At the time of Edison, they already had AC transformers that made AC voltage conversions either up or down very easy. All you need is an iron ring, and you wrap some wire around it.<p><a href="https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Transformer#&#x2F;media&#x2F;File:Transformer3d_col3.svg" rel="nofollow">https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Transformer#&#x2F;media&#x2F;File:Transf...</a><p>DC transformers only recently reached comparable performance, thanks to semiconductors, and efficiencies are not as high as a good AC converter without really sophisticated circuits.