Compact Water Heating for Tiny Houses

Although a bit more expensive, a “triple threat” system of solar, electric and gas backup delivers under every scenario.

One of the simplest, lowest-tech systems we’ve seen for water heating on small homes is essentially a black tube mounted on the roof, that’s heated by the sun, and gravity feeds hot water to your shower or sink. In southern climates, there are many variations on this concept, and at least one commercial product called Road Shower 2 (Fig. 1).

Any number of other solar hot water heaters are available of course, but most require a storage tank inside the structure—more space than you may want to give up. This is the same limitation that applies to an electric hot water heater. There are several compact units on the market now that do a great job in a relatively small space, using 110 volt electric.

For example, Rheem makes a six-gallon electric heater that’s well reviewed and retails for about $250 (Fig. 2).


Also, Bosch offers the Bosch Tronic 3000 T 7-Gallon Electric Mini-Tank Water Heater (not shown).

But if you want the flexibility to live off grid or take your home on the road, it doesn’t hurt to have a gas-fired backup. A budget approach would be to acquire one from an expired RV at a junkyard. You many also end up with a “hybrid” heater that does both electric and gas heating. Or you can purchase an inexpensive conversion kit ( that allows you to plug in your water heater when you have an electrical hookup (Fig. 3).

But one criticism of this electrical water-heating systems is that you’re wasting a lot of electricity to keep the water hot 24 hours a day, when you only need it occasionally. You have a couple of options. Put the plug on a timer, or install a smart switch you can control with your smartphone, and turn the water on and off at your whim.

If you use a lot of hot water, or plan to stay put most of the time, an on-demand propane gas water heater makes sense. This is a great technology, but for tiny homes, it’s really only suited for areas that don’t freeze, because you want to locate the unit outside your living space, as shown in this image of a Noritz on-demand unit posted on (Fig. 4).

Slow the Flow

Key to any efficient, low-volume water system is the use of an extremely efficient showerhead. Most showers operate at 2.5 gallons per minute, but you want a 1.5-gallon-per minute-head. Thus, with a six-gallon tank, you can still take about a six-minute shower (because you’re mixing hot with cold water). We’ve tested this model (, and it works flawlessly. You hardly notice the flow constriction (Fig. 5).

While you’re at it, go ahead and replace your kitchen and bath sink aerators with 0.5 gpm versions. We like the ones that allow you to switch between multiple flow rates in case you want to fill the sink quickly. The miserly setting is a silent governess for teenagers who like to run the water while they brush their teeth. 

This is Chapter 3 of the Tiny House Tactical Guide. Download this free Ebook here.