[Amps] Autotransformer

[Angel Vilaseca]

Hi,

I have a nice 1 KW HV transformer with a 110 V primary.

Unfortunately, mains in the shack is 220 V only.

I also have several unused transformers with a 220 V primary tapped for 
110 V.

So I was thinking of using one of these transformers as an 
auto-transformer to feed the HV one.

My question is: does the auto-transformer have to be a 1 KW unit, or can 
it be less than that?

Vy 73

Angel Vilaseca HB9SLV