Even with a built in internal dishwasher heater - Running a cold water
pipe to a dishwasher is not advisable. Depending on the model it will
either take excessive time to complete the wash cycle while the water
heats up, or it will just plain not clean the dishes properly.

In a residential situation, usually one big hot water heater is better
than two medium size ones. The point-of-use heaters are more
expensive, trickier to install and adjust, and require venting to the
outside (for the non-electic models). You may find that a single
point-of-use may not be the most economical solution for one
dishwasher.

Beachcomber