Didier Stevens

Saturday 8 October 2022

Quickpost: Standby Power Consumption Of An Old Linear Power Supply

Filed under: Hardware,Quickpost — Didier Stevens @ 11:41

In my blog post “Quickpost: Standby Power Consumption Of My USB Chargers (120V vs 230V)“, I looked at the power consumption of several of my USB chargers in standby mode (e.g., not connected to a device to be charged).

These are switched-mode power supplies.

They consume considerably less standby power than linear power supplies, like this one:

These contain a transformer to go from a high voltage (AC) to a low voltage (AC), and then contain some electronic components, for example a diode bridge and capacitors, to convert the low voltage AC electricity into DC.

I tested this old power supply I had lying around, and it consumed 1.6836 Wh when tested with my power meter during one hour:

That’s 14,75 kWh for a year. Which is about 10 times more than my worst switched power supply tested here.

So, if you are planning to follow the advice of energy experts here in Europe (and watch out, quite a few are not experts at all, just echo chambers) to reduce your electric energy consumption and save money, consider the following points (their idea is to unplug chargers you don’t use).

  1. Start with your linear power supplies, they consume the most (a tip to recognize them: they are heavy compared to the switched-mode ones, because of the transformer; and they are old)
  2. If you are going to do this daily, take into account mechanical wear and tear. Like on the pins of the power plug, the cables …
  3. To avoid that extra wear and tear, you can plug your power supplies into a power-strip with a switch
  4. I have a laptop power brick that regularly cause the power plug to spark when I plug it into a socket. That’s also something you want to avoid.

Quickpost info

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