A guide to solar hot water systems



Cleaner energy and cheaper bills — these are just a couple of the benefits a solar hot water system brings to your home. It’s also why many homeowners are adopting a greener, solar approach.

Research by the Solar Energy Industries Association shows that homeowners will start using more and more solar energy. Solar energy consumption could increase by 42% in the next three years.

Alongside the environmental benefits of solar water heaters, these systems pay back their value in as little as three to five years.

If you’re considering buying a solar hot water system, you’ve come to the right place. Read on to learn more about solar hot water systems, the types of systems available, how to choose the right system for your home, and whether you need a professional to install it.


How a solar hot water system works

Solar hot water systems absorb and use the sun's thermal energy to heat the water in your home. A solar hot water system consists of five main parts: 

  • Solar collectors
  • Heat exchanger
  • Storage tank
  • Controller system
  • Backup heater

Let’s take a look at the function of each component. 


Collectors refer to the panels on a solar thermal system. These are usually installed on a rooftop. Solar collectors differ from photovoltaic solar panels because they generate heat instead of electricity. Thermal energy passes through the solar collectors in the form of sunshine and hits an absorber plate. Absorber plates are flat plates with grooves typically made of copper, stainless steel or plastic.

The absorber plate has a coating that traps the sun’s radiation and converts it into heat. Small pipes in the plate transport this heat to a “transfer fluid.” Transfer fluids transfer heat to the storage tanks in your solar water heating system. 

Collectors are available in a variety of sizes. The number of collectors needed is determined by how much sunlight your roof receives and how much hot water you use. Collectors come in two different designs: flat plate and evacuated tube. Flat plate collectors are usually cheaper but absorb less solar power and aren't as effective at low temperatures. Evacuated tube collectors take up less area but are heavier and more brittle.

Heat exchanger and storage tank

When the transfer fluid in your collectors gets hot, it passes through a network of pipes known as a heat exchanger. Since these pipes are full of heat transfer fluid, the heat from the pipe is transferred to the water in your home, resulting in hot, ready-to-use water.

Controller system

A controller system ensures that the water in your storage tank doesn't overheat. It also prevents external cold water from entering your solar hot water system, ensuring the transfer fluid stays heated. Controller systems are useful during the colder months of the year.

Backup heater

Your solar hot water system comes with a backup heater system. When the weather isn't suitable to create enough hot water from solar radiation, your backup heater will switch on and heat water using gas or electricity. Your backup heater will only be used for 20% to 50% of the year, saving you money on water and electricity bills.


Types of solar water heaters

Although all solar hot water systems have the same fundamental components, there are a few minor design changes depending on your chosen brand or manufacturer.

Direct and indirect solar hot water systems affect how the heat transfer fluid in the collectors is heated. You must also choose between an active or passive system, affecting how the transfer fluid passes through pipes.

Read on to learn the differences between the types of solar water heaters. 

Direct vs. indirect solar water heaters

An indirect solar hot water system captures solar energy, storing it in an antifreeze fluid. The antifreeze pumps into your hot water storage tank, which warms the water used in your home. On the other hand, a direct system receives sunlight directly to heat your water instead of being collected in a transfer fluid.

Most American homes use indirect solar hot water systems. This is due to an indirect system’s ability to withstand colder weather, making it better at preserving heat during colder months. However, indirect hot water systems tend to be more expensive than direct solar hot water systems.

Some households in southern parts of the country prefer using direct solar hot water systems. However, while more expensive, an indirect system will help reduce efficiency losses, saving on bills and avoiding backup usage. 

Active vs. passive solar water heaters

The antifreeze fluid in your solar hot water system uses a controller heat pump or gravity to travel through the system's pipes. Active solar hot water systems use controller pumps, while passive systems solely rely on gravity to move the antifreeze fluid around.

While passive systems are easier to set up, they aren’t as effective in comparison to active ones. Moreover, some passive systems require you to move your storage tank to a location higher than the collectors, which can put a strain on your roof. In the United States, the majority of solar hot water heating systems are active, which means they feature a controller pump to help move the antifreeze fluid.


Selecting the right solar water heater for your home

You must consider factors like how much sunlight your house gets, the amount of hot water your household uses regularly, and your budget. When looking for solar water heaters, search for the Solar Rating and Certification Corporation (SRCC) ratings. SRCC ratings make it simple to compare various brands and models using third-party professional data.

Because each home is different, get professional advice to ensure you select the best solar hot water system for your needs. Speak with a local solar installer or a professional to know more about the system recommended for your home.

Let’s review a few things to know before deciding to install a solar hot water heating system.


Are solar water heaters worth it?

