Evacuated Tubes
for Solar Hot Water Heating

Evacuated tubes

Buying tips of the evacuated tubes for solar hot water heaters. Exploring the advantages and benefits of tubular solar water heaters.

The evacuated tube system is a solar collector for water heating that uses vacuum glass tubes to absorb the heat from the sun. These single collectors have two layers of glass, joined together, absorbing film and vacuum between to prevent heat loss from the absorber.

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These single solar tubes are combined into groups, supported by the frame and manifold or water tank at the top.

Evacuated solar tubes are usually connected to the manifold to allow easy installation and replacement (plug-and-play principle).


The main advantage of the evacuated solar tube water heaters is the ability to heat water even during cloudy days.

Because of the cylindrical shape, the evacuated tube system is facing the sun all the time and therefore is more efficient than flat solar panels. As long as the sun shines, the evacuated solar tube heater can be in service all year round.

You can use this system even in a cold climate, as the selective coating and vacuum layer prevent heat loss and ensure high energy absorption.

Since the heat pipes transfer the heat in one direction only and within the collector, over 92% of the heat is absorbed, and less than 8% is heat loss.

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How evacuated tubes work

When the evacuated solar tube is exposed to the sun, it absorbs the heat. The heat tube located within the evacuated glass tube gets warmer, and the liquid (alcohol, acetone) in the heat tube quickly turns to hot vapor.

The steam or hot vapor rises to the top of the heat pipe. The cold water or glycol flows through the manifold and picks up the heat.

The fluid in the heat pipe gets colder and condenses (turns into the liquid), and goes down to the base of the heat pipe. The cycle starts again and continues until the solar tube system has enough sunlight or diffuse light. Recommended tilt angle should be maintained.


  • The evacuated solar tube system provides free solar water heating, reducing your utility bills significantly.
  • This solar water heater provides an easy DIY installation.
  • High efficiency as the heat is transferred only one way.
  • High transfer rate with the use of copper tubes.
  • High absorption when using the vacuum and special absorption film.
  • Can operate in colder climates.
  • Works great in overcast or diffuse sunlight conditions.
  • An evacuated solar tube doesn't need maintenance.
  • Broken tubes can be easily replaced.
  • It is built to last.

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