What is a passive solar hot water system?

Nowadays, making a shift to renewable energy resources is what everyone is talking about. You can play your part in environmental protection by going solar and reducing the use of fossil fuels. Getting a solar water heating system is the ideal choice for many reasons.


This article goes over why solar water heating systems are the future. Solar water heaters are a long-term investment in renewability, as they are cost-effective, easy to maintain, and last a lifetime.

Installing solar panel in the roof

With the installation of solar water heating systems, you can lower your hot water bills drastically and also help in reducing pollution. Traditionally, most of us have electrical or gas heaters installed, that are dependent on burning fossil fuels that turn into harmful greenhouse gases. These gases have an extremely negative impact on the climate. 


There are two main types of solar hot water systems: active and passive. We discuss the most efficient and effective option, the passive solar water heating system and its different types in depth.

Passive solar water heaters, also known as the domestic passive solar hot water heating systems, utilize the sun’s energy to heat the water in the tank. Passive solar water heating systems do not require any additional energy resources to heat the water that passes through the collector’s tube.


The Smart Investment

Initially, investing in a passive solar hot water system might seem like a costly option, but with such easy-to-install systems and very little maintenance, this is the smartest decision. Solar water heating systems last up to twenty-five years or even longer with proper maintenance.

Types of Passive Solar Water Heater Systems

There are many types of passive solar water heater systems, and each has its benefits and limitations.


Glazes Flat Plate Collectors

These systems are designed within a metal box, which is insulated and weatherproof. The box contains a dark absorber plate under one or more glass or plastic covers. When the sunlight hits the absorber plate, water-filled heating tubes activate, and the water is circulated through to the tank. 


Unglazed Flat Plate Collectors

Unglazed flat-plate collectors are similar to Glazed collectors; the only difference is that they don’t heat the water as much as Glazed collectors do. These systems are generally used for swimming pools or car washes due to their lower heating capability.


Evacuated Tube Collectors

Evacuated tube heating systems consist of insulated tubes made from glass. These tubes form a vacuum space that prevents heat loss. When the sun hits the inner tube containing the water, it provides heat via thermal power. This system provides better efficiency and reaches high temperatures ranging from 77 °C to 177 °C. 


Batch Solar Heaters

Batch Solar heaters are also known as Integral Collector Storage Systems. These systems consist of one or more water tanks that allow sunlight to pass through. The water absorbs the heat from the sun and rises in temperature. It is the cheapest heating system as it doesn’t require any additional accessories, other than the tanks. 


However, it solely depends on the temperature of your residence too. For instance, during winter, it might not be as efficient as it might become too cold for the system to heat the water properly.

Solar Panel Energy Process
DHW Tank

Passive Solar Water Heating System – Advantages  

Passive solar hot water systems do not require any additional energy resources to run other than the sun. This means that they don’t require expensive fuels to work and that lowers the attached installation costs. But the benefits don’t end here; let's look at some of the benefits of these systems.

Solar Consumer Benefits

  1. Environment-friendly: In a society, understanding your role in the protection of the environment and reducing pollution is essential. For people who are considering shifting to passive solar hot water systems, the primary attractions are that they are environmentally friendly.
  2. Year-round Hot Water: Being free of expensive heating makes solar passive water heaters an appealing option for installation in different terrains and environments. In areas that suffer from electricity outages, solar heaters can keep the hot water system going, unlike conventional electric heaters.
  3. Cost-Effective: A great benefit of solar is a significant decrease in the ever-rising fuel costs around the world since this is one of the best eco-friendly options. 
  4. Little to no Maintenance: These systems can reduce your electricity bills to a minimum with no electrical and mechanical features involved. In addition, with passive solar hot water systems, the need for regular maintenance or replacement is highly unlikely.
  5. Easy Installation: With the ability to install these systems easily as a replacement for your current water heater system, you don’t have to take out and reinstall everything. With multiple tax incentives and installing incentives by Federal and State laws, you can end up saving a lot of money immediately after the initial investment. These saved costs can help repay the investment in a few short years, and you can enjoy the benefits for decades to come.

Solar Contractor Benefits

For contractors, Passive solar heater systems open a more dynamic relationship with your valuable customers. Since these systems are off the grid and don’t involve complications, it is easier for the consumer to understand the initial cost in favour of the long-term reliability of the system.

Passive solar water heating systems don’t involve a lot of proprietary equipment, you can order, and stock up on the components which help you save high management costs and warehouse space.

All these cost savings will help you increase your spending for the growth of your business along with the incentives that might be provided by Local and Federal laws. You can enjoy the benefits and pass them on to the consumer as well.

DHW AE Collectors

The Difference between Active and Passive Solar Water Heaters

To understand which solar water heating system is better amongst the two, we have discussed both, active and passive water heaters and how they work. Being used liberally, the more efficient and proactive one is the passive solar hot water system; keep reading to find out why.


Active Solar Water Heaters

Active solar water heaters are a little more complicated than passive ones. These heaters use pumps to move the fluid through collectors, where the temperature increase takes place.


There are two basic types of systems; both of these rely on water circulation, the only difference being the direct or indirect usage of collectors and storage tanks.


  1. Direct circulation systems move the domestic water through the collectors and storage tanks so they are suitable for deployment in moderate climates where the extreme temperature is not a concern.
  2. Indirect systems are used for climates where water might freeze in the collectors. Hence, a non-freezing heat transfer fluid is used to transfer the heat to the water in the storage tanks.
Solar Panel Connection

Passive Solar Water Heaters

Passive solar water heaters are usually a less expensive option since such systems avoid the added costs of an active solar water heater system. These heating systems don’t require a pump to power them; rather they rely on basic water convection.


The system depends on gravity and an integral storage system or thermosyphon system. Unlike active water heater systems, passive systems don’t use pumps, thermostats, sensors, or other mechanical parts which in the short-term means saving costs of powering these systems and in the long term means that maintenance is kept to a minimum. These systems are quite inexpensive to install and maintain.

Do You Want Special Offers?


Investing in a passive solar hot water system can be a big deal for you. Choosing the right solar contractor and getting the most out of your investment, we suggest you contact Everything Solar for all your heating requirements.


Book a consultation now!

Frequently Asked Questions about Passive Solar Hot Water Systems


What Is Passive Solar Water Heating System?

A passive solar water heating system uses the heat directly from the sun to provide warm water for your house. This is a very cost-effective heating solution as it does not require any other energy source because it solely relies on gravity and convection.


What Is The Difference Between An Active And Passive Solar Hot Water Heating System?

Solar water heaters are a renewable form of heating system used today. They are either passive or active; both have their benefits and drawbacks. Passive solar heaters are more direct as they use the heat from the sun to heat the water whereas active solar water heating systems require additional equipment such as pumps, sensors, controllers, etc.


How Does A Passive Solar Water Heater Work?

A passive solar water heater is an old-school method that has been reimagined by today’s engineers to ensure effective heating. In this system, the water that needs to be heated passes through the collectors that take heat directly from the sun. The concept of how hot air rises is implemented with this system so the hot air is collected into the water tank.


Is A Solar Water Heater Passive Or Active?

A solar water heater can be both active and passive. However, passive heating systems are much easier on the pocket because they do not require any additional energy source. Passive solar water heating systems can either be ICS systems or thermosyphon.