Which Solar Water Heater is More Efficient, ETC, or FPC?

Wed, 30 Sep 2020

ETC vs FPC solar water heater

The solar water heater is a scientific innovation that has changed the way water heaters are used today. In a solar water heating system, a collector is an integral device, which heats the water by absorbing solar heat. There are two types of collectors namely, solar Flat Plate Collectors (FPC) and solar Evacuated Tube Collectors (ETC). In this post, we will be looking at the differences. 


Flat Plate Collectors (FPC) 

Using the greenhouse effect, the Flat Plate Collector converts solar energy from the sun into heat energy, which then is transferred to the water system in residential and commercial houses. The water is then used for bathing, washing, cooking, or cleaning.



This collector comprises of a large sheet of the copper or aluminium absorbing plate. They are painted black so that the surface absorb as much solar energy as possible. Tubes or pipes (made of copper), which transfers the heated fluid, are lined and soldered across the surface of the absorber plates. As the plates are heated, the heat is absorbed by the fluid in the pipes, which gets circulated in the house. To minimize heat loss the absorber plates and pipes are enclosed in an insulated metal or wooden box. Inside the insulating material is a sheet of glazing material that does not significantly absorb the thermal energy.



  • Low Maintenance: Flat Plate Collector functioning requires less maintenance to keep it running effectively. The collector when installed outside is more reliable to withstand harsh weather conditions.

  • Reliability: The solar Flat Plate Collector is more effective at delivering the desired quantity of heated water at the needed temperature. This is one of the reasons why it is highly in demand in many houses.

  • Easy Construction: The construction is easy because of the simple stationary design. The collector box is designed in a way to keep the water sufficiently heated. 



  • The Flat Plate Collector lacks optical concentration. Because of this, there is usually a huge heat energy loss. Also, the high temperature of the water cannot be reached and consequently, collection efficiency is low.

  • The plate collectors are flat and because of this, they operate efficiently when the sun is overhead.


Evacuated Tube Collectors (ETC)

Evacuated Tube Collectors (ETC) consist of a heat pipe inside a vacuum heat tube and they function differently from Flat Plate Collectors.



The Evacuated Tube Collectors (ETC) comprises a row of parallel transparent tubes. Supported on a frame, they are connected to a header pipe. The header pipe is used in place of a blackened absorbing plate used in Flat Plate Collectors.

The glass tubes are cylindrical and built to deal with the issue associated with the flat absorbing plates of Flat Plate Collectors. Unlike FPC, Evacuated Tube Collectors (ETC) do not heat up the water directly. The vacuum tubes have the air removed within the frame in order to reduce heat loss. This way, evacuated tube collectors collect enough heat energy to heat water. They are normally installed in cold and wintry areas. 



  • It is easy to install. The manufacturing of Evacuated Tube Collectors (ETC) allows for easy installation. It takes less time to install and users can start enjoying its benefits.

  • There is less heat loss. Because the absorbing plates are cylindrical, Evacuated Tube Collectors (ETC) absorb heat energy from the surrounding weather reaching the required temperature quicker than Flat Plate Collectors. They can extract heat out of a humid atmosphere and do not need direct sunlight to function.

  • The transparent tubes guarantee the efficiency is high and offers better performance even when the sun is not at a suitable angle.

  • Due to the simple configuration of Evacuated Tube Collectors (ETC), heated water is optimally circulated. 

  • It has low maintenance. The components of Evacuated Tube Collectors (ETC) are designed to withstand unfavourable weather conditions. For this reason, they can be installed in areas of extreme weather conditions for water heating. 



The downside of using Evacuated Tube Collectors (ETC) is that the panels can be expensive compared to Flat Plate Collectors. This is because of their capacity to extract heat out of humid air in chilly areas. 


In a Nutshell  

Evacuated Tube Collectors (ETC) works better than Flat Plate Collectors (FPC) as they are cost-effective, easier to install, has low maintenance costs, and can extract heat energy from humid areas. If you desire a solar water heating system with a collector that can be relied upon at all times, go for Evacuated Tube Collectors (ETC). For more information, feel free to get in touch with us