How to Build a Passive Solar Water Heater

Learn how to build a passive solar water heater. A solar heater can be simple to construct and reduce your utility bills. We’ll explore the various types of solar water heaters, and learn to build an easy and affordable model.

| October/November 2007

Home with hot water heater

Building a solar hot water heater is simple and can produce significant savings on utility bills with minimal investment.

Illustration by Dave Channon

Follow these guidelines to build an easy and affordable solar hot water heater. Explore the various types of solar water heaters. Learn how a passive solar water heater can be simple to construct and reduce your utility bills.

How to Build a Passive Solar Water Heater

For the do-it-yourselfer seeking an inexpensive, easy-to-build solar water-heating system, the integral passive solar water heater (IPSWH, pronounced ips-wah) is a dream come true. All you need to build this down-to-earth water warmer is a discarded electric water heater tank, a homemade insulated plywood box to house the tank, a sheet or two of used window glass or clear plastic, a few common plumbing fittings, some pipe and a bit of insulation. Add a few satisfying hours of measuring, thinking, sawing, hammering, painting and wrench-turning, and you’ll have a continuous supply of hot water, provided virtually free of cost by that friendly furnace in the sky (the only safe nuclear reactor, 93 million miles away).

First, let’s review the basics of solar heating for new recruits to the wonderful world of renewable energy. There are two basic types of solar water heaters, active and passive. Active systems depend on external power to run pumps to circulate the heat they gather; passive setups don’t. Passive systems may be less efficient at any given moment, but they are much more dependable and cost less per unit of heat captured. Integral passive solar water heaters, also called batch heaters, are the simplest of the passive systems, and their reliability and independence from external power lead to long-term production at a very low cost. I know of a system in Davis, Calif., that has operated for 30 years at a cost per kilowatt-hour equivalent of about a penny.

Batch heaters have long been known as the best choice in warm climates or for seasonal use in colder areas, and recent work with improved materials and designs suggests they may also be the best choice even in colder areas. For owner-built applications, they outshine their flat-plate and evacuated-tube competition in almost every way, including reliability and ease of installation. They have excellent potential for retrofits and are ideal for a range of farming and commercial applications, providing low-cost hot or warm water for washing or preheating for higher temperature uses.

Solar Water Heaters: Five Hot Ones

Now that you know the basics, let’s take a look at five of the many types of batch heaters in use today.

The Solar Shower is really a small-scale batch heater, a classic design using clear and black plastic to make a portable and surprisingly effective solar water heater. Water is placed in the bag and then set out with the clear side facing the sun. Within an hour, the water starts to heat up, providing a delightful shower on even a cool day if the sun is bright. I have used these for years while camping and am always impressed with how well they work.

7/4/2017 9:12:32 PM

the article says how to build. there is nothing in the article that describes how to build a solar water heater. It talks about various parts etc. but no concrete plans. Why not describe with pictures how this writer did this. It would be so much more helpful

3/18/2016 2:47:31 AM

Thanks for sharing this blog,its really informative one,now a days solar has been used by every houses,due to power consumption.​

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judy murphy
2/1/2014 12:11:18 PM

How can I make a Solar Water Heating system for my above ground Pool?

6/16/2013 4:48:50 PM

In New Mexico, they recently passed a law that mandates that all solar systems, (HW, Solar Photovoltac, Thermalvoltaiac, etc) must now have a permit to hook up to the house.


Its fustrating that just when you think there is a way to deal with this with no cost, government comes in with a hand out.


5/29/2013 10:50:32 AM

Well, everybody knows whether one puts anything under the sun, it begins getting blazing gradually regardless of the surrounding temperature. It could be frigid icy or greatly sweltering, the free energy of the sun goes squandered unless it is tapped and saved. There are numerous diverse courses to tap the sun based energy for warming principally for residential used the precise first stage to bridle the free energy. The standard sun powered boards normal house hold things of the urban regions are dreadfully entangled assuming that one begins expanding his own particular.

james murray
12/8/2012 2:03:06 AM

question: since my residential water supply has a back flow restrictor on the line, in the event of excess heat and thus expansion could this set up potentially cause a system failure or ruptured line due to hydrostatic expansion with overpressure that has no relief ?

dan gretsch
8/17/2009 4:27:24 PM

Passive solar water heaters are great and have been used extensively around the world for low cost water heating. When a location has tougher standards for reliablity and performance the % of passive water heaters installed drops off tremendously. These systems are particularly good if you want to make them yourself but if you want an aesthetically pleasing, high performing, reliable appliance I would probably focus on active systems in the U.S..

b knight
5/1/2009 9:18:06 PM

Here's a link to a page with some pictures of a breadbox and batch solar water heaters. The second unit, without the "box" and no insulation is used as our cottage to preheat water for an outside shower. Simple designs and they work well.

4/21/2009 11:51:56 AM

is it possible to use an Acoil from an old ac unit in the furnace ducting to use the hot water to space heat a house to stop using so much fuel oil during the heating season?

michael sakowski
7/4/2008 7:32:59 AM

I just built a 20-gallon solar heated shower that works great! It only cost me about $25 :) since I was able to recycle a lot of scrap items like old boards or pieces of plywood and an old busted garden hose. I put the plans online at Take a look!

10/19/2007 8:51:25 AM

Please, I'm a student of Kwame Nkrumahh University of Science and Techology-GHANA. My project is to design and construct a solar water heater for a six member household. Please, I need your assistance throughout my project right away.

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