system because I had a lot of issues with my first tankless (the company went out of business). My tankless is natural gas so I have an exhaust system that vents outside the home.

I installed our current system myself about 6 years ago. It is two tankless heaters installed in parallel that feed a 10 gallon 115V heater (the small heater helps to get more instant hot water and reduces cold water "flashes" that can sometimes happen with NG tankless heaters). I flush the tankless heaters with vinegar about once per year for maintenance. So far so good. Now that we have a good system, the biggest downside is keeping my 17 year old daughter's shower time down.