Don't expect to save money and make sure you know all the drawbacks. See
http://www.consumerreports.org/cro/appliances/heating-cooling-and-air/water-heaters/tankless-water-heaters/overview/tankless-water-heaters-ov.htm
If you have very cold water during the winter you must pay attention to
maximum temperature rise if considering an electric tankless.
I opted to stay with a regular tank gas water heater. Most of my hot water
use is start and stop, so using a tankless water heater would be an
annoyance and more expensive to install and use.
Good advice above. I had a friend who recently yanked his out. Too
many problems with temperature consistency and had pressure
differential trouble between the unit and the city's pressure...