When choosing panels for your solar power system, there are a number of factors worth considering.
The cost of a solar panel is determined in part by the size (in Watts), the physical size, the brand, the durability / longevity (or warranty period) and any certifications the solar panel might have. Choosing a solar panel on price alone is not wise, as it may not fit the area you wish to install it, may not have the necessary certifications to qualify for government rebates, or may not have the warranty required for economic payback of the power produced.
Durability / Longevity / Warranty
The durability or longevity of a solar panel is important for a number of reasons. Firstly, if the solar panel only has a 10 year warranty and it is used in a grid connect system you would expect the solar panel to produce enough power to pay for itself within 10 years.
Also, if the panel is to be used in a critical system you shouldn’t risk installing solar panels that aren’t as robust as the others. Reputable solar panels will have warranty a period of 25 years.
Solar Panel Size and Wattage
The size of the solar panel in Watts will directly affect the price, as solar panels are usually priced (and compared) in dollars per Watt.
Watts are related to the output of each panel; meaning a 100 Watt panel under ideal conditions will generate 100 Watts of electricity each hour and a 200 Watt panel will generate 200 Watts each hour. Therefore expect to pay double price for the 200 Watt panel, compared to the 100 Watt panel.
The output of a panel also affects the physical size of the panel, meaning the 200Watt panel will be larger in size to the 100 Watt panel.
The type of solar cells used in its production also determines the size of the solar panel. They key issue to consider is that your system overall has enough Watts to power your appliances, and that the solar panels will physically fit in the area you wish to install them.
Solar Panel Efficiency
There’s much debate about efficiency in solar panels, i.e. how effective the panel is in converting sunlight to electricity; but the key point to remember is that a 100 watt solar panel will produce 100 watts; regardless of its efficiency ratings.
Solar Cell Type
There are 3 main types of solar cells.
The most efficient and produces the smallest solar cells, and therefore the smallest panels.
Poly-crystalline (or multi-crystalline) silicon
Produces the next most efficient type of cells, but equivalent wattage panels are larger than their monocrystalline counterparts
Amorphous (or thin-film) silicon
Uses the least amount of silicon and also produces the least efficient solar cells. This means thin film system take up more area than the other two, but it has the advantage of offering flexible panels that can be used on curved or irregular surfaces not suited to solid panels.
Solar Panel Suitability
Mono-crystalline and multi-crystalline work very well in bright cool conditions, whereas amorphous (thin-film) silicon will be more efficient at higher temperatures.
We generally recommend monocrystalline or multi-crystalline for large unshaded roofs, and amorphous panels for roofs with partial shading.
Regardless of the technology currently in use, a solar panel in full shade will only generate a small fraction of its rated capacity; so the “shade tolerant” features you may see advertised can be somewhat misleading.