In certain situations a flat plate collector is more suitable than evacuated tube solar water heater system, however, the choice between a flat plate and evacuated tube solar water heater systems, is usually a personal choice.

 

Evacuated Tube

Flat Plate Collectors

Evacuated Tube Solar Collectors on evacuated solar water heater systems are sealed within a vacuum-sealed glass tube. This eliminates convection and conduction heat losses, and also isolates the collectors from any adverse weather conditions. The collectors on a flat plate solar water heater system are built within a solid, sealed case and covered with a tough tempered glass facing. This helps to protect them from elements. The air gap between the absorption plate and the collector’s cover can lead to conduction and convection heat losses, especially on cold windy days.
Evacuated Tube solar water heater systems are carried to the job site, and onto the roof in pieces for a lighter, easier workload. Assembly must then still take place. Flat Plate Collectors on a flat plate solar water heater system must be installed in one solid unit, and must be brought to the job site and installed on the roof as such. Storing of a flat plate is easier. No assembly of the collector is required.
If one tube becomes damaged, only that tube needs to be replaced. Depending on the type of tube used, there is no need to shut the entire solar water heater system down. When a portion of a collector fails, the entire solar water heater system collector must be shut down and replaced.
Because of their 360-degree collector design, evacuated tube solar water heater system collectors are relatively adept at accepting most installation angles. Flat Plate Solar Collectors in a flat plate solar water heater system circulate water through insulated areas within the collector. This makes them more prone to leakage, corrosion and restricted flow.
Glass tubes are fragile and must be handled with care. Breakages are high if not handled correctly. Flat plates are not as fragile as the glass tubes and therefore not prone to as many breakages.
Evacuated tube solar collectors are perfect for nearly any climate, but are more situated for northern climates with cooler temperatures, shorter days and lower sun angles Flat plate collectors, like PV panels, need to be placed directly facing true north, and at roughly the same angle as the location’s latitude. This means there are ar fewer options for the installation, and aesthetics must often be sacrificed in order to protect performance.
Evacuated tube solar collectors are often initially more expensive than flat plate solar collectors. But this investment can be recouped quickly, due to the increased performance of these collectors in a wider variety of climates and conditions. Flat plate collectors typically cost less from the outset than evacuated tubes.
Evacuated tubes capture sunlight better as they have a greater surface area exposed to sun at any time. Flat plate solar collectors can be used in most climates, but are significantly more effective in warmer, sunnier, southern climates, where freezing and solar angle are less likely to impact a solar water heating system.
Evacuated tubes require a smaller roof area than compared to flat plate collectors (typically you will find that for a flat plate collector area of 4m2, evacuated tubes need approximately 3m2 for the same size hot water tank.