Solar Water Heater: A Complete Guide

What is a solar water heater, is it worth it? This blog explores how a solar water heater can make a difference in your energy consumption.

When most people think of switching to renewable energy sources for their homes, they tend to mainly consider electricity-producing solar panels. 

And while these can make a huge difference in your electricity bills and carbon footprint, a solar water heater system can often work out a lot cheaper. 

Unlike solar panels, there are quite a few different solar water heaters, and that can make it a bit confusing to find the type that will work best for your home. 

So, before you just pick the first one you see advertised, let me give you an easy-to-understand overview of what these systems are all about. 

What Is A Solar Water Heater?

A solar water heater is a system that harnesses the heat of the sun's rays and transfers that heat directly to water or a heat-exchange liquid. The heated fluid then circulates through flat panels, where it heats up and flows back into a storage tank. 

The main part of solar water heaters is black panels that you would usually install on a south-facing roof to maximize sun exposure. It’s also important to note that this area of your roof should not get a lot of shade during the day. 

The more sun exposure you get on these panels, the better. 

solar water heater

Compared to a traditional water heating storage tank, you’ll only be using electricity to pump the fluid around the system. You’ll be taking advantage of the free energy that the sun provides. 

Most people who install such systems do so for the energy efficiency they gain, and it can take you a long way towards off-the-grid living. A solar hot water system is also suitable for both heating your water for use in the home, as well as heating a pool, which can also give you a huge cost saving. 

Where things get a bit more complicated is when it comes to the exact technical functions. See, there are active and passive systems, and not only do they function differently, but they have significantly different price ranges. 

More on this shortly. 

How Do Solar Hot Water Heaters Work? 

Let’s take a closer look at the components that make up a solar water heating system and how they all tie together to create plenty of hot water for your home. 

Collectors

The so-called collectors are black panels that you typically install on your roof where they get a lot of sun exposure. They are very different from photovoltaic panels that most people are familiar with. 

These collectors are designed to track thermal heat from the sun rather than create an electrical current that you can use for all types of household appliances or charge batteries. 

The black panels have a system of tubes running through them, and as the sun heats up the panel’s absorber plate, that heat transfers to a fluid in the pipes. 

Just like with PV solar panels, these solar hot water heaters come in different sizes, and the more hot water you need, the more panels you would install. 

Solar panel vs A Collector of a solar water heater

Heat Exchanger

The collector gradually heats up the fluid, and temperature sensors will measure that increase. Once the temperature reaches a critical point, the heat exchanger pump starts to circulate the fluid into your storage. 

This is a clever part of solar hot water systems, as the fluid circulates through a spiral system of pipes within the storage tank to transfer the heat from the fluid to create hot water in the tank. 

Hot Water Storage Tank 

The size of the hot water tank in a solar water heater system will usually depend on the size of the solar water heating units on the roof. The more units you install, the more hot water you can store and the larger you want the storage tank to be. 

At the same time, if you don’t have space for a large tank, then it might not be cost-efficient to install multiple units on your roof. 

Controller System

The controller system does two things. 

First of all, it monitors the temperature in the panels, and when this reaches a critical point, pumps lick in to circulate the fluid through the heat exchanger. 

This ensures maximum efficiency, especially in cold weather. 

The second thing the controller unit does is monitor the temperature inside your hot water tank. It’s part of a safety mechanism to avoid the tank overheating. But it also helps to avoid pumping heat transfer fluid that is colder than the hot water in the tank. 

Backup Heater

The final thing your solar water heater will have is some sort of electrical backup heating system. As well as these systems work, even with reduced sunshine in winter, most people will likely have many days or weeks where they simply don’t get enough sunshine. 

On those days, you would use the backup system for hot water. How often you use it will depend on your local climate. 

solar water heater working diagram

Types Of Solar Water Heating Systems

There are two main types of solar water heater systems, and within these passive and active systems, there are slightly different methods of heating water. 

Let’s take a closer look at each solar water heater type so that you know the basics for choosing the right system for your home. 

1. Active Solar Water Heaters

Active solar water heaters come as direct and indirect systems. And it’s important to understand the limitations as they could impact how effective they might be in your geographic location. 

a) Active Direct Systems

Active systems with direct heat transfer are based on the concept of circulating potable water directly through the roof panels. This water heats up, and the active system then pumps the hot water into a storage tank. 

While this kind of setup is generally cheaper to buy and maintain, it’s only suitable for mild climates. If there’s any chance of freezing temperatures where you live, then a direct active system could completely freeze up, and the pipes could burst. 

That’s one mess and expense you don’t want to deal with. 

b) Active Indirect Systems

An active indirect system, on the other hand, is based on circulating an antifreeze fluid through the pipes. As it heats up in the panels, the active system then pumps the fluid through a set of pipes into a heat exchanger. 

