Solar Water Heaters Explained: Are They Worth It?
Solar water heaters are rising in popularity across the United States. Also known as solar domestic hot water systems, solar water heaters could be a cost-effective way to create hot water for your home.
Like other solar devices, solar water heaters take energy from the sun and convert that energy into something usable – like hot water. Sunlight hits your home every day and goes to waste. Solar water heaters allow you to capture some of that energy.
How do solar water heaters work? Are solar water heaters worth it? Keep reading to discover everything you need to know about solar water heaters and their effects.
What Are Solar Water Heaters?
Solar water heaters consist of two main components, including:
- Storage tanks
- Solar collectors
With direct solar water heater systems, sunlight directly heats the water before the system circulates hot water throughout your home.
With indirect solar water heater systems, sunlight heats a special transfer fluid, which travels to your water tank to heat the water inside the tank.
You can buy an active solar water heating system, which uses circulating pumps and controls. Or, you can use a passive solar water heating system, which has no circulating pumps or controls. Most home water heating systems are active systems.
How Do Solar Water Heaters Work?
Solar water heaters work in different ways. However, the fundamental technology behind a solar water heater remains the same:
- Solar water heaters use solar collectors to gather energy from the sun (via the heat of the sun).
- A pump circulates transfer fluid (typically antifreeze or potable water) to the solar collectors, allowing the fluid to absorb energy from the sun (in the form of heat), heating the water.
- The fluid flows towards the insulated solar storage tank, reaching the heat exchanger inside the tank. The fluid heats the coils of the heat exchanger, warming the water inside the tank.
- The preheated water flows through your home’s ordinary water heater. Your water heater creates any additional hot water as needed for the task.
- You enjoy hot water around the clock. Even if your solar water heater system isn’t running at maximum capacity (say, after a long period of heavy usage), your water heater allows you to continue enjoying water throughout the day.
Most homes have a combination of a solar water heater and a conventional water heater. However, someone living off the grid or in an eco-conscious home may exclusively use a solar water heater for their water needs.
Parts of a Solar Water Heater
Solar water heaters work using several crucial components, including:
Collectors: Solar water heaters have panels known as collectors. You install these collectors on a roof. They’re different from ordinary solar panels. Instead of using the sun’s energy to generate electricity, collectors collect the sun’s energy as heat. As sunlight hits the collectors, it passes through the glass covering to hit the absorber plate. This plate has a special coating that captures heat from the sun. Depending on your household energy usage, you can choose the size and number of collectors to install. You can also choose whether you want a flat plate or evacuated tube collector.
Transfer Fluid: After the heater heats the absorber plate, the system transfers heat to a transfer fluid (which is generally antifreeze or potable water). The transfer fluid reaches the absorber plate through a series of small pipes.
Heat Exchanger: Transfer fluid travels from the collectors to the heat exchanger, which is a series of pipes located inside your storage tank. As the heat exchanger fills with the transfer fluid, it transfers heat from the fluid to the water inside your tank, creating hot water.
Storage Tank: Water sits inside the storage tank while waiting to be heated. The storage tank has a heat exchanger to heat the water inside.
Controller System: Modern solar water heating systems have a heat control system to prevent the tank from overheating. Controller systems also prevent cold water from cycling through your system if the panels aren’t working.
Backup Heater: Most households with solar water heaters also have a backup heater. A backup heater helps you continue to enjoy hot water even if your collectors are unable to collect solar energy. With most solar heating systems, you can expect about 20% of your heated water to come from a backup heater, which is often just an ordinary water heater.
Types of Active Solar Water Heating Systems
There are two main types of active solar water heating systems, including:
Direct Circulation Systems: Direct circulation systems use pumps to circulate household water through the solar collectors and into the home. They’re best used in climates where temperatures rarely drop below zero.
Indirect Circulation Systems: Indirect circulation systems pump non-freezing heat-transfer fluid through the solar collectors and a heat exchange. The collectors and heat exchanger transfer heat to the water, and the pumps circulate that heated water back into the home. If you live in a climate with freezing temperatures, then an indirect circulation system works best.
Types of Passive Solar Water Heating Systems
Passive solar water heating systems are less advanced than active systems. Instead of featuring circulating pumps and controls, passive systems use storage systems and basic fluid dynamics to pass heated water through your home.
The two main types of passive solar water heating systems include:
Integral Collector-Storage Passive Systems: These systems are ideal for areas where temperatures rarely drop below freezing. The system collects water throughout the day, making it ideal for households that use a significant amount of water during the day and evening.
Thermosyphon Systems: Thermosyphon systems use fluid dynamics to direct heated water through the system. Warm water rises and cooler water sinks. Passive systems have a collector installed below the storage tank. Warm water rises into the tank, while cooler water sinks into the collector.
Direct vs. Indirect Solar Water Heaters
You also need to decide whether you want a direct or indirect solar water heater.
In an indirect solar water heater system, the system collects solar energy and holds that energy in a special antifreeze fluid. This antifreeze is circulated into your hot water storage tank’s heat exchanger, heating the water for use in your home.
With a direct solar water heater system, the system heats water directly from the sun without the use of a transfer fluid. The sunlight directly heats the water, and the water circulates throughout your home.
How Much Do Solar Water Heaters Cost?
Solar water heater systems cost anywhere from $1,600 to $6,000. The average solar water heater system costs around $4,042.
With higher-end solar water heater systems, you could spend over $15,000 for installation, components, and equipment.
The larger your home and the greater your household water needs, the more you’ll need to spend on a solar water heater.
Others Things to Know About the Cost of Solar Water Heaters
When deciding whether or not to install a solar water heater in your home, there are other things to consider, including:
Your Roof Needs to Be in Good Condition: Installing solar collectors on a roof that’s in poor condition is not a good idea. When installing your solar water heating system, your roof needs to be in good shape and strong enough to support it. If you have an older roof, you may want to replace it before installing the collectors.
You Need Sunlight: This tip is obvious, yet some homeowners overlook it. When installing a solar water heating system, your roof needs to be exposed to sunlight. If you have too many trees, it might not work. Ideally, the sun will hit the portion of your roof covered by solar collectors during most daylight hours.
They Last 20 to 25 Years: A good solar water heating system will last 20 to 25 years with proper installation and maintenance.
They Require Little Maintenance: Solar water heaters require surprisingly little maintenance when installed properly. Even with minimal maintenance, the system should last 20 to 25 years.
Reduce Water Usage to Maximize Cost Savings: If you’re installing a solar water heater, then you should consider installing other devices to minimize water usage. Low-flow toilets, energy-efficient washers and dishwashers, low-flow showers, and other devices, for example, can significantly reduce household water consumption.
Final Word – Solar Water Heaters
A good solar water heater can almost entirely eliminate your water heating bill. When installed properly in the right climate, a solar water heater lasts 20 to 25 years and minimizes your reliance on a conventional water heater.
To decide if a solar water heater is the right choice for you, consider everything listed above.