A Complete Guide to Solar Water Heaters

The use of solar water heaters is a cost-effective and environmentally friendly way to generate hot water for your household needs. Why? The heaters, also known as solar hot water systems or solar-powered water heaters, rely on the free energy from the sun.

Because they use the  sun as a source of energy, solar hot water systems come equipped to work in pretty much any climate.

According to the US Department of Energy, heating costs work up to a little less than half of the utility bill in an average household. This makes it the most expensive component of your bill. Solar hot water heater help reduce this expense by cutting down the grid power needed to generate large quantities of hot water.

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    How Are Solar Water Heaters Different From Traditional Systems?

    Traditional water heaters connect directly with your household grid energy. Solar-powered water heaters, on the other hand, draw power from solar energy collectors, which collect energy directly from the sun. Such a system reduces your dependence on the electrical grid. In doing so, it helps you save money and go green for the betterment of the environment.

    Solar water heaters are a stand-alone system that does not necessitate the installation of expensive solar panels. Panels create electricity for your home, while water heaters focus solely on generating hot water for your home needs. Solar-powered water heaters can be installed in conjunction with panels or on its own. The two systems are mutually exclusive.

    How Does a Solar Water Heater Work?

    A typical solar water heater comprises of two parts – a solar collector and a storage tank. Depending on whether they have circulating pumps, the systems are categorized as either active or passive.

    Active Solar Water Heaters

    There are two types of active solar-powered water heaters:

    1. Direct circulation systems
    2. Indirect circulation systems

    In the active direct circulation systems, pumps circulate water from the collectors and into the household. Such systems are particularly useful in areas that do not experience freezing climates.

    On the other hand, pumps in active indirect circulation systems circulate a no-freeze heat-transfer fluid through the solar collectors and a device known as a heat exchanger. The exchanger heats the water and carries it into the home. The systems work best in areas that experience freezing temperatures frequently.

    Passive Solar Water Heaters

    In general, passive solar water heating systems are less expensive compared to active systems. They are also known to last longer and are typically more reliable than their active counterparts. However, passive systems are also less efficient when compared to active systems.

    There are two different types of passive systems:

    1. Integral collector-storage (ICS) passive systems
    2. Thermosyphon systems.

    Integral collector-storage passive systems work efficiently in homes that need significant amounts of hot water during the day and evenings. The heaters are used in areas that rarely experience freezing temperatures. 

    Thermosyphon systems are more expensive and reliable compared to integrated collector-storage systems. This type of heaters requires professional installation as the collector needs to be installed at a spot below the storage tank. The design allows water to flow through when warm water rises to the top of the tank, and cold water sinks to the bottom. The water heaters are best installed by experts because the storage tanks are heavy, and the design of the roof has to be considered.

    Read More: Active vs. Passive Solar Water Heaters

    Solar Storage Tanks and Collectors

    Most solar water heating systems generate enough hot water to cover the needs of an entire household. However, on some days, the solar collection might not be as robust. In such situations, a backup energy storage system or source is recommended. Passive systems typically contain a tankless heater that serves as a backup for such days. The energy source runs on electricity or gas.

    A thoroughly insulated storage tank is an integral part of solar hot water systems. In designs that contain only one tank, the same tank serves as a solar storage unit and backup heater. 

    In two-tank systems, the water is heated and then transferred to the other tank, which works like a traditional water heater.

    When it comes to residential systems, there are three basic types of solar collectors. They are flat-plate collectors, integral-collector storage system, and evacuated-tube solar collectors.

    Solar water heater

    Flat-Plate Collectors

    Flat-plate collectors are the most common in the domestic sector. This type of collector consists of an insulated and weather-proof box with a dark absorber plate. The insulation is crucial since it helps prevent heat loss in the system. On the other hand, the absorber ensures there is maximum absorption of heat energy from the sun.  

    Integral-Collector Storage System (ICS)

    Also referred to as batch systems, ICS are insulated and glazed boxes that contain one or more tanks or tubes. The solar collector receives cold water and preheats it. The water is then transferred to typical backup water heating units that work as a dependable source of hot water. This type of collectors should be installed only in areas that experience mild freezing as pipes placed outside the home, and are therefore likely to freeze in severe weather conditions.

    Evacuated-Tube Solar Collectors

    Evacuated-tube solar collectors contain rows of transparent glass tubes that are placed parallel to each other. Each tube features an outer tube and absorber made of metal, and a fin coated with solar energy-absorbing material.

    Choosing a Solar Water Heater

    Considering that there are many different types of solar hot water systems, it is understandably difficult to choose one. So, how do you decide on the most suitable system?

    The first step is to start with your household’s needs and then work your way to the kind of system. Here are the points to guide you through the choosing process.

    • Choose a direct active system if you do not experience below-freezing temperatures.
    • Go for an indirect active system if you live in colder areas. The primary reason for this is that such water heaters are built to resist damage from severe weather conditions.
    • If you use more hot water during the day, opt for an integral passive system, as such a system consistently produces hot water in batches.
    • If you want a system that does double duty to heat your pool, an indirect circulating system with heating fluid is your best bet.
    • Since a thermosyphon system is installed on your roof, it is a good option for those who have more roof space than living area space.
    • Select your solar water heating system based on how much sunlight your household receives, the quantity of heated water you need in a day, and your budget.

