Solar Panels in the Roaring Twenties: A Day & Night Solar Heater Company Pamphlet, ca. 1921

by Paul R. Spitzzeri

Photos of the Workman House and La Casa Nueva from the 1920s show, on the south-facing portions of the roofs of both structures, solar panels.  Here we are nearly a century later and, while solar panels are increasingly being used for electric power generation, it is little known that panels were used to heat water in residential and commercial buildings on a fairly large scale locally.

This was because William J. Bailey of Monrovia came up with first commercially-viable solar heating system for water through his Day & Night Solar Heater Company.  Bailey’s patent for his innovative system was registered in 1910 and he set to work developing and selling his product.  Prior to his developments, solar heating meant having the sun’s rays strike a tank painted black, though the loss of heat at night was striking and counter-productive.


Working from a Monrovia factory with a main sales office in downtown Los Angeles and branches at Ontario, San Diego, Oxnard, Visalia and Fresno, the Day and Night Solar Heater Company claimed, by the early 1920s, to have installed over 4,000 solar heaters in houses, hotels and public facilities throughout greater Los Angeles.

Tonight’s highlighted artifact is a pamphlet from the company, with a date stamp, perhaps from a library, of 22 August 1921.  It was around this time that the Workman House, acquired by Walter P. Temple not quite four years prior, underwent a significant remodeling.  Part of that work included the introduction of indoor plumbing with a first-floor bathroom installed in the center of the adobe portion of the historic house.  On the south-facing portion of the main two-gabled roof was a “sun coil” system to heat water for the bathroom.


A few years later, when La Casa Nueva was built, the same system was installed on the south-facing tile roof of the two-story structure and the sun coil was used to heat water for the two second story bathrooms.  Though we lack documentation about where these systems were purchased, it seems almost certain that they were from Day & Night.

The pamphlet promised that owners of the system could “cut down your hot water household expense by a full three-fourths, or more.”  It boasted that “ten years of successful manufacture are behind” the company’s product, as well as improvements over that decade.  Acknowledging that there were other solar heaters available, it advised, of course, that readers not “confuse those with DAY AND NIGHT” because “that will be doing an injustice to it and to yourself.”


The company pledged that “either it does the work, or out it comes—without expense to you,” but added “we do not have to remove these DAY AND NIGHT Solar Heaters” because of their reliability.  This included the fact that most of the year in greater Los Angeles offered abundant sunshine, while, even in winter months, there would only “be a few days . . . when your hot water supply will be ‘lukewarm’ or little better,”  Then, a gas, electric or other system would “help old DAY AND NIGHT out.”  It was suggested that an auxiliary system be connected as a backup and a “Bailey Booster” was offered as “an inexpensive gas heating arrangement.”

On the inner portion of the pamphlet were illustrations and text about the inner workings of the system.  A four-inch thick “practically air-tight” box was covered with glass beneath which was a coil of copper pipe sitting atop a sheet of copper.  When the sun’s rays hit the glass, with the copper adding to the process, the water absorbed the heat as it moved into a storage boiler.  In a recirculating process, cold water from the boiler then entered the sun coil, while “the water that was heated first will return to the Sun Coil, and be heated to a still higher temperature.”


Retention of heat in the boiler, which “is encased in a packing of great heat-retaining properties,” was effected by placing it in an insulated container.  In some cases, this looked like a chimney on the roof, so that galvanized iron sheeting was at the cap, while plaster or roofing material covered the outside.  For La Casa Nueva, a pair of redwood tanks, one over each bathroom, were placed in the attic to store the water.  It was promised that “the loss of hear by radiation will not exceed one degree per hour” even for the smallest boilers offered.

Moreover, these boilers carried no risk of explosion or fire and, of course, no need for a match for a pilot light.  Little maintenance was said to be required, just occasional washing of the glass on the sun coil to keep it free of dust and a flushing of the boiler once a year to remove any “foreign substance.”  A pressure regulator would keep the system in balance.


The firm offered a one-year guarantee against workmanship defects or with materials, with repairs done free during that period.  It was added that, while roof systems were common, they were also situated on the ground, on an outbuilding, and “on pergolas, as awnings over windows or cellar-ways—and otherwise, as conditions permit.”

Eleven photos on the fully folded-out pamphlet showed a variety of ways in which systems were installed.  Moreover, they included houses, a hotel on Catalina Island, a plant at the Army Balloon School at Arcadia (opened during the First World War), and at a plant at Exposition Park in Los Angeles.  A panoramic photo at the top showed sixteen systems in one Monrovia neighborhood and it was pointed out that the foothill city had “more per capita than in any other city in the world.”


At a centennial commemoration in 2010, historian John Perlin observed that the registering of Bailey’s patent in 1910 “was the hour of birth of the modern solar thermal water heaters.”  Day and Night sold its product in California, Arizona and Hawaii, but a problem emerged very quickly in the form of competition.  Natural gas became a significant source of energy during the Twenties and ate away at the market share of the company.

A 1979 Washington Post article titled “A Solar Energy Heyday” reported that, by 1920, there were more than 1,000 systems installed by Day and Night, though, again, the pamphlet, within a year of that, claimed four times that number.  With the acceleration of the use of natural gas, however, only 350 units were installed in 1926, according to the Post.  Four years later, as the Great Depression heated up (!), only 40 units were sold by the company.

