# Unconnected wall wart power consumption

• Electrical
• noname12345
In summary, the conversation discusses the power consumption of a phone charger when it is plugged in but not connected to a device. It is mentioned that newer wall warts are more efficient and do not use much power when not in use. The speakers also discuss the limitations of calculating the power consumption due to potential control and communication circuitry. It is suggested to use a wattmeter to accurately measure the power consumption. The conversation also touches on the topic of fast chargers and their control circuitry.
cmb said:
Is there some solid, certified published reference for this?
No I can't find a good reference, so you may be right it could be a guess or a legend. Let's try to estimate it ourselves for the year 2001.
1. 15 w per wall wart x 24 hours
2. standby power 30 w per TV or stereo for 24 hours
3. Let's say 5 wall warts plus 3 TV/stereo per household.
5. Say 100M households, but only 75M affluent enough for so many devices.
6. 75M * 4 kWh/day = 300M kWh/day, 300M*365 = 109 billion kWh/year.
7. Reliable source https://www.eia.gov/totalenergy/data/monthly/pdf/sec7_2.pdf Shows total generation in 2001 at about 3500 billion kWh/year.
8. 109/3500 = 3%
[Please check me. It's so easy to slip decimal points.]

So my estimate is only half of the 6% number. But it is in the same order of magnitude, and for a back-of-the-envelope guess, not bad.

[I used the strange units "billion kWh/year" to make it easy to compare with my source.]

Now, think of 2021. My wife and I have 5 digital devices @0.1 watts, + (1 TV + 2 laptop) @2 watts. That is 6.5 watts wasted on standby power compared to 165 watts in 2001. The difference is major.

15W loss per wall wart!? Phew. Those would be very hot wall warts (or very powerful ones)!

I think most are a few watts at full load! Assume 10% losses, maybe half a watt each?

Most modern LED TVs are also 50~100W or so while on. Maybe an old CRT might have used 10's of W to keep things 'warm'? Again maybe a watt or two to keep the remote control circuits alive and a watt or so in the (unloaded) power converter.

If we're multiplying up 'a number' by 100 million, I think the detail needs to be improved on, whichever way the estimate goes. Small changes but times 100 million will give you big differences on that %age conclusion.

russ_watters
I always found 6% hard to believe also. If you look around there are many many things that seem a lot more wasteful than that. I find drying clothes in a dryer to be bad. At my house most things get hung. In the winter the moisture is a bonus. Any extra heat needed at least doesn't go out the dryer vent.

My old Motorola 6200 set top box says 40W on the back. When I first installed it, it fit neatly in the cabinet on top of my amp. Until I touched it, ouch, hot! I found this comment from 2009:
Since it's a STB, why not simply leave it on all the time. There's very little difference in power consumption between on/off on a STB (off is really standby).

Keith_McClary said:
Old folks have big boxes of those, with various voltage, wattage and connectors (but never the combination they need).
Edit: Oh, and I forgot polarity.
Your right! I'm in my sixties and I have two boxes of them and a neat universal adapter that had attachments for different connector plugs and polarities. Unfortunately I moved recently and can't find the box with the attachments. A while back (10 years?) my electrical engineer brother was grousing about the wasted electricity.

My question is, how much energy would be saved if you have solar panels and could have inside wiring to have DC wall plugs. It seems to me a waste to have a transformer to make solar power into AC and then have to transform it back again to DC.

Welcome to PF.

Lrodcepts said:
My question is, how much energy would be saved if you have solar panels and could have inside wiring to have DC wall plugs. It seems to me a waste to have a transformer to make solar power into AC and then have to transform it back again to DC.
Well, for efficient moderate-size PV installations, you are already using switching power conversion for MPPT:

https://en.wikipedia.org/wiki/Maximum_power_point_tracking

So to chop it to AC Mains levels will not be that different in efficiency compared to 12Vdc, IMO. Have you learned about MPPT converters yet, and why they are used with PV panels?

Lrodcepts said:
My question is, how much energy would be saved if you have solar panels and could have inside wiring to have DC wall plugs. It seems to me a waste to have a transformer to make solar power into AC and then have to transform it back again to DC.
Physical switches do not work well in inductive DC circuits. They tend to set fire to the house. We need the AC so we can switch it off.

berkeman and anorlunda

Replies
7
Views
1K
Replies
2
Views
2K
Replies
39
Views
10K
Replies
4
Views
2K
Replies
6
Views
1K
Replies
5
Views
1K
Replies
2
Views
3K
Replies
2
Views
1K
Replies
31
Views
3K
Replies
8
Views
1K