    Read More: Will Solar Water Heaters Grow in Popularity?

    What are the Most Preferred Brands of Solar Water Heaters?

    Today, solar technology has become a mainstream presence, especially in residential appliance applications. Several companies specialize in designing and manufacturing solar-powered heaters in the market. Here are some of the popular brands:

    Sunbank Solar

    A producer of solar water heating system components like pumps, plates, collectors, and others.  


    Features a wide range of residential and commercial solar energy solutions, including Solar-powered heaters.

    Duda Diesel

    A manufacturer of residential and commercial solar water heaters and machinery that runs on biodiesel and alternative fuel sources.

    Before you select one option over the others, do your research by checking the appliance’s efficiency ratings awarded by the Solar Rating and Certification Corporation (SRCC). The third-party data aggregated by SRCC helps customers compare the efficiency of various brands and solar water heater models.

    Best Residential Solar Water Heater Systems

    Whether you want a small system that heats your bath water to perfection or a larger one that keeps your pool at just the right temperature for a swim, there is a solar-powered heater made just for you. Here are the best residential systems to choose from:

    Duda Solar 200L Active Split System

    This 53-gallon active indirect heater is SRCC-certified and is perfect for homeowners living in cold climates because it is winter-resistant. Duda’s certified heater makes you eligible for federal and state tax exemptions and credits, too. Split hot water system allows you to heat water in a location that sees plenty of sunlight, such as the roof. The storage tank can be placed close to where the water will finally be used.

    Reviews suggest that the Duda Solar 200L Active Split System heats the water quickly, even with just a few hours of sunlight. However, if you travel frequently, this system might not be the right one for you. The 8L expansion tank cannot regulate hot water for more than a few days without usage.

    The kit contains all necessary equipment and components, and include:

    • Two gallons of propylene glycol needed for the solar collector’s indirect circulation system
    • A solar water heater working station
    • Safety systems such as an air vent that automatically purges air from the system

    Sunbank 40 Gallon Solar Water Heating System

    The Sunbank Solar Water Heater is a 40-gallon passive thermosyphon type of system. It is easy to install, more comfortable to use, and it requires little to no maintenance. It is a starter kit that has no extra frills or worrisome moving parts. The heater is perfect for small homes located in mild temperature zones.

    Certified by the SRCC, this passive system is relatively inexpensive and cost-efficient. 

    Some reviewers suggest that a single system may not be enough to cover significant hot water requirements. Installing dual 40-gallon systems might, therefore, be a better idea.

    The Sunbank water heater is a pressurized system as it does not contain pumps. 

    Sunbank Solar 40 Gallon Solar Water Heater

    In proper working conditions, each of the 15 evacuated solar collector tubes can collect more than 92-96% of solar energy. It is, therefore, best suited for installation on roofs that receive a sufficient amount of sunlight.

    Northern Lights Group SWH-1 Solar Hot Water Heating Package

    More expensive than other solar water heating kits, the SWH-1 package is an all-in-one solution to your residential solar water heating needs. This 50-gallon system is of an active indirect type. It is known to be one of the most comprehensive kits in the market today.

    Every component is provided, along with setup and installation instructions so you can do it on your own. The kit includes products from several different brands. Contained within the package is a remote controller that allows you to heat two completely separate zones, such as the bathroom water tank and the swimming pool, simultaneously.

    Even the weather won’t hold you back with this kit as it contains a 4.5Kw electric heating element as a backup on bad weather days. Overall, this all-in-one kit is enough to serve the needs of a 4-person household.

    Duda Solar 20 Tube Water Heater Collector

    The heater comprises of water heater tubes that retain heat better than flat panels. Certified by SRCC, this system makes you eligible for a 30% federal tax rebate.

    The stainless steel pipes are made of food-grade material that is durable and efficient. The system is resistant to extreme weather and hailstorms. Also, the inner coating of the stainless steel tubes is built in a way that prevents the harmful accumulation of bacteria. The design ensures that water passing through the tubes maintains the desired qualities.

    Since the system is heavy, it is best installed by a team of professionals. Since it is equipped with a storage tank and controller, this solar hot water system is easy to use.

    Buying Guide

    When choosing a solar water heating system for your home, there are several that you must consider.

    Capacity of the System

    the system you pick should meet your needs. For instance, if you regularly require 500 gallons of water a day, make sure that the system you choose can fulfill these demands and more.

    Ease of Use

    When choosing a system, give it a once-over to ensure that it is easy to set up, use, and maintain. Doing so will help you avoid problems after making the purchase.  


    Since solar powered heaters are installed outside, they need to be durable and made of quality materials. Thus, choose a product that gives you the best value for your money while being equipped to withstand the vagaries of nature.

    Stephanie Colaco
    Stephanie Colaco

    Stephanie is a writer and editor, with a love for gadgets and all things solar. In her spare time, she enjoys reading and chasing unicorns with her 9-year-old.

    • John Gathuita

      John is an electrical and solar technician, writer, and blogger who specializes in renewable energy, sustainability, and technology. He seeks to inspire more people to adopt solar energy and to work towards a sustainable future.