- Hot Water Requirements: Your hot water requirements are directly proportional to the number of people in the cottage at the same time and your normal usage of water. For instance, do you wish to have two people showering at the same time (in different showers....), or will you have a dishwasher, and other appliances that need hot water. Generally speaking a shower need about 3 to 4 gallons per minute of hot water. So for two showers your water heater needs to supply about 7 gallons per minute. The more capacity needed the more expensive.
- Single Application versus Whole House: Do you only need to supply hot water to a single appliance, or do you have two or more locations (kitchen, bathroom, laundry room, etc...) that need hot water. There are single application tankless water heaters that would fit in a cabinet in a bathroom that can be dedicated to providing hot water to the shower only. But for most needs a whole house water heater is the ticket - that would be installed in the basement.
- Heat Source (Electric versus Gas): Electric is a bit more convenient as it required no venting, however, it requires a high AMP circuit, often 120 AMPs, and even the largest of residential systems can not provide enough water for one application. Furthermore, it is recommended that they be install close tot he electrical panel. Gas while more complex just simply provide more hot water and are a bit cheaper to run.
- Heat Source (Natural Gas versus Propane): At the cottage it is like you will have no access to natural gas so the choice will be propane. Just be sure to order the LP or propane version - the natural gas model won't work properly with propane.
- Venting Type - Open combustion installation (SINGLE PIPE SYSTEM) versus Room sealed installation (TWIN PIPE SYSTEM): In an open combustion installation only the exhaust vent is installed to the outside - the system pulls in air from the room the heater is installed. For smaller systems this may not be a problem but for larger systems - like the 2400ES that we are using - it requires a room the size of entire single floor - which we don't have. PLUS you can't use the single pipe system in a region which has cold climate - which we do. Twin pipe systems usually come with a direct air vent system that uses an internal fan to pull in and push out the air. Quite frankly I feel safer with the direct vent two pipe system!
- Venting Location (Vertical versus Horizontal): The exhaust and air intake can either be routed vertically through the roof or horizontally through an adjacent wall. Which you do depends on a number of factors but the key ones are: location of the heater, the acceptability of the exit point per building code. We used a vertical vent for the exhaust and a horizontal for the intake because 1) you can not vent under a deck - and our deck goes almost completely around the cottage, 2) we wished to place the unit centrally to serve all locations equally, 3) the one wall that was available we did not wish to place the heater there
The are a six key considerations when selecting the right size and type of tankless water heater: