Our company installs tankless water heaters and i can say from a service tech standpoint they are a pita,
first the heat exhangers need to be flushed once a year, water quality come into play alot with a tankless, if your water is suseptable to scale buildup plan on flushing every year
second if they break down they cost alot more for parts than a conventional water tank,
third they do break down much more frequently than a conventional water tank,
fourth if your on a water meter plan on spending more money running water waiting for the hot water to get to your tap, we typically have to go back and install recirc pumps for the customers which is another cost in itself. A conventional hot water tank stores hot water and copper piping is exellent at conducting heat which is why you dont have to wait long when turning on the taps to get hot water, tankless if not used for a while the pipes get cold, weve had customers that have to run there showers for over a minute before the water gets hot with a tankless
Fifth, they are much more expensive than a conventional water tank and typicall run about 200,000btus while they are running
Dont buy a tankless if you plan on saving money, weve had numerous complaints after “upgrading” customers to the new tankless design, conventional water tanks now have much better insulation R ratings than ever before and are a fraction of the price of a tankless, much less parts to break down conventionals only have a standard gas valve and a burner and thermocouple whereas a tankless has a ton of parts, very tight heat exchangers that get plugged up, large 200,000btu gasvalve burner, a bunch of highlimit, flow switches, water temp sensors that are all prone to failure. You might be one of the lucky ones who buy one and dont have issues with it but if your not i promise you will regret it.
Another issue is make sure you size them for your biggest demand, for instance they size them based on fixtures ( 4 fixtures, 8 fixtures) if you ever plan on running a dishwasher, doing laundry, and having a shower at the same time plan on buying a 200,000 plus btu unit, we ussually install 400,000 btu units for a household of 4 people or more.
I dont wanna seem like there all crap but coming from a service technician where we warranty the product for the first year its a real pita, i absolutely hate working on them, then after the first year i have to listen to customer complaints on how much they cost to maintenance and repair if they break down, we always try and talk people out of buying them now unless space is a factor.