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Solar Water Heaters: Definition, Pros, Cons, and Alternatives

The words "Solar Water Heaters" over an image of a solar water heater on the roof of a home, turning the sun's energy into hot water.
PublishedFebruary 15, 2024
UpdatedMay 7, 2024
AuthorBrian ChurchWriterEditorCory O'Brien HeadshotCory O'BrienSenior Director - Growth Marketing
In this article
What are solar water heaters?
How do solar water heaters work?
Solar Water Heater Advantages & Disadvantages
Key Takeaways for Solar Water Heaters

The sun’s energy provides the power we need to accomplish so much in life – from growing crops to generating electricity and even helping our bodies produce vitamin D.

While people have been harnessing the energy from the sun to heat water since the dawn of man, many modern solar water heating technologies and techniques can be used today to efficiently heat your home’s water supply with emission-free solar power.

In this article, we will break down everything you need to know about solar water heaters to help you determine if one is worth it for your property.

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What are solar water heaters?

Sometimes called solar domestic hot water systems, solar water heaters are a cost-effective way to heat a residential property’s water supply with the power of the sun. Most solar water heaters harness the sun’s thermal (or heat) energy by directly allowing sunlight to warm an outdoor water supply or by using special solar thermal energy collectors.

Here – it is important to know that thermal solar collectors are distinctly different from the photovoltaic (PV) solar energy systems that Palmetto supplies homeowners to generate electricity and save on utility power costs.

Although you can heat your water with the electricity generated by PV solar panels (we will get into more detail about this later), self-contained thermal solar water heaters are another great way to go green and save money on monthly energy expenses.

Read more: What is Solar Energy?

How do solar water heaters work?

Solar water heating systems come in many shapes and sizes. More than anything, however,  the distinction between an active and passive solar water heater is the most important to understand.

Pardon the pun, but knowing the difference between a passive and an active solar water heating system can prevent you from getting into “hot water” later if you invest in the wrong technology for your home or climate.

Active vs. Passive Solar Water Heaters

Passive solar water heating is about as simple and green as it gets. It is a purely solar-powered water heating system that lacks moving parts, additional energy resources, and significant upfront costs. A typical passive solar water heater consists of not much more than a large rooftop tank (known as a batch collector), where the water is warmed by the sun before flowing into your home’s plumbing system.

Although less efficient and effective than their active system counterparts, passive solar water heaters are often feasible solutions for warm climate areas that rarely experience below-freezing temperatures. Relying on daily sunshine to heat the water tank, passive solar water heaters are generally better at delivering hot water towards the end of the day, rather than in the morning.

Despite higher costs, active solar water heaters are the most common solar water heating appliances installed in the US because they are much more efficient than passive systems. By definition, active solar water heaters add an “active” element to the water heating process with an electric pump and valve controls to push either water or a heat-exchanging liquid throughout the entire system.

Here, an active direct solar water heater warms your home’s water directly with the sun. In contrast, an active indirect solar water heater uses the sun to warm a separate fluid before transferring the heat from that fluid to your water supply. By keeping your water indoors, active indirect solar water heaters are the preferred technology for climates that frequently dip below freezing temperatures.

When paired with a photovoltaic (PV) solar system to save money on electricity, active solar water heaters can be powered by the sun in two separate ways – by collecting heat through its thermal components and operating the pump controls with solar electricity.

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Solar Water Heater Advantages & Disadvantages

Compared to conventional water heating systems, solar water heaters can bring your home into a greener and more efficient future full of energy cost savings. With that said, solar water heater savings aren’t the same for everyone and may be more trouble than they are worth for those without excessive water heating costs.

To get an idea of the general pros and cons of solar water heaters, please see the table below.

Solar Water Heater Advantages Solar Water Heater Disadvantages
Powered by solar energy, with no ongoing fuel costs or carbon emissions from fossil fuels Higher upfront costs than most conventional water heating systems
Capable of partial or entirely off-grid operation to reduce utility energy spending Almost always must be supplemented with grid energy or a backup source of power
A reliable source of hot water in all American climates Shorter expected lifespan than PV solar panel systems
May qualify for several green energy financial incentives and rebates Operational cost savings are directly tied to the availability of sunlight – daily and seasonally
Synergistic financial and environmental impact when paired with PV solar panels Can require a large amount of roof and indoor space for system components

Are solar hot water heaters worth it?

If the sun shines on your roof and there is room for a few thermal energy collectors, solar hot water heaters are almost always worth it to save money on long-term energy costs with a sustainable, green power source. In the US, you may be able to reduce your total solar water heater installation costs by up to 30% with federal clean energy tax credits as well as any other rebates or incentives that may be available in your state, city, or utility service area.

While an excellent idea for many, whether or not solar water heaters are the absolute best choice for your home depends on several unique factors, including your local climate, the other energy systems on your property, and your personal hot water demand.

Before moving forward with installing a solar water heater, we recommend evaluating all your hot water options to find the most energy-efficient (and cost-saving) solution.

Solar Hot Water vs. Conventional Water Heaters

Conventional water heaters, also known as storage water heaters, are very similar to the solar systems we’ve covered in this article, with the sole difference being the energy source. While solar hot water systems can utilize cost and emission-free solar power, most conventional water heaters run solely using natural gas or electricity, usually supplied from the power grid.

ENERGY STAR reports that homeowners can cut their annual hot water costs in half compared to conventional water heating systems by switching to a solar water heater. Today, many solar hot water heaters can be classified as hybrid systems – in that they use a secondary source of power (like natural gas or electricity) to boost performance on cold mornings, overcast or cloudy days, or whenever solar thermal alone is not enough to meet home hot water demands.

Solar Hot Water vs. Energy-Efficient Water Heaters

Of course, thermal solar hot water heaters are not the only technology on the market that could be used to help reduce your hot water energy consumption and costs. For instance, heat pump water heaters can capture heat from the air surrounding your home and transfer it (at higher temperatures) to your water tank – a practical solution primarily for those located in warmer climates.

Note: Heat pumps are also a popular furnace and air conditioning alternative to maintain comfortable indoor temperatures efficiently. Read more about residential heat pumps for heating and cooling.

Besides heat pumps, tankless water heaters can also help you reduce unnecessary power use by heating water on demand instead of constantly using energy to maintain high temperatures in a large storage tank. Especially when combined with a PV system to generate the necessary electricity, high-efficiency hybrid or electric water heaters are a great energy-saving solar water heater alternative to stay green and keep your hot water heating costs low.

Key Takeaways for Solar Water Heaters

To summarize, let’s look at a few of the most important aspects of solar water heaters that we’ve discussed above. Your key takeaways should include:

  • Solar water heaters harness the sun’s thermal energy to heat your home’s water supply.
  • Active indirect solar water heaters are the most common solar water heating systems used to deliver year-round, reliable hot water in most American climates.
  • Solar water heaters save homeowners money on energy costs compared to conventional hot water systems and will usually qualify buyers for several financial incentives.
  • Before purchasing a solar water heater, consider weighing its costs and energy efficiency against other technologies, such as tankless or heat pump systems.

If you’re unsure whether a solar water heater should be the next development for your home’s energy sustainability and lowering your carbon footprint, we are here to help. Please do not hesitate to contact an expert at Palmetto today and discuss your solar energy options.

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About the AuthorBrian ChurchWriter

Brian is a writer, NABCEP PV associate and outdoor enthusiast living in Denver, Colorado. As a freelancer, Brian has written hundreds of articles to help individuals, businesses and our planet benefit from solar power and sustainable energy systems.

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