A 200K BTU gas tankless verses an electric running on 240vac is about equivalent to a 244A load. Now, the electric is running close to 100%, and the tankless isn't, so maybe closer to 220A equivalent. Unless you go industrial, you probably won't find an electric tankless comparable to one of the more typical gas tankless units...power is power, whether you measure it in BTU or watts. As a result, you either get a much smaller delta T (temperature rise) out of it, or reduced flow. Think hand through the flame of a candle verses a blowtorch - you can achieve the same temp, but you'll have to run it through the candle flame a lot slower than if it were a blowtorch! A typical electric tankless is closer to a candle than a blowtorch! You either need really warm incoming water or a very low flow to make sense of an electric tankless system.