Quick Multi-unit Configuration: if you are planning on using more than one tankless water heater in a parallel configuration, look for models that are designed to be configured this way. It is possible to connect tankless hot water heaters that are not designed to be connected, but it is more challenging and more expensive.

Energy Star: If you purchase a tankless water heater that is Energy Star rated, you know you've purchased a heater that is one of the most efficient available. What's the advantage to you? More hot water is created for less energy expended. Lower heating bills. Environmentally friendly.

Space saving design: Tankless water heaters tend to be fairly compact. If space is an issue for you, make sure the unit you get is indeed a "low profile" unit and fits into the space you have allocated for it.

Electronic ignition of gas: Electronic ignition sparks the combustion process, and makes it unnecessary to have a pilot light.

Wireless remote controls enable water users to remotely control the temperature of the water that is coming out of their faucet.

Indoor/outdoor installation: Some tankless water heaters are capable of being installed either inside or outside your home. The units that are installed outside usually require no dedicated venting.