Give me that sun: Efficiency and world’s most efficient solar panels in 2022
- 01 Aug 2022
- 11 min
Top-5 most efficient solar panels: comparison table
Efficiency doesn’t always mean high costs. While solar panels by Sunpower, LG, Panasonic and REC are rather costly, Canadian Solar offers relatively inexpensive PV modules. They come at $0.6–$0.9 per Watt.
Solar panel efficiency shows how much sunlight it turns to DC
You might wonder: why don’t solar panels turn all of the sunlight into electricity? The modules actually can’t make use of certain wavelengths of solar radiation. Besides, the conversion process itself is not perfect and lots of energy gets lost. The solar industry has come a long way though: first silicon panels that appeared in 1954 had only a 6% conversion rate!
Efficiency depends on how modern the solar panel is
The type of panel that you use plays a major part. Today monocrystalline panels are the most efficient and the majority of solar brands don’t even make anything else. Manufacturers like Canadian Solar still toy around with polycrystalline panels, but their conversion rates aren't nearly high enough: around 14–17%. Thin-film panels were by default the least efficient type of panels out of three, but they are still being developed, modernized and have a bright future.
Several technologies serve to maximize the energy conversion rate of a module as well.
PERCs or Passivated Emitter Rear Cells. Each cell is manufactured in such a way that it can reflect the sunlight in itself and use it again. PERCs modules’ efficiency is 1% higher than that of standard solar panels.
Most brands are fine with using only a few of these innovations in their modules. Implementing all of them at once drives the manufacturing expenses way up. So while LG and Sunpower did win in our solar panel efficiency comparison table, the cost of this victory is high.
External factors affect the efficiency as well
Location and sun hours. Some areas just have more sunlight throughout the day than others, therefore the irradiance of panels in these sunny places is higher on average. Even if your panels aren’t all that efficient, they will harvest more solar energy in Los Angeles than our Top-5 modules would do somewhere in Alaska.
Let’s set an example. The Aptos Solar 365 W panel has a temperature coefficient of −0.36%/°C. The solar panel’s temperature is always higher than the air ambient temperature. On a sunny day Aptos module heats up to 44 °C, which is marked as Nominal Operating Cell Temperature (NOCT) in the datasheet. Let’s see how much output it provides in these circumstances:
365 W − (44 °C − 25 °C) × (365 W / 100 x 0.36%) = 365 W − 24.89 W ≈ 340 W
REC and Panasonic engineers use heterojunction cell technology that gives their panels lower temperature coefficients — around −0.25%/°C.
Time of year. This one is pretty straightforward — there is just less sunlight in the winter and fall compared to spring and summer. The irradiance falls and so does the efficiency. In June-July panels generate about 50% more energy than in December-January.
Calculating the efficiency of a Q CELLS panel
Efficiency = [Power output / (Area of panel x solar irradiance)] x 100%
Power output can be easily found in the solar panel spec sheet. Area of panel means the whole area of a panel, not just its active surface. In the past there were brands that increased the efficiency numbers of their panels on paper by not including the frame in calculations (not fair!). Standard solar irradiance in lab conditions is 1000 W/m² which is roughly equivalent to a sunny day.
Let’s do the math ourselves. Imagine we have a Q CELLS Q.PEAK DUO G6+ panel which gives 350W output and is 68.5 x 40.5 inches in size (or 1740 × 1030 mm). Therefore the area of a panel is 1.7922 m². Let’s calculate the efficiency:
[350W / (1.7922m² x 1000W/m²)] x 100% = 19.52%
Did we do it right? According to the datasheet, the efficiency of a 350W module is indeed equal or greater than 19.5%.
Efficiency is a good but not the most important metric
But what if we have two panels of the same power output but with slightly different efficiencies? Well, they are going to provide just the same amount of energy, but the more efficient panel is going to be slightly smaller.
If space is not a constraint for you, then efficiency is not the most important metric to look out for. Keep in mind, however, that a typical residential system consists of 15–35 panels: the bigger the system, the more significant the panel size becomes. Having efficient panels is especially important in a mobile installation. On a boat or on an RV, you might have room for only a couple of modules.
Here’s the bottom line: while it’s easy to compare solar panels efficiency, by itself it becomes a deciding factor only in specific situations, such as high energy needs combined with lack of space. Otherwise, we suggest paying more attention to power output of a panel, price and warranties.
Learn about the latest arrivals and discounts first!