[jambutty]

You are quite correct Less transformers do not use a solid iron core but I never said they did. They use a laminated soft iron core or the soft iron is powdered and (for want of a better expression) glued together to form a solid block. But there are different grades of soft iron and the better the grade the fewer eddie currents and thus fewer losses, with “MuMetal” being the best and most expensive. I spent some 20 years of my working life at Dynamo & Electrical Services making the darned things from little itty bitty ones less than one inch cube in size to huge beasts weighing in at several hundredweight.

The induced current in a wire is never anywhere near the value of the source current so cancellation is small but it is still evident. And that applies equally to transformers.

The bottom line is that up to 25% of the generated electricity is lost depending on how many times it is transformed from one voltage to another between the generator and the user. At around 5% per transformer and the same for transmission line losses it would only need two transformations from source up to the National Grid level and two down to user level to incur 25% losses.