How Do Solar-Powered Water Heaters Work

Solar-powered water heaters are a popular way to heat your water for your home and business. These solar-powered water heaters are not a new invention. In fact, the world’s first commercial solar water heater was patented in 1891

Today, solar-powered water heaters are a cost-effective alternative to conventional water heaters. They’re also very environmentally friendly.

Are you thinking about switching to solar power? What are the benefits of solar-powered water heaters and how do they work?

Components Of A Solar Heater

To understand how a solar-powered water heater works, it’s important to know the basic components. These include:

Main Components

  1. Solar Collector: Also known as a thermal panel, solar collectors are usually installed on the roof. Water or heat transfer fluid flows into the collector and gets heated by the sun. Then the water flows into the tank and other system components. Solar collectors for residential homes come in three different varieties:
  • Batch Collectors
  • Flat-plate collectors
  • Evacuated tube collectors
  1. A Tank: This is where your hot water will be stored after the heater works its magic.
  2. A circulating pump: This will carry the heat transfer fluid or water throughout the system.


A thermal regulator may also be included. This indicates when the water in the collector is hotter than the water in the tank.

How Do Solar Water Heaters Work?

A solar-powered water heater system generally starts with a collector installed on the roof. This absorbs light rays and converts it into heat. When the thermal regulator detects that the collector is warmer than the water in the storage tank, the heat gets transferred to a water tank. This transfer occurs either by pump or inherent water pressure. 

Types of Systems

There are several types of solar-powered water heaters. This is because there are many types of climate regions and different types of solar-powered water heater systems that work well in them.

Active Solar Water Heating Systems:

When it comes to active solar water heating systems, there are two main types: direct and indirect circulation. The main difference between direct and indirect circulation is the use of heat-transfer fluid to warm the water.

Direct Circulation Solar Water Heating Systems

Direct circulation pumps water into the solar collectors and then through the home. Experts recommend these for warm environments that don’t experience snow or ice during the winter because a frozen collector could damage the system. This makes direct circulation systems perfect for our beautiful island of Oahu.

Indirect Circulation Solar Water Heating Systems

Indirect circulation systems pass a heat transfer fluid through the collectors and into the heat exchanger. The warm water is then transferred to the home’s water heater. The heat transfer fluid is non-freezing. This means indirect circulation systems are great for climates with freezing temperatures.

Passive Solar Systems

Passive systems use natural convection to circulate heat transfer fluid or water, without any pumps. Most water is sourced from the municipal water system or well water. Both of these have inherent pressure that pushes the water to the roof system and back down to the water tank. When the water reaches the tank on the roof, it gets heated in the collector tubes throughout the day. Then, the water is transferred back down into the home’s main water heater or to the water fixture directly in some cases. These usually cost less than other solar-powered water heaters but they aren’t as efficient.

Other System Considerations

The type of storage tanks and collectors can influence how your solar-powered water heater works.

Why Use A Solar-Powered Water Heater Over A Traditional System?

Solar-powered water heaters and traditional water heaters both heat your water, a necessary function in any home. Solar-powered water heaters won’t decrease your water usage, solar offers many other benefits, some including:


Most water heaters use natural gas or fossil fuels to heat water. Switching to a solar-powered water heater decreases your use of fossil fuels and natural gas. This directly reduces your carbon footprint and can improve air quality.

Lower Utility Bills

Instead of using municipal electricity to heat your water, a solar-powered water heater can handle most of your water-heating needs. This will directly lower your utility bills and can pay for the cost of the system in a few years.

Higher Home Value

In 2019, findings by Zillow that showed solar-powered homes in certain states can increase the value of a home. In Hawaii, solar-powered homes can increase the value by 4% or up to $24,526 for a medium-sized home.

Other Types Of Deductions

In Oahu, you can receive $1,250 as a Hawaii Energy Rebate toward installation costs of your solar-powered water heater system.

535 Plumbing

Are you interested in installing a solar-powered hot water heater? Contact us at 535 Plumbing! We are a Hawaii Energy Participating Contractor and can help you every step of the way. We will conduct an analysis of your hot water usage, calculate projected savings, estimate your costs, help with securing the Hawaii Energy Rebate, and we’ll inspect the system for quality assurance. Call us today to make an appointment at (808) 300-0535!