Sizing Your Tankless Water Heater
Before you purchase a tankless water heater it is important to have a good understanding of your hot water needs. Mostly this boils down to your shower-tanking habits. Showers are typically the largest hot water requirement in a home. Showers last perhaps 20 minutes and a typical shower head is 2.5 gallons per minute (GPM). Many families use cold water when washing their clothes and many dishwashers have their own pre-heater built in.
To get an accurate picture of your own shower habits you need a timer, a bucket and a thermometer. First measure the temperature of a glass of cold water straight out of your tap. This is your base temperature. Then measure the temperature of the hot water coming out of your shower head. This is your target temperature. Subtract the first from the second and this is your required temperature rise.
Now take a bucket of known volume (1 gallon bucket, for example) and time how long it takes to fill the bucket straight out of your shower head. With this number we can easily determine your shower head's flow in GPM.
Now you need to determine how many showers your family may take at the same time. Some families tell us that although they have two showers, they are used to only taking one shower at a time. This is fine, but just consider that when you sell your home the next family may desire to use both showers simultaneously. Add the GPM of all the showers that my run at once.
With your maximum flow rate (of showers) and your desired temperature rise we can then help you find the best tankless water heater for your needs. The Bosch 2400E, for example, can produce 6.35 GPM at a 45 degree F rise. This is plenty for two showers at once.
Our other gas tankless water heaters, such as the Bosch 1600H (Hydro Ignition), the 1600P (Pilot Light), and the Bosch 125FX (Electronic Ignition) all produce 4.25 GPM at this same 45 degree F temperature rise. They are all suitable for running one shower at a time.
Natural Gas, Propane or Electric?
Many of our customers have already decided between Natural Gas, Propane or Electric solutions before they even call us. For those of you who have not yet decided which way to go, we typically suggest gas solutions over electric solutions.
The electric whole house tankless water heaters require a high Amperage when in use. This means that they consume large amounts of electricity when heating the water.
We recommend that all of our customers understand the Amperage requirements and consult with their electrician before purchasing an electric tankless water heater.
The main considerations for installing a gas tankless water heater (Natural Gas or Liquid Propane) are the Gas Line Sizing requirements and Venting requirements. Please review the Installation Manual for the heaters you are considering. All of the Installation Manuals are available for download directly from our web site.
Indoor or Outdoor Models?
Most of the gas tankless water heaters and all of the electric tankless water heaters we carry are designed to be installed indoors. Indoor gas water heaters MUST be vented. This venting adds to both the material cost and the installation cost.
Our Outdoor gas tankless water heaters (Natural Gas and Liquid Propane) are designed to be installed outside and require no venting. In addition to the material and installation cost savings, you will also save more indoor space when going with an Outdoor solution.
Outdoor tankless water heaters are designed to be installed only in areas that do not experience freezing conditions. Our Bosch Outdoor heaters are designed with freeze protection down to 5 degrees F above zero. These heaters are designed to withstand an occasional night freeze; they are not designed to protect against prolonged temperatures below 32 degrees F.
Bosch will not warrant heaters that crack due to freezing conditions. Bosch recommends installing Outdoor Tankless Water Heaters only the following states: Florida, Georgia, North Carolina, South Carolina, Alabama, Mississippi, Arkansas, Texas, Virginia (only in zip codes beginning with the first three digits 850-857 and 864), Arizona (in zip codes beginning with the first three digits 850-857 and 864), Oregon (in zip codes beginning with the first three digits 970-975), Washington (in zip codes beginning with the first three digits 980-986), California (except in zip codes beginning with the first three digits 935 or 961).
Bosch Product Selection Guide
Bosch provides a Product Selection Guide that summarizes all of the Bosch tankless water heating offerings.
In this guide you will find information on each heater's dimensions, weight, average efficiency and warranty.
Additionaly, for gas heaters you will find the BTU Input, Energy Factor, ignition method, flue size, and minimum water flow required. For electric water heaters you will find the wire size, voltage, amperage and kilowatts.