This spiral pipe system is inside the tank, where the heat from the antifreeze fluid transfers to the water inside the tank. 

This is one of the most common active systems and is suitable for both mild and cold climates. The fluid won’t freeze, and you can still generate hot water on clear winter days. 

solar water heater

2. Passive Solar Water Heaters

Passive solar water heaters also come in two different configurations. Many people are tempted by the lower price and up-front costs of a passive system, but it’s important to note here that these systems are less efficient. 

a) Integral Collector Storage 

An integral collector storage (ICS) system is based on the collector panels also functioning as the storage solution for the hot water. These passive systems rely on gravity to then circulate the hot water to your taps, which means there are no controller units or pumps to complicate the passive system. 

The downside is that they are liable to freeze in cold weather, so you would have to drain them for winter to avoid the storage tank bursting. 

The other downside is their overall weight. You may need to reinforce your roof to hold 

They tend to be common systems not for potable hot water but as a way to pre-heat water for a central heating system. 

b) Thermosyphon Water Heaters

This is a similar setup to an ICS passive solar water heater, but it takes more advantage of the gravitational effect and thermo circulation. 

In this passive system, water heats up in the panels and rises into a storage tank that has to be higher than the panels. As the hot water flows up, colder water flows down into the panels. 

It creates a circulation system based on the laws of physics.

This kind of solar heating system is more efficient than an ICS, but it has the same downsides when it comes to freezing conditions and the weight of the storage. 

How To Choose The Perfect Solar Water Heater For Your Home? 

Here are the main things you have to consider when you’re trying to choose a solar water heater system and not get blinded by fancy advertising material and clever salespeople. 

Volume Of Hot Water

The first thing you need to work out is how much hot water you need on a daily basis. If you live in a household of just two people, that number will be very different from a family of five. 

One way to work this out is to keep a journal of how often you use central or electric water heaters. And If you want to get very detailed data, then write down how often you fill the kitchen sink, wash your hands, and take showers. 

Once you know how much hot water you use, then you can determine the size of the solar water heater and storage tank. 

Geographic Location

If you live in South Florida or Arizona, where you practically never have freezing weather conditions, then you might be able to save some money by investing in passive systems. 

For more details, see the section above, but they basically involve heating up potable water rather than a transfer fluid. 

The other thing to keep in mind is that if you live somewhere that has a lot of clear blue skies throughout the year, then you probably won’t need as many panels in your solar hot water system. 

But if it’s regularly cloudy and you have long and dark winter months, then a few extra panels could make the difference of having plenty of supply. 

Orientation Of Your Roof

This is a key part of installing a solar hot water heater. Ideally, you need a part of your roof to be south-facing, where the panels would get the most amount of direct sunshine. 

However, in some cases, that isn't always possible. 

For example, the section of your roof that is south-facing may also get a lot of shade during the day. Or maybe that section happens to be very small. 

In those cases, you need to make sure that you install the most efficient solar heating system to get the maximum benefit.  

Budget

And finally, your budget will heavily influence what solar thermal systems you can consider. You will have to strike a careful balance between a larger but less efficient system and a smaller one that would have a higher solar energy factor. 

What I would also say is that when you’re making these renewable energy decisions, you should consider how much money they will save you in the future, which might allow you to increase your budget further. 

How Much Do Solar Hot Water Heaters Cost? 

Overall, the cost of a solar water heater system will depend on whether it’s an active or passive one and the number of panels you want to install. 

Let’s break that down a bit. 

Active Systems

An active solar water heater will generally cost a lot more than a passive one. And the total cost depends on how many panels you need and what size the water tank will be. 

As a typical guideline, you can expect the cost for an average home to be about $9,000 before state and federal incentives and tax rebates. 

Higher capacity systems for larger family homes would typically cost about $13,000, but they can often generate so much hot water that you save a fortune on electricity. 

solar water heater cost

Passive Systems

Passive solar water heaters are significantly cheaper than active ones. A typical passive solar hot water heater for a family home would start at about $4,000 and will store about 60 gallons of hot water. 

Keep in mind that while they are cheaper, they aren’t suitable for places where it freezes in winter. And the energy savings won’t be as great as with an active system. 

Also, keep in mind that integral collector storage systems might be cheaper, but you might end up with higher installation costs. If your roof isn’t suitable for supporting the weight of such a system, then it may require further structural support. 

Consider Financing Options

One thing to consider is pushing your budget to a system that maximizes your hot water production by financing the purchase. If you’re buying or building a new home, then consider adding the cost to your mortgage. 

Alternatively, look at multiple energy efficiency projects, including insulation that you can roll up into a refinancing deal. 

Some banks also offer discounted mortgage rates and loan options to finance renewable energy projects in your home.

For a good home solar system, it could mean paying just $10 more per month on a 30-year mortgage. You will more than save that on your reduced energy bills.  

