Leaving the charging cable in the socket: That’s how much it costs

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Chargers and power supplies consume electricity even when they are not connected to a device such as a cell phone or laptop. Why this is so: As soon as a charger is plugged into the socket, a small closed circuit is established – even if no other electrical device is connected.
In times of inflation and electricity crisis, consumers wonder what the cost of such an idle loss is. The German consumer protection experts at Öko-Test know the answer: they have compiled previous findings and tested them themselves.

External power supplies and chargers placed on the market since April 1, 2020, may not absorb more than 0.1 watts of power when no device is connected, according to EU Ecodesign Regulation 2019/1782. If the maximum output power is 50 watts and more – for example, in laptop power supplies – then 0.21 watts of power dissipation is allowed, explains Öko-Test.

A small calculation: at an electricity price of 0.40 cents/kWh, around 35 cents are lost if a device with a consumption of 0.1 watts is plugged in continuously for an entire year. At 0.21 watts – for example, with a notebook cable – the loss is 73 cents per year.

As early as 2022, the Swiss consumer program “Kassensturz” examined numerous USB charging plugs. The result: on average, most USB charging plugs consumed around 0.05 watts when idle – a cost of 18 cents a year. An adapter from Apple only lost 0.008 watts – a price of 3 cents per year.

Test repeated
The German Öko-Test checked this data: Most power adapters did not even consume 0.1 watts in idle mode, so the power meter display did not even record any consumption and stopped at 0.0 watts.

Broad relief? Not quite, because a new power supply came up with an idle power loss of 1.2 watts during the review, which is more than the EU allows. Such a part would cause annual costs of 4.2 euros. The German magazine then tested an older power supply intended for a lamp. This old power supply caused 3.7 watts in idle mode, corresponding to costs of 13 euros per year.

The advice of German consumer advocates:

Modern charging cables for small devices such as cell phones are designed for low wattages.
The older power supplies, transformers or chargers get, the trickier they become.
Cables for laptops and larger devices should be unplugged.
If the power supply feels warm even though no device is attached, power is being consumed.