Most of us don't bother looking for a new water heater until its too late. Even fewer are aware that there other options besides the traditional storage tank water heater. Whether you're replacing an old hot water heater or installing one in a new house, it's important to look at some of the advantages of choosing the tankless option:
Type - there are two main types of tankless water heaters: electric and gas/propane water heaters. Choosing between them depends on how much you want to spend, whether you have access to gas/propane, how much electricity costs and where you live. Most people choose a gas water heater because the cost of gas is approximately one third that of electricity. Gas tankless systems also have wider applications because they produce hot water at higher flow rates. An electric tankless system is an appropriate choice only when gas is not an option and no space is available for a tank hot water heater. Electric or gas/propane heaters can be whole house or point of use.
Size or Capacity - Decide the model depending on what capacity or size you need during peak demand, the incoming water temperature, and the desired outgoing water temperature. Most units advertised as whole house tankless water heaters will provide 2 to 3 gallons per minute (gpm) of hot water at a 70°F temperature rise. Choose the model of water heater closest to your flow rate and temperature rise needs. Choose the capacity during peak demand based on the number of users, the number of showers or bathtubs, whether or not you have a dishwasher, and how many hot water devices you expect to have open at one time. Add up their flow rates and this determines your desired flow rate for the demand of water.
Cost Effectiveness - tankless water heaters are the most cost effective when used in high flow rate applications. Because there are so many variables involved in calculating cost effectiveness, it's a good idea to do your own analysis. Analysis of a hypothetical situation reveals that payback periods for tankless heaters are significantly longer in lower water use applications (68.8 gallons per day) than in high water use applications (250 gallons per day). In the example, tankless water heaters have paybacks ranging from approximately 5.5 to 11 years in low water-use applications compared to approximately 3 to 7.5 years in high water-use applications. It is interesting to note that the tankless heater with a standing pilot light becomes more cost effective than the electronic control unit with the same flow capacity under high flow conditions.
