Home energy audit/tankless water heater cost
Hello. I am posting this question here, and in the plumbing forum. We had an energy audit performed in our old house in NJ, and got great advise on how to make our home more energy efficient. It is a 120-year old house with little insulation, so of course that was one of the biggest recommendations, to insulate all over. I have no quarrel with that. Our water heater is really old, and they recommended replacing with a tankless water heater -- two units, in fact, to accommodate our family of five in this house with just under 4,000 square feet of living space in three floors. We have 3.5 baths.
The cost of those units, they said, with installation, was $8,000. That sounds really steep to me. While I sort of believe in the concept of tankless -- it would be great not to heat water you're not using, and nice to have an endless supply of hot water, especially for our jetted tub -- I can't see paying that much.
My questions are, is that a reasonable price for two tankless units, Navien brand, and does a house this size and a family like ours, really need two units? The other alternative is to go with one traditional 75-gallon water heater.
Thanks for your input.
And by the way, the temperature here lately has been around 20 degrees, to give you an idea of our climate.