Making a solar water heater for the home

Posted4/3/2021 7:00 AM

Q: We have a large family and use much hot water. I cannot afford to have a solar water heating system installed, but I would like to make some type of solar water heater myself. What do you suggest?

A: Heating your domestic hot water is an excellent application for solar energy. Unlike solar space heating, water heating is needed year-round. This provides a good payback, especially if you build it yourself and must only cover material costs.


Your first step is reducing the amount of hot water consumed. With a large family, much of the hot water usage is for showering. Unlike clothes or dishwashing where the amount of hot water used is set by the appliance, you can modify showering to save much hot water.

Although you may get complaints at first, install low-flow shower heads. Family members will quickly get used to flow patterns. Install a push-button trickle valve on the shower. This allows you to reduce the water flow while lathering without having to shut off and reset the water temperature.

The two basic types of solar water heating systems are active and passive. An active system uses pumps, collectors and plumbing to provide the most hot water and efficiency. It is possible to buy all the components to set up an active system yourself, but it would require a high skill level.

For most homeowners, including myself (a mechanical engineer), building a passive system is a more reasonable project. With this type of system, the solar hot water storage tank also functions as the solar collector.

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Building a batch solar system to preheat water can cut your water-heating costs noticeably. Your water heater still brings the water up to the temperature you desire. The batch system warms the incoming water so it takes less electricity or gas for your water heater to make it hot.

A breadbox type of batch solar system is the easiest and least expensive to build yourself. It is basically a metal tank inside of an insulated box with one or two clear sides. The sun shines in on the tank and warms the water.

A variation on this design uses a vertical box and tank tilted so it faces the sun more directly. This is more efficient because it receives the sun's rays more directly and the warmer water naturally flows upward to the top.

Special tanks are available for this, but if you are lucky, a plumber might have an old water heater that does not leak. Strip off the metal skin and insulation and paint it flat black. It already has the water fittings.


Include valves in the piping so it can be bypassed during very cold weather and to drain it. Place it as close to your house as possible and insulate the pipes heavily.

The following companies offer solar kits and components: Alternative Energy Store, (877) 878-4060,; Build It Solar,; Solar Components, (603) 668-8186,; and Solar Direct, (800) 333-9276,

Q: Someone told me to put crumpled newspapers in my freezer to help save electricity. Does this really help, and if so, why?

A: As silly as it sounds, it should help. For efficiency, it is best to keep the freezer reasonably full. This reduces the amount of cold air lost when the door is opened. On the other hand, packing it extremely full with food can block proper air circulation.

The crumpled newspapers take up space. With their very low heat capacity, it takes little electricity to cool them. When you need more freezer space for food and remove the newspaper, not much energy is lost.

• Write to James Dulley at 6906 Royalgreen Drive, Cincinnati, OH 45244 or visit

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