Though they have been improved and updated over recent years, gas tankless hot water heaters are hardly new technology. They have been trusted for decades all over the world. The sheer number of people who use them is proof enough that they work. But that does not mean that new customers cannot be disappointed by these systems. So, what should we look for and what should we expect.
We should expect our tankless hot water heater to do what it claims. Most of us cannot test the efficiency claims (though we probably can trust the energy star marks or the official testing), but will all be able to test straight away if it does not live up to the heating claims made by the manufacturer.
So pick from the on demand water heaters that claim high efficiency - for gas this is 85% upwards. Then pick a unit that will meet your needs.
The capacity of tankless hot water heaters is expressed in gallons per minute. So long as the combined simultaneous demand is never exceeded then you will never run short of water. It is this calculation of how much water is needed by appliances that run at the same time that is important. If you choose a unit that can match this demand, you should be happy with the unit.
If you choose your propane or natural gas tankless water heater from a trusted manufacturer you should get a quality guarantee. Have it installed professionally and you should enjoy years of use from the unit - the life expectancy is around 15 years, though check with each manufacturer.