“Do USB Chargers Use Electricity When Not Charging a Device?”
If you’ve ever left your phone charger plugged in after your device is fully charged, you may have wondered whether the charger is still using electricity. The answer is YES, it consumes power no matter the device is connected or not. Most USB chargers will still consume a small amount of electricity even when they are not charging anything. This is known as standby power.
Below is a typical example of the circuit design for phone charger.
The basic charging circuit would normally include three main functional parts – Transformer (for stepping down voltage), Rectifier (for converting AC to DC), Filter (for smoothing DC flow).
When the charger is plugged in, the first component in the circuit is a transformer that reduces the voltage of the AC power source. When there is no device connected to the other end, there will be no current flowing in the circuit besides the primary winding of the transformer. However, there will still be a small amount of power consumption due to the current flowing in the primary winding of the transformer as long as the power supply is on.
How much standby power do USB chargers actually use
But how much standby power do USB chargers actually use? The amount of standby power consumed by a charger can vary depending on the specific model, but it is typically a very small amount, on the order of a few watts. To put that into perspective, The average electricity consumption of an Australian household is about 18 kilowatt-hours per day, which is about 0.75 kilowatt-hours per hour, so the standby power consumed by a charger is just a drop in the bucket in comparison. However, if you have a few those chargers, it would still save you somewhere between 30 and 80 dollars a year on your electricity bill by turning off them when not using.
But if we count the electricity transmission loss on the grid, and the amount of resource waste in the power generation process, this small standby power could amount to much larger problem.
As electricity flows through the transmission and distribution networks, energy is lost due to electrical resistance and the heating of conductors. The losses are currently equivalent to approximately 10% of the total electricity transported between power stations and market customers, according to AEMO (Australian Energy Market Operator). The small standby power waste in each household would now equal to 111% at the start of the grid.
Let’s also look at the power generation process. Power plant generation efficiency refers to the percentage of the energy contained in the fuel that is converted into usable electricity by the power plant. The efficiency of a power plant can vary based on the type of plant and the type of fuel being used. The recorded average efficiencies for some of the power plants are:
· Coal-fired power plant — around 33%
· Natural gas-fired power plant — around 44%
· Nuclear power plants — ranging from about 33% to over 50%
· Solar photovoltaic panels: 15-20%
· Wind turbines: 30-45%
· Hydroelectric dams: 80-90%
· Geothermal power plants: 10-15% for dry steam plants, 40-45% for flash steam plants, and 60-70% for binary cycle plants
· Biomass power plants: 15-25%
At the start of the process, the standby power waste on our desk, however small, would amount to nearly 3 times of the resource waste.
Why should you still care
More importantly, the environmental impact of standby power shouldn’t be overlooked. While the amount of electricity consumed by a single charger may be small, the collective impact of standby power on our electricity grid is significant. In Australia, standby power, also known as vampire power or phantom load, is estimated to account for about 10% of total residential electricity consumption, according to Australian government energy rating website. That may not sound like a lot, but it adds up to billions of kilowatt hours of electricity each year – and all of that electricity has to come from somewhere.
The production of electricity is a major contributor to greenhouse gas emissions, and over half of electricity in the Australia is still generated from fossil fuels like coal and natural gas. This means that the standby power consumed by our chargers and other electronic devices is contributing to climate change.
Make it count
It’s understandable that most people think the convenience of leaving it plugged in and switched on outweighs the small waste, after all the 50 dollars a year won’t break the bank.
However, if you’re really trying to reduce your energy consumption or if you’re concerned about the environmental impact of standby power, then go ahead and turn off or unplug your charger when it’s not in use. Every little bit helps when it comes to fighting climate change.
