Hi Gene. Things to consider: Do you prefer gas or electric? More heating btu's are available from gas, which means more hot water is produced by gas units. Having said that, a 28kw electric heater is 95,564btu's! That's a lot of heating ability. We have gas units up to 235,000btu's, that's over 7gpm of hot water (three simultaneous showers) depending on your cold water temp. Electric units need additional wiring, and at least a 200amp service. My personal preference is for gas units (even though I'm an electrician). I don't know if you are building a new home, or just changing out heaters. Do you have gas or electric now? If you have gas, go with gas. I need to know more, before I can make a recommendation. The best whole-house electric unit for the money, is Seisco, and for point-of-use, the G.E. Powerstream is great, I sell both, and deliver all over the world. I also sell the two best gas units available, which are Bosch (featured several times on Bob's shows) and Takagi. Takagi makes three incredible, sealed-combustion, power-vented units, 165, 185 & 235,000btu's. I won't trash anyone elses heaters in public, but there are instant heaters out there, which I have used/sold/installed, and will never use again. My e-mail is email@example.com & my Ph no. is 800 851 9891, during sensible working hours :o) central time. I hope this helped some. Regards from Brian, in rainy, muggy swampland.