Wiki: Wallwart energy use

[Tabby]

Feedback welcomed...

NT

[[Wallwart]]s are often maligned for wasting power, due to often being left always on, and having some quiescent power use plus less than perfect efficiency. A fact based assessment can clarify the truth of the situation.

Main [[Wallwart article|Wallwart]]

=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. Strange 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 saving 1.33kWh/week =3D 69kWh pa =3D =A36.90 per annum.

You can save about =A36.90 by going round turning them off every time all year - would it be worthwhile? Lets estimate 4 times a day, ave 30 secs each =3D 2 mins a day =3D 12 hours a year =3D 57p an hour.

=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=3DFigures=3D=3D

Figures are fairly typical for the average household, but of course changing patterns of use will cause some variation.

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

=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 us the following benefits:

• smaller lighter appliances

• the cost and production energy use of a mains lead is replaced with those of a length of thin speaker wire

• no need to design or test the appliance to mains safety requirements, cuts design time, costs & material use

• removal of the power supply heat source 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 model exportable to all countries, reducing business costs

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

• [[Wallwart]]

• [[Special:Allpages|Wiki Contents]]

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

[[Category:Electrical]]

[[Category:Energy]]

[The Natural Philosopher]

One very useful number is that every continuous watt is a pound a year, based on 10,000 hours in a year and 10p/KWh.

So a 300 pound appliance that saves 100W average pays for itself in 3 years.

Another useful number is that a liter of oil is about 10 units of electricity, when comparing prices oil v electric.

[chrisj.doran]

An expensive device would have to be repaired professionally or thrown out if the power supply failed.

and conversely:

• If the wart fails, you still have the expensive bit.

A potential disadvantage is the risk of blowing up said expensive bit by using the wrong voltage/polarity/(un)stablised/ACvsDC wart by the non-technician who doesn't appreciate the differences, or the tired technician with several different ones stacked together in a dark place.

Chris

[Andy Burns]

Original message didn't show up here ...

You probably covered the reasons why wallwarts (do you have to call them that?) are used in the first place ...

• Ease of certification (CE, UL etc) of the product by moving the PSU to be external

• Producing a single product and then just supplying various PSUs for different markets (various voltage/frequency/plug standards) though now the wallwarts tend to accept anything from 90-260v,50/60Hz anyway.

• Separately outsourcing to cheap far-east PSU manufacturers, even if the appliance manufacture isn't outsourced.

[Tabby]

More points incorporated, thanks everynoe

NT

[John Rumm]

I would include a "proper" name in the tile as well for folks who want to search for power supply or PSU etc.

You need to differentiate between older style linear supplies and switched mode ones. The switchers have a negligible current draw when plugged in but not connected to their equipment - so the "waste" is almost non existent.

[Dave Liquorice]

I don't mind approximations when they are reasonably close but 10,000 hrs in a year is pushing it bit too far IMHO. 365 * 24 =3D 8760...

Make the units cost 12p/unit, which isn't that far from the average these days(*), and it's better. 8760/1000 =3D 8.76kWHr @ =A30.12 =3D =A3=

1.05.

(*) I pay 9. but that is about the cheapest I can get.

[The Natural Philosopher]

heck this is just basic back of envelope nearest power of ten type stuff.

Anyway £1 per watt per year is not a bad scribble factor.

So you want to look at anything much over 50W continuous..and forget maybe anything less than 5W continuous.

[Grimly Curmudgeon]

We were somewhere around Barstow, on the edge of the desert, when the drugs began to take hold. I remember Tabby saying something like:

I'll bet the saving's much higher in the real typical household, where the damn things are never unplugged/switched off.

[Andy Burns]

Isn't he assuming 20 to 23 hours of standby usage per day as it is, so 1 to 4 hours of actual use, savings can't get that much higher ...

[PeterC]

Re. cheap ones, is it worth a note to warn of the unbranded /very/ cheap 'n' nasty ones that catch fire/explode/give shocks/fall apart?

[Tabby]

a) How would you determine which ones will do that? b) For electrocutions, wallwarts aren't a significant cause of electrical fatalities. (For fires we dont have the data.)

NT

[Tabby]

Yup, though its not an assumption fwiw.

NT

[Tabby]

I'll include those points later. But to be accurate, the electronic ones vary in efficiency widely, I've got a couple that have always run fairly hot, even on no load they're very warm. And a couple of thoers that run stone cold even on max output.

NT

[Tim Streater]

[snip figures]

I don't think there's any point in including the extra anal option (i.e., turning all things off when not needed). It's too unlikely to happen. I think your comparison figures should be:

1) That set of wallwarts used 24 x 7 2) That set of figures you have given (snipped above), which is what can be reasonably done if you can get them gathered together in each room, and plugged into a strip where each socket is switched individually. 3) Annual overall consumption.

In practice, (1) is what happens in most houses. The question is, is (2) worth going for? That's going to depend on individuals' situations. E.g. TNP with IIRC 550W of background (WTF!!??) what could he achieve? There's other folks here with large amounts of kit that might be unrepresentative, but what about those with a more "normal" set of devices? I'd say that for this Wiki entry to be really useful, there'd need to be various categories of user defined in the article with their figures represented. I think that would be really helpful.

[Tabby]

I wonder if you might have misunderstood what the 57p/hour figure means. Its the money value of the labour involved in switching warts off. It (roughly) applies regardless how many warts one has.

NT

[PeterC]

Agreed, difficult, so a generalised sentence re. market stalls, =

[Tabby]

I bought wallwarts once for 40p retail, the quality was flawless. There are various reasons why things go cheaply, lack of safety isnt the only or even the prime one. The junk is sold both cheaply & expensively.

As for weight, again it has little to do with quality in electronic appliances. Adding weights made of steel/clay/lead etc to create an end user impression is common practice. I dont think we have any useful safety assessment data to pass on to readers.

NT

[Tim Streater]

So are you going to expand your proposed page in the way I suggest or not. I think what you have is a potentially useful page, if expanded.

[Jón Fairbairn]

It's probably worth mentioning as a rule-of-thumb that if a wall wart doesn't get warm, it's power consumption isn't worth worrying about.