You must consider that solar water heaters rely on an energy source that is only available for half the day. This can also differ depending on your location and the time of the year. For example, a solar water heater can be great for the summer, when it can heat up to 95% of your home’s water.

On the other hand, solar water heaters won’t be of much use on cloudy days due to the lack of sunlight. Instead, it could lead to heat loss. Hot water is different from solar-powered electricity; you can’t store it in batteries, so even the water in a storage tank can become cold after days without any solar power.

As a result, a solar water heater is not a replacement for your traditional water heater. Instead, it’s a handy add-on that can become a wise investment over time. While some models cost as much as $10,000 including installation, a solar water heater will gradually begin to pay for itself in the form of reduced electricity bills.

When your heater completes its solar payback period — which is relatively short — it will produce virtually free domestic hot water for the rest of its lifetime! Furthermore, solar hot water systems have low maintenance costs because they don't have any moving parts.

The cost of solar water heaters

Installing a solar water heater can reduce water utility bills by 50% to 80% on average. Furthermore, solar radiation is a free energy asset, so you don’t have to worry about price hikes, inflation or fuel shortages.

The economics of a solar water heater are much more appealing in new construction. In most cases, a solar water heater in a new 30-year mortgage costs between $13 to $20 per month. The federal income tax deduction for solar-related mortgage interest lowers this by another $3 to $5 monthly.

As a result, if your monthly fuel savings exceed $15, investing in a solar water heater pays for itself almost instantly. In a nutshell, you save more than you pay.

There are also certain incentives and rebates available for solar water heaters. A federal solar tax credit of 26% is available if you install a solar water heater. For example, if you buy a solar hot water system for $8,000, you'll get a $2,080 federal tax credit, reducing the total cost of your solar water heater to $5,920.

Installation and maintenance costs depend on the brand of solar water heater, the state you live in, and the company you hire to install your solar water heater.

The benefits of solar water heaters

Traditional water-heating systems are costly and use vast amounts of energy. Most of our energy comes from fossil fuels like natural gas and oil. These finite resources are depleting at an alarming rate.

Solar water heaters are a great way to cut bills while saving energy and precious resources. They pay back their value over time, and can significantly reduce your bills and carbon footprint, increasing your energy savings.

Let’s take a look at some more benefits of solar water heaters.

  • Zero-cost renewable energy. Your solar water heater heats your home's water using sunlight, a free natural resource. Unlike electric water heaters, you use a renewable energy source without paying a single penny for electricity or other energy bills. You may need to use a backup heater during winter, but investing in a solar water heater is a sustainable practice for most of the year.
  • Safe for the environment. A solar water heater is a green alternative to a conventional water heater. It doesn’t depend on fossil fuels, has zero carbon emissions and reduces your overall carbon footprint.
  • Low maintenance. A solar water heater requires little maintenance. It has no moving parts, resulting in a minimum degree of wear and tear. Furthermore, the average life span of a solar water heater is 20 years.


Installing and maintaining a solar hot water system

You should consider a few critical factors when installing a solar water heater. These include the amount of sunlight your home gets, the climate in your area, local building code requirements and safety concerns; consequently, it is essential to have your solar water heater installed by a skilled professional.

After installation, you'll need basic maintenance to keep your heater functioning effectively. Passive solar hot water systems require less maintenance. However, if you have an active system, study the owner's handbook and discuss your system's maintenance needs with a professional.

Since solar water systems don't have moving parts, maintenance checks can be done every three to five years. If your system has any electrical parts, it might need a component or two replaced every 10 years.

Solar water heater maintenance tips

Solar water heaters generally require little to no maintenance in the short term. However, these systems last an average of 20 years, so it would be a good idea to make periodic checks on your water heater.

Here are a few maintenance tips to keep your solar water heater running smoothly.

  • Check for leaks and loose connections. Check for leaks in the pipes, tank, panels and so on, as leaks are common in these sections of your solar water heater. Look for loose electrical connections and wires as well. Maintain a dust-free environment for the solar panels.
  • Drain components to prevent rust. Water constantly flows through your system's pipes, which could lead to corrosion. Some components can also freeze in cooler climates. Ensure you drain the collectors and pipes regularly to keep your solar water heater from freezing.
  • Clean your heater to prevent moss. Ensure you clean your system regularly to prevent any form of outgrowth.
  • Maintain your roof. Keep an eye on the bottom of your home's roof for any signs of water leaks from your solar water heater. Maintain sealant and flashing around your roof to prevent leakage or penetration.
  • Check your support structures. Tighten all screws and bolts connecting your solar water heater's collectors to any support structures. Keep an eye out for rust on steel parts. If you see any corrosion, clean and paint the parts as necessary.


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Thinking about getting a solar water heater? This all-in-one guide discusses the types, costs and benefits of solar water heaters.