Difference between revisions of "Wallwart energy use"
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[[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. | [[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. | ||
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==Figures== | ==Figures== | ||
| − | I once had 5 minutes to wait and did a wallwart survey on an average 3 bed house with gas heating. | + | 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. |
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| − | The power waste figures were typical inefficiency estimates rather than individually measured. However this is plenty good enough to | + | The power waste figures were typical inefficiency estimates rather than individually measured. However this is plenty good enough to demonstrate the situation. |
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==Benefits of warts== | ==Benefits of warts== | ||
| − | Compared with using internal supplies in appliances, which is currently the only other mass workable option, [[wallwart]]s give | + | 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 | * smaller lighter appliances | ||
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* the cost and production energy use of a mains lead is replaced with those of a length of thin speaker wire | * 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 | + | * 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 heat source from appliance extends the life expectancy of small appliances to a limited degree | * removal of the power supply heat source from appliance extends the life expectancy of small appliances to a limited degree | ||
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* use of external power supplies makes it practical to use the appliance in another country with another mains voltage or frequency | * 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 | + | * 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 | ||
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| + | * a failed power supply is easy to replace, the more expensive appliance is still good. | ||
| + | ==Downside of warts== | ||
| + | * Use of the wrong wart can in some cases kill an appliance | ||
| + | * not known for their beauty | ||
Revision as of 09:05, 25 October 2010
Wallwart energy use
Wallwarts 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
Figures
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 £600
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 = 8wh/wk
- laptop: 0.5hr/day, apx 10w waste = 35wh/wk
- fan: 14 hrs/day for 6 months a year 3w = 21wh/wk
Bed 2:
- mobile: 1 hr 2x a week, apx 4w waste = 8wh/wk
Bed 3:
- 2 mobiles, 1 hr 2/week each, apx 4w waste = 16wh/wk
- 1 pc speaker: 3hrs/day, apx 3w waste = 63wh/wk
Other:
- mini tv: 24/7 2w waste off, 10w on. on 2hrs/day
- = 64 wh/day = 448wh/wk
- preamp: 24/7 apx 2w waste = 336/wk
- cable modem 24/7 apx 5w = 868wh/wk
- laptop 1hr/week @ 10w waste = 10wh/wk
So total estimated power losses:
- Bed 1 106 wh/wk = 5.5 kWh pa
- Bed 2 8 = 0.4
- Bed 3 79 = 4.1
- Other 1662 = 86.4 kWh pa
Annual total is 96.4 kWh pa.
- At 10p/unit thats £9.64
- And annual spend is £600 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.
Switching off
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 = 44wh/day = 308 wh/wk
- preamp saving: 23hrs 2w = 46wh/day = 322 wh/wk
- modem saving: 20hrs 5w = 100wh/day = 700 wh/wk
Total possible saving 1.33kWh/week = 69kWh pa = £6.90 per annum.
You can save about £6.90 by going round turning them off every time all year - would it be worthwhile? Lets estimate 4 times a day, ave 30 secs each = 2 mins a day = 12 hours a year = 57p an hour.
What if we got rid of warts
Getting rid of 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.
Figures
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 demonstrate the situation.
Benefits of warts
Compared with using internal supplies in appliances, which is currently the only other mass workable option, wallwarts give 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, 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 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 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.
Downside of warts
- Use of the wrong wart can in some cases kill an appliance
- not known for their beauty