oh sure, hook us with the old cold shower question making us all think that this is a question related to human relationship problems 
Seriously, the tankless water heater sounds like a good idea and should work well for you. here is some info:
Tankless water heaters heat water directly without the use of a storage tank. Therefore, they avoid the standby heat losses associated with storage water heaters. When a hot water tap is turned on, cold water travels through a pipe into the unit. In an electric Tankless Water Heater an electric element heats the water. In a gas-fired Tankless Water Heater a gas burner heats the water. As a result, Tankless Water Heaters deliver a constant supply of hot water. You don't need to wait for a storage tank to fill up with enough hot water. Typically, Tankless Water Heaters provide hot water at a rate of 2 – 5 gallons (7.6 – 15.2 liters) per minute. Typically, gas-fired Tankless Water Heaters will produce higher flow rates than electric Tankless Water Heaters. Some smaller Tankless Water Heaters, however, cannot supply enough hot water for simultaneous, multiple uses in large households. For example, taking a shower and running the dishwasher at the same time can stretch a Tankless Water Heater to its limit. To overcome this problem, you can install a “whole house” type Tankless Water Heater or install two or more Tankless Water Heaters, connected in parallel for simultaneous demands of hot water. You can also install separate Tankless Water Heaters for appliances—such as a clothes washer or dishwater—that use a lot of hot water in your home.