Workman House South Elevation ca 1920s

Meanwhile, though, Bailey sold his rights with Miami’s Solar Water Heater Company buying them in 1923.  In almost perpetually sunny southern Florida, the solar water heater business skyrocketed and, prior to World War II, the paper observed, 100,000 units were installed.  Low-interest government loans and requirements for their use in government-owned housing helped foster the industry.  Wartime rationing of materials curtailed growth.

After the war, cheap electricity, higher material prices for solar systems, and older systems were replaced by newer water heaters powered by electricity and gas.  Yet, the article concluded, and remember this was almost 40 years ago:

The sun provided a portion of America’s energy needs for almost 50 years.  No pollution, radioactivity or raped landscapes remain as a legacy. The water heaters functioned quietly, cleanly and efficiently when no alternatives were available.  This suggests that the sun can have a renaissance, using technologies that are little different from those developed in the early 20th century.

Today, the technologies have changed and vastly improved and solar energy is used in greater degrees year after year, especially in the Sun Belt, Hawaii and other sun-soaked regions.  Climate change, not in the public discourse aside from a very few early prognosticators, is a major part of the motivation to develop cleaner forms of energy.

Courtyard Of La Casa Nueva

To know that, a century ago or so, solar panels were used to heat water might come as a great surprise to those reading this post.  For a brief time, until the rise of natural gas and other factors, for the most part, diminished the demand, these systems were viable and in use locally and elsewhere.

The Temple family saw their value and invested in the solar water heating system, almost certainly Day and Night products, for the Workman House and La Casa Nueva and were at the vanguard of an emerging technology foreshadowing the future.  This pamphlet, along with photos of the houses and the panels, helps illustrate that story.

4 thoughts

  1. Fascinating information that needs dissemination in our current times. The development of natural gas from the oil fields of California was the death knell for solar water heating but there was also another issue lurking that might not have been apparent in the 1920s but is the likely reason that the panels were removed from the two historic houses in the 1940s. Remember that the commercial occupants of the houses would have wanted to decrease their water heating costs and if the 1920s panels had continued working efficiently, they most likely would have retained them and they would still be there today.

    The Day and Night design directly heated the water that was to be consumed. This is the most basic design and theoretically (with no moving parts) it should be still working today except for the fact that the water in the Los Angeles area is ‘hard water’. Meaning that it has a very high level of dissolved minerals and salts. Those crusty white deposits that collect on your shower heads and faucets. These deposits also collect in the pipes of the solar system and plug up the circulation. (the circulation was thermal circulation – no pumps moved the hot water) As the effective size of the pipe is reduced and less water circulates through the system it operates less efficiently and the home owner runs out of hot water sooner. The home owner may not notice the drop in solar output but as the auxiliary heater has to kick in more often to make up the additional temperature, the bill for the water heating goes up. This corroding and plugging of the heating pipes can occur in about 5-10 years. (perhaps the reason the systems were removed in the 1940s?)

    Today the best system design uses a heat transfer liquid (like automobile antifreeze) to circulate in the heat capturing solar panels and then flows through coils in a transfer tank. (like a typical hot water heater but highly insulated) The coils are submerged within the water that you want heated. The domestic water and the heat capture liquid do not mix. This design keeps all the domestic hot water away from the cool night time air (where it would lose a lot of heat each evening) The extreme heating and cooling happens to a liquid that does not contain minerals and therefore does not plug the circulation pipes.

    The heat transfer tank is a tank just like a gas water heater and any mineral sludge can collect at the bottom and only needs to be flushed out regularly, but it is not as susceptible to plugging up.

    A side note to solar heated water. The biggest challenge to a system is the time of day that bathing occurs. If you take your shower in the evening, no problem, the water has been heating all day. If you like your shower first thing ins the morning it might be difficult for the system to provide all the necessary hot water after being exposed to cold night time temps for the previous 12 hours. The Day & Night system met this challenge with their large well insulated storage tank that would hopefully store enough hot water to meet the needs of a family in the morning.

    As an FYI the White House had solar panels installed during the energy crisis of the 1970s They were removed about 10 years later. . . . Good idea, but the system does not last forever.

  2. Thanks, Jim–interesting about the effects on hard water and pipes regarding the Day & Night system, but also about modern methods for delivering the water without plugging the pipes!

  3. Jimmy Carter had solar hot water panels installed on the White House in 1979.
    Ronald Regan had them taken off in 1986, supposedly to allow for re-roofing the place. They were not put back on.
    It is true what a previous commenter wrote about mineral deposits in the tubes of solar thermal collectors. Now that our industries have mastered Silicon, many of us have found that photovoltaic panels are a cheaper way to heat water than solar thermal. And photovoltaic panels have no moving parts. They do require more square meters of sunshine though. The balance of the PV–>DHW system is a control box and a commodity electric water heater, commonly set up with a grid-connected heating element in the top of the tank for extended cloudy weather. The only maintenance required is the same as your present water heater, which is to occasionally drain sediment from the tank.

  4. Hi Pete, thanks for the comment and it is certainly interesting placing the solar panels used at La Casa Nueva and the Workman House in the context of the development and history of the product over a century!

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