: I am building a house, and I am thinking about putting a on demand hot water heater in... Only thing that I am curious about is how much the difference in water pressure it is going to be... If anyone has any experience, or knowledge about these, would appreciate any, and all comments...

: Thanks

On Demand gas water heaters only put out so much water at time. You will need to check the specs to see how many gallons per minute they can do.
If you want heated water in several places in the home, you may need several "on demand" heaters.
Before gas prices went up last Winter, you could heat all the water for a family of four for about $180 per year with a 50 gallon, 40,000 BTU water heater. That's not that much money.