Electronic – Do Step-Down Transformers Increase Total Power Consumption

power-consumptionstep-downtransformer

Firstly I am not at all experienced in electrical matters so forgive any wrong terminology.

Here's the situation:
I recently moved out of US to a country that uses 220v. We have a single phase step-down transformer that provides 120v to the entire house. There are a few appliances that we would like to order with the option of either 110 or 220 versions. (220 versions are more expensive)

What I would like to know is, is there an increase in power consumption if I am to run an appliance through the step-down system vs the direct 220 sockets?

eg. 300w food dehydrator 110v version run through transformer vs 300w 220v version plugged into native wall socket

Another way to ask the question would be; Is the total power consumption of a 600w machine run through a step-down transformer 600w? Or is it more?

Thanks for any insight you can provide on this!

Best Answer

For an ideal transformer, power in equals power out: it's 100% efficient.

For a realistic AC line step-down transformer, power in is a little bit more than power out: it's not quite 100% efficient, but it should be close.

Thus, if you plug a 300W load into a step-down transformer (assuming the transformer is rated for more than 300W), expect it to draw a little more, perhaps 325W - 375W depending on quality of construction.

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