The transformers are small in comparison, which gives poor
regulation in comparison (and as I said before, it's the
regulation at 120V which is the primary concern -- regulation
of 240V across 2 hots doesn't matter much for typical US 240V
loads).



Regardless, the regulation is very good. I monitored mine for a while
and never saw it dip below 118V or go above 122V, most of the time it
was just about spot on 120V. A friend in the UK was doing the same on
his and it went as low as 224V and as high as 246V. We've done a lot of
comparing and have agreed that neither system is inherently better or
worse than the other, both have advantages and disadvantages.