Solar Module Efficiency

As manufacturers improve their processes, solar module efficiency increases.

But the real question is “Who cares?”.

A solar module’s efficiency is stated in a % (percentage) of how much energy is captured per square meter of solar panel. The module on the right is considered high efficiency with a rating of 20.2%.

Solar modules are tested (in a lab) at an irradiance of 1000 watts per square meter meaning a solar module that is one square meter in area would produce 1000 watts if it was 100% efficient.

If a solar module was one square meter in size and 50% efficient, it would produce 500 watts.

If it was one square meter and 75% efficient it would produce 750 watts.

The high efficiency Sanyo module in the photo on the right would produce 202 watts if it was one square meter in area.

The more efficient a solar panel is, the more power it can produce per square meter.


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Why pay more money per watt to save a couple of square feet on your roof’s surface? We wouldn’t!

So far solar modules are no where near 50% efficient. A high efficiency solar module is about 20% efficient while the norm is more like 12-17%.

Does this mean you should spend more money to get the 20% efficiency?

Not really unless you have a limited space to install the panels. The truth is a 100 watt solar module will produce up to 100 watts whether it is 12% or 20% efficient. The difference will be the size of the module.

Let’s look at a few modules:

Sharp ND-208U1F

Wattage: 208
Efficiency: 12.8%
Size: 64.6″ x 39.1″ / 1640 x 994mm

Sharp ND-240QCJ

Wattage: 240
Efficiency: 14.7%
Size: 64.6″ x 39.1″ / 1640 x 994mm

Sharp NU-Q250W2

Wattage: 250
Efficiency: 15.3%
Size: 64.6″ x 39.1″ / 1640 x 994mm

All of the above solar modules are exactly the same dimensions but as the efficiency increases so does the wattage. The above listed modules are listed in chronological order of when they were manufactured. As Sharp gets better at making modules, they can squeeze in more wattage in the same amount of real estate (square meters).

When looking for solar modules for your home or cottage, the efficiency is almost irrelevant. If you have lots of room for your modules, it makes sense to buy the modules with the best price per watt as long as they are of reasonable quality.

If you only have a small amount of space for your modules and need to get every watt possible, then it might make sense to buy a high efficient module.

Just remember a 240 watt solar module will make up to 240 watts!

A high efficiency 240 watt solar module will make the same 240 watts that the low efficiency module will make.

You will not get more power out of a high efficiency solar panel!

You will save a tiny bit of space but you will not see any difference in electrical output.

Where does efficiency make a difference?

Efficiency matters when purchasing an inverter, charge controller, batteries, wiring and any appliances. This higher the efficiency the better for all of the above mentioned devices.

Anything in your system that consumes energy should be a efficient as possible.

Check out the following articles to learn how to find the most efficient appliances…


Water Filtration

Circulating Pumps

Heating Systems


Gas Ranges


Why Do Solar Manufacturers Brag about Their Solar Modules’ Efficiency?

It has always been a battle between solar module designers to make the most efficient module but it is not for our benefit, it is for theirs and always has been.

Solar module’s are getting more efficient everyday.

If they can make a 200 watt solar panel in a 24 inch (60 cm) by 24 inch (60 cm) frame  or a 36 inch (90 cm) by 36 inch (90 cm) frame,which module will they make more money on?

The smaller one of course.

The smaller module uses less aluminum for the frame, less glass for the glazing, less silicon for the power generation, less caulking/glue…less everything.

Probably one of the biggest money savers with a smaller module are shipping costs. If the manufacturer can fit 1% more solar modules in a shipping container than their competitor it might make the difference between staying in business or going bankrupt.

Tagged as:
solar modules,
solar panels,
solar power