Tax Rebates And Incentives Available For Solar Water Heating Systems

One of the most important things you need to keep in mind when pricing a solar water heater is that you will also be entitled to tax rebates on your investment

You can apply for a Clean Energy Tax Credit to cover part of the cost of your solar water heater equipment and installation. Let’s say you went with an active solar hot water heater, and it came to a total of $10,000. 

You can then apply for a tax credit worth 26% of the total costs. That means you would have a possible rebate of $2,600, which puts larger solar hot water systems in much closer reach for many households. 

Also, keep in mind that many states and municipalities have additional incentives and subsidies available. This could further reduce solar system installation costs.

Make sure you look up all your locally available green energy incentives for solar thermal systems before you make a final choice. You’ll be surprised how affordable larger systems become when you add up all the refunds. 

solar water heater tax rebate

What Are The Best Solar Water Heater Brands?

Here are three of the leading solar water heater brands that are available either directly or through local installation partners. 

Sunbank Solar

Sunbank is a leading manufacturer of passive solar water heating systems. They offer two sizes, with the smaller 40-gallon option starting at $2,500. The company also offers mounting brackets for flat roofs or ground installation options that give you more flexibility with the location of the panel.

SunEarth

SunEarth offers a wide range of panels and systems that include a hot water storage tank and everything you need for a highly efficient installation. You can also look at their options for solar PV panels to take an additional setup towards having a passive home. 

Apricus

Apricus has a choice of full home solar system configurations. These include active solar water heaters, as well as passive ones with flat plate collectors. The company also offers installation services and full consultation to determine the best solution for your home and budget. 

DIY Solar Hot Water System: Can You Build Your Own?

Yes, you can build a DIY solar water heater with reasonably few resources. 

The first thing you will need to do is create or buy a table that will function as a tank to hold water. This will require some carpentry skills, but it can be a lot of fun. The blow video will give you an idea of what is involved. 

Once you have the table set up, you need to paint it with black water-resistant paint. The reason it’s black is that it will absorb the maximum amount of heat from the sun to make the whole system a lot more efficient. 

The next stage is the most time-consuming and tricky. You will need to install a spiral of black plastic water tubing onto the table. It’s a two-person job, and you’ll need to secure the tubing to the table with zip ties. 

Each end of the water tubing needs to come out of one side of the table, where it would then be connected to a circular pump and water storage system. 

The last step involves adding a plastic cover to the table to avoid rain water getting onto the tubing. It would be difficult to drain fully and would make the system a lot less efficient. 

Finally, you need a water pump that would circulate the water through the pipes and into a storage facility. 

This could be a small pool or jacuzzi or a water tank that you can link up to a faucet in your home. 

According to the video below, a system like this could heat water to 120 degrees even on a moderately warm day of 83 degrees. 

It’s not easy to create your own solar water heating systems, but it can be a fun project that would definitely improve your energy efficiency at a much lower cost of investment other than your time and effort. 

FAQ

Are solar water heaters worth it?

Yes, solar water heaters are worth it and can significantly reduce your energy consumption. In some homes, up to 20% of electricity usage and costs are linked to heating water, which presents a significant saving.

Do solar water heaters work in the winter?

No, solar water heaters don’t work at night. A good passive system will have a backup water heater if you don’t have enough hot water to keep you going. But unless there’s direct sunshine, they won’t generate energy.

Do solar water heaters work at night?

Yes, all Jackery power products use lithium batteries because they’re lightweight and can hold a lot of charge. They were actually the first company to produce off-grid lithium batteries back in 2015.

Do solar water heaters work on cloudy days?

Yes, solar water heaters can work on cloudy days, but they will be a lot less efficient. It also depends on how thick the cloud cover is to determine whether the panels will get hot enough to reach a critical point for heating the water.

How hot do solar water heaters get?

Solar water heaters can reach temperatures of over 170 degrees in perfect conditions. That is more than enough to generate plenty of hot water for use around your home.

How long do solar water heaters last?

Most modern solar water heaters can last over 20 years. However, this will require some regular maintenance to ensure that the fluid and pumps are working at optimum performance.

Conclusion

Installing a solar water heater can be a very cost-effective way to significantly reduce your electricity use throughout the year. 

These systems are cheaper to install than PV solar panels and can reduce your electricity use by up to 20%. The main decision will come from what kind of budget you have and where you live to decide on passive or active solar water heaters. 

If it regularly freezes in winter in your location, then an active system won’t be an option. But with passive systems, you’ll even be able to generate hot water on sunny winter days. 

Take this first step to make a major difference in your carbon footprint. 


Chris is one of GreenCitizen’s writers who has been a long-time advocate of individual responsibility when it comes to the environment. He shares GreenCitizen's passion for making the world a better place every day of the year.


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