Evacuated Tube Collector and Flat Plate Collector in a Solar Heater

Solar Water Heaters: Difference between Evacuated Tube Collector and Flat Plate Collector

As you might be aware, solar water heaters absorb the rays of the sun to heat the water. In order to perform this function, solar heaters are equipped with collectors.

Primarily, there are two types of collectors that are used in solar water heaters – Evacuated Tube Collectors and Flat Plate Collectors.

Evacuated tube collectors have a few glass tubes arranged in parallel rows. Each tube is made up of two glass walls, and the air between them is removed to create a vacuum which prevents heat loss. Due to this structure, evacuated tube collectors are highly efficient.

Flat plate collectors are one of the oldest types of collectors. They consist of an absorber plate to collect the diffused sunlight and an insulated metal box to retain the heat. The heat absorbed form the environment is transferred to a liquid that circulates within the copper pipes. And that’s how such collectors function.

In this blog, we will draw a comparison between both these types of collectors. We will also help you understand which is better according to your needs.

Evacuated Tube Collector V/S Flat Plate Collector

Both Evacuated Tube Collectors and Flat Plate Collectors offer a unique set of benefits. In this section, we’ll compare the two based on the key parameters.

1. Cost


When it comes to the cost of purchase, evacuated tube collectors are slightly more expensive as compared to the flat plate collectors. This is because flat plate collectors are easier to manufacture and simpler to design. On the other hand, evacuated tube collectors have a lower cost per BTU (British Thermal Unit). BTU means the amount of energy required to raise the temperature of 1 pound of water by 1 degree Fahrenheit.

2. Performance

Performance of Water Heater

Evacuated tube collectors are more efficient in retaining heat, thus they perform well even in low temperatures. On the other hand, flat plate collectors may not be able to supply hot water in winters.

Evacuated tube collectors heat water faster and can provide you with hot water at up to 200 degrees Fahrenheit. Thus, their heating efficiency is excellent. That means they are suitable for commercial applications that require hot water in large quantities.

Flat plate collectors may take longer time to heat water and can supply hot water at up to 140 degrees Fahrenheit. Thus, they are suitable for homes that do not require large quantities of hot water.

3. Durability

Durability of Water Heater

Both evacuated tube collectors and flat plate collectors are expected to last for about ten to fifteen years.

As flat plate collectors are made up of copper pipes, they are more vulnerable to corrosion. The condensation of water on the inside of the glazed plate and repeated drips on the solar absorber can affect the durability of the collector. It can also lead to growth of mould. However, in most cases, flat plate collectors can easily be repaired.

When it comes to evacuated tube collectors, their heating efficiency depends on the vacuum. In case an evacuated tube collector loses its vacuum, the glass tubes will need to be replaced.

4. Installation

Water Heater Installation Support

As evacuated tubes are cylindrical in shape, they receive the sun rays at 90 degrees throughout the day. Thus, their absorption is optimum, no matter the way in which they are installed.

Due to their design, the flat plate collectors receive optimum sunlight only during midday. Thus, they need to be installed in a slanting position at a specific angle.

Which is better: Evacuated Tube Collector or Flat Plate Collector?

When it comes to colder areas that witness snowfall for the most part of the year, evacuated tube collectors are an excellent choice. They can supply hot water efficiently even when the temperature is extremely low.

On the other hand, flat plate collectors are recommended for tropical climates where the days are usually sunny.


Whether you need a solar water heater with an evacuated tube collector or one with a flat plate collector, Racold is your one-stop solution. We offer a wide range of solar water heaters that are designed according to international standards for delivering superior performance. So, wait no more. Visit the product section of this website to check out all the solar heater models now.

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