Well, 215 mW may not sound like a lot, but with all the commotion about standby power consumption of household electronics (aka vampire power aka phantom power), an extra 215 mW continuous for your energy measurement device seems like a lot to me. Once again, poor engineering. All it needs is a tiny MCU (less than 30 mW) and an ADC (a few mW) as well as a segmented LCD driver (less than 1 mW).

Haha! All it needs is the owner to use one of those 6in1 power boards that has ON/OFF SWITCHES.

I have one with a few chargers plugged into it. It's no effort at all to flip the power switch when I plug in the cellphone...

And my little DCSS brand mains power measuring device has 2 button cell batteries in it powering the brain LCD and memory, and draws zero power from the mains, apart from maybe a couple uA for the mains voltage measuring which is guess is a resistor in the megohms.

 

Hi....,
Actually, there will be a closed loop in the charger circuit. So the current passes in that loop even without cell phone is connected. then some power consumption occurs.

 

Most cell chargers are just flyback smps so yeah, still sucking power

 

And my little DCSS brand mains power measuring device has 2 button cell batteries in it powering the brain LCD and memory, and draws zero power from the mains, apart from maybe a couple uA for the mains voltage measuring which is guess is a resistor in the megohms.

Great idea in theory to use batteries, but the energy to produce them is probably more than would ever be used by the device if connected to the mains.

 

Great idea in theory to use batteries, but the energy to produce them is probably more than would ever be used by the device if connected to the mains.

I don't know about that. At least, not if the usual inefficient power supply is used.

Designing for batteries will force the product designer to make a power-efficient product, so that is another side-effect. If it's on mains power then there is little incentive to the manufacturer to make it efficient.

Battery power may enable some other features as well such as persistence of stats when the device is unplugged and recording of power outage event durations, etc.

 

Yeah it has the ability to record average power use of a device over time and total accumulated power use of a device, so the battery would enable say a monthly total even if there was a blackout at some point. I've seen them in a few shops for about $30.

But I agree with Tom66, the cost of batteries and environmental issues of battery manufacture, mining and disposal etc probably adds up...