrate the nature of the situation.

=3D=3DWart efficiency=3D=3D The efficiency of warts varies a fair bit, but often they aren't marked with enough data to determine efficiency without resorting to testing.

As a general rule of thumb:

• Modern lightweight switched mode warts are often very efficient

• Lump of iron type warts have moderate efficiency

• Some of the early switched mode warts (from 2000 or so) can have poor efficiency and run hot

Energy loss always shows up as heat. So relative power loss is the case temperature rise above ambient multiplied by the case's surface area. So in simple terms check how hot they are; stone cold warts are very efficient, hot warts are inefficient. If a wart doesn't even get warm, power loss is as good as zero.

=3D=3DBenefits of warts=3D=3D

Compared with using internal supplies in appliances, which is currently the only other mass workable option, [[wallwart]]s give the following benefits:

• Smaller lighter appliances

• The cost and production energy use of a [[Flex|mains lead]] is replaced with those of a length of thin [[Low Voltage Wiring|speaker wire]]

• No need to design, test or certify the appliance to mains safety requirements: cuts design time, costs, material use, and the legal & paperwork costs of certification

• Removal of the power supply's heat from appliance extends the life expectancy of small appliances to a limited degree

• Use of external power supplies makes it practical to use the appliance in another country with another mains voltage or frequency

• An external supply makes one appliance model exportable to all countries, reducing business costs

• Mass produced warts can be imported cheaply, offsetting design & build costs for British goods

• A failed power supply is easy to replace, the more expensive appliance is still good.

=3D=3DDownside of warts=3D=3D

• Use of the wrong wart can in some cases kill an appliance

• Not known for their beauty

=3D=3DSee Also=3D=3D

• [[Wallwart]]

• [[Special:Allpages|Wiki Contents]]

• [[Special:Categories|Wiki Subject Categories]]

[[Category:Electrical]]

[[Category:Energy Efficiency]] [[Category:Appliances]] [[Category:Low Voltage]] [[Category:Save Money]]