Chemical automation for swimming pools and spas has often been compared to the thermostat that controls your heating and cooling system which is somewhat accurate but falls short of the full story.
The comparison accurately depicts the savings that can be realized in chemicals used to treat the swimming pool or the energy savings in heating or cooling which can easily be 30% but there is much more. A chemical controller will also save on wear and tear on all the wetted surfaces by keeping the water balanced so it will not be corrosive or scale forming.
Water is often referred to as the universal solvent and under the right conditions will dissolve almost anything over time. In a swimming pool, this means etching plaster surfaces, corrosion of copper heat exchangers and other metals. Water that is out of balance will also cause calcium to precipitate out of solution and onto surfaces which can plate metal fixtures, deposit on the pool surface making it rough and even coat heating elements and heat exchangers making them less efficient at heat transfer, thus using more energy.
Swimming pool chemical automation controllers will continually keep the water balanced and properly sanitized which makes the pool and spa much more appealing. Think how many people turn away from facilities that have cloudy or dull water, or eye and lung irritation due to the high levels of chloramines that are produced when a pool or spa treated manually will produce when they experience a bather load. This costs money also.
Having been involved as a witness for a couple of lawsuits regarding swimming pool chemistry, the facilities with data recorders incorporated into the chemical automation system are good unbiased witnesses to the quality of the water and thus provide another layer of protection which ultimately saves money.
As you can see the comparison of a pool chemical automation controller to a thermostat does not do the chemical controller justice. There is much more money to be saved and gained with the use of a chemical controller than a thermostat yet there is not a facility in existence that would dream of not having a thermostat on the pool or spa heater let alone to control its heating and cooling systems. Just think of the millions of dollars that could be saved annually if all pools were utilizing chemical automation to keep their water balanced and properly sanitized.