Due to their wide availability, flat plate collectors are less expensive than ET collectors, an important consideration in any solar collector comparison. In addition, flat plate collectors are less vulnerable to damage than ET solar collectors, making it less likely that any given flat plate unit will be harmed by debris or mishap. In addition, the flat plate panel radiates more heat back into the exterior, which allows it to effectively melt snow or ice that may accumulate on the panel in cold climates. On the other hand, these heat losses are responsible for a lower efficiency for a flat plate collector than an evacuated tube collector.
Other potential downsides to flat plate units are that they can be more difficult to install given their size and weight, and they are also more sensitive to the angle of light hitting them. For some houses, this will require more extensive and expensive roof modifications in order to allow for an effective installation. Those making a solar collector comparison should also consider that if a flat plate solar panel is damaged, the entire panel must be repaired or replaced.
Image: Willemferguson, via Wikimedia Commons
The Evacuated Tube Collector
Evacuated tube collectors are a more recent innovation and have a number of advantages. The first is the fact that each tube can be installed individually and ET units are less sensitive to the angle of sunlight, making installation and repair somewhat easier. In terms of a solar collector comparison, this allows a more effective installation on homes with irregular roofs than the flat plate design.
In addition, ET panels operate at higher temperatures, making them superior for use if higher temperatures are needed (i.e. space heating, industrial process heating, high demand). An ET collector also delivers more heat under cloudy conditions when solar insulation is at a minimum.
The vacuum keeps heat losses at a minimum, and an ET collector generally supplies much more heat than a flat plate collector. For homes located in mild-to-cold climates, an effective solar collector comparison would likely support installation of an ET panel.
In either case, the homeowner should consult with experienced solar professionals when making a final solar collector comparison.