the sun to heat water to be used in a home or other building. They typically can supply approximately 80-90% of a household’s water heating needs¹.
How do they work?
Solar water heaters work by converting sunlight into energy for heating water through the use of a solar thermal collector. The solar energy collector heats a fluid inside the heater that is then either pumped (“active” systems) or moved by natural convection (“passive” systems) into a hot water storage tank where the heat is then stored.
Storage tanks for solar water heaters are typically large in case there is bad weather and to ensure that enough hot water is available for use. The need for a larger sized tank is because the optimum final temperature for solar collector-generated heat is often lower than for conventional water heaters.
Types of solar water heaters
There are two general types of solar water heaters, passive SWHs and active SWHs. Both require an additional source such as an electric heating element or fuel oil central heating system that is activated when the tank falls below a particular low temperature threshold.
Combining solar water heaters with a backup heat source such as a wood stove chimney can allow these solar water heaters to be used year round while avoiding the use of fossil fuels or electricity to power them.
Passive SWHs are typically geared for warm weather climates. They require no electricity (will work even if there are blackouts) and can be installed yourself if you choose¹. To move the heat around, they rely on convection or heating the fluid in the system. They cost less than active systems and require little to no maintenance, but their efficiency is much less than an active system.
Active SWHs are available for both moderate and cold climates. These systems use electricity, but the cold climate active SWHs have special collectors that can be used in remote and off-grid situations with the right type of setup¹. They involve at least one pump that circulates the water or the heating fluid in the system. In addition to residential settings, such systems can also be used for commercial applications such as nursing homes, universities, and summer camps.
The type of solar water heating system that is required for a region essentially depends on how cold and hot it can typically get in that particular climate.
Why choose a solar water heater instead of a conventional water heater?
Solar water heaters¹:
- Can provide large energy savings with relatively low investment, and will pay for itself within approximately three to five years.
- A much lower lifetime operating cost than conventional water heaters because the energy from the sun is free.
- When using only solar energy, these systems eliminate the use of fossil fuels to heat water, reducing a homeowner’s carbon footprint.
- Increase the value of a home.
- In passive SWH systems, you can have hot water even if the electricity goes out.
- Helps to protect from future energy bill rate increases.
- Rebates and other incentives may be available to help cover the cost of purchase and installation. Be sure to check with your local energy company and municipality to find out if any of these resources are available to you.
- Installation options include do-it-yourself kits and professional installations.
- Models are now available for just about any climate.