SylvanLMP
Tom your better off with installing a return circulation line rather than a point of use heater.
I installed a point of use heater on a 6 story one family building only because the water was to supply one basin until the building H/W reached this point.
The problem with under the sink heaters is volume. You may not have enough volume for a complete cycle of washing/rinsing.
Another factor is flow rate Vs make up time and demand.
I have installed several 220-440 Volt instantaneous heaters/boosters just for dishwasher applications but again this may be over kill for a one family home.
Have you also considered a new product from NIBCO called just right for circulation of H/W
Good luck
