Problem Solved: How to Select a Water Heater for a Tiny House

Posted by Chas Kerin on September 01, 2016
Problem Solved: How to Select a Water Heater for a Tiny House
Bosch tankless point-of-use water heater

When homeowners decide to downsize, many might question how many bedrooms they need, bathrooms they want and whether that second garage is really necessary. But when they decide to truly downsize and build a tiny house, contractors are left with far more complex decisions to make.

Living in tight quarters is nothing new. In fact, New Yorkers have been doing it successfully for years. Complications arise, however, when homebuilders attempt to design an ultra-compact single family home with simple amenities like hot water.

When you’re dealing with less than 500-square-feet of space, how do you generate hot water efficiently for common tasks like doing dishes, laundry and taking a shower? Welcome to one of the most common challenges for the tiny house movement.

Think about the traditional, tank-style water heater sitting in most Americans’ basements. That 30-to 50-gallon unit would take up an absurd amount of space in a tiny house, wasting energy by heating water even when you don’t need it. For the often eco-conscious owners in the booming tiny house market, there are far better options.

Installing tankless hot water systems for a tiny home makes sense, in that such homes have very tight spaces with typically one bathroom and small shower. The greatest advantage of tankless units is that they provide hot water on-demand, allowing them to be installed in much smaller spaces than tank-type water heaters.

They have a longer life expectancy and are less likely to leak than tanks, while providing significant energy savings and peace of mind with nearly endless hot water generated only when it’s needed.

Some logistical challenges include selecting equipment offering the most efficient use of space and where are you going to put the equipment. Also very important is providing sufficient electrical service.

Electric whole-house tankless water heaters such as Bosch Tronic US 17 (17kW) require 240V 80 Amp hard-wired electrical service at minimum, requiring that the home has at least 150 Amp service to operate all the appliances. This may be achieved when the home is on a permanent lot, but is impractical for mobile home applications. The upside is that these water heaters are nearly 100 percent efficient, so that virtually all the electric energy goes into heating water, and no outdoor venting is required.

Another option is installing an LP (propane)-fired tankless unit mounted outdoors. Bosch offers outdoor mounted gas-fired tankless water heaters with thermal efficiency up to 98 percent. Intake and exhaust are provided directly outdoors, so no separate flue is needed. These units must be used only in areas with moderate ambient temperatures, such as the southern U.S. 

Bosch Greentherm ENERGY STAR rated residential gas condensing tankless water heaters were selected for “Green Builder Media’s 2016 Readers’ Choice Award,” citing durability, efficiency and high quality. 


Chas Kerin works for Bosch Thermotechnology Corp., a leading source of high quality heating, cooling and hot water systems. 

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