Solar panel efficiency is not important – SolarWisely


Solar panel efficiency – Does it matter?

You’ve heard it many times: Solar panel efficiency.

It sounds so simple….

Is it the efficiency that you should all care about? That’s the focus in this post…

A lot of you may be searching the internet for solar panels with the best efficiency. It is not your fault. The solar companies might be to blame. That’s how they like to advertise their product: “our solar panels are more efficient, hence produce more power.”

While it is true that some solar panels are more efficient than others, what I am about to tell you today might change your perception for good: Solar panel efficiency doesn’t really matter.

So, take a deep breathe and smile. You may agree with me by the time you finish reading this post.

But, first….

What is solar panel efficiency?

It’s the sunlight to electricity conversion ratio from a certain area.

You may have come across something called solar ‘cell’ efficiency as well. It is important that you understand the difference between solar panel and solar cell efficiency. Allow me to explain…

Solar cell efficiency

Every so often you hear about this in a headline, ‘New record for solar cell efficiency’. The latest one was just in May 2016, from UNSW (Yes, in Australia). Here is the news link. 

Source: UNSW Newsroom

Researchers in U of NSW were able to set a new world record, which was considered a quantum leap, for silicon based solar cell (silicon is the most commonly used material in solar panel). Sunlight to electricity conversion ratio of the new silicon cell was 34.5%. 

However, these R&D solar cells are only prototypes. They are long ways from mass production. And, there is good chance we may never see them in commercial application.

Solar panel efficiency

You don’t hear a lot about record-breaking solar panel efficiency in the news. To be honest, it is not as dazzling as the solar cell efficiency. But it is quite often used by the marketers.


Solar panels, or solar modules, are made of 50-100 solar cells depending on the size of the panel. The combined output is the module/panel efficiency.

Solar panel manufacturers are slow to adopt the more efficient cell technology in mass production because that would significantly increase their manufacturing cost, and eventually increase the price of solar panels. That’s going in the wrong direction for price.

Thus, commercially viable solar panel efficiency has only marginally improved over the last decade.

How is solar panel efficiency calculated?

When 1000 watts of sunlight clashes a solar panel, if 200 watts of electricity is generated, that’s 20% panel efficiency.

The output of a solar panel is maximum when,

  • Solar panels are facing North (or, South in Northern Hemisphere)
  • Solar panel is inclined at the same angle as latitude (37° in Melbourne).
  • Surface temperature is maintained at 25°C.

Every manufacturer is required to calculate its panel’s efficiency under these standard test conditions (STC). The efficiency that is published is the maximum efficiency.

Most efficient solar panels

If you hadn’t heard, a US based solar company named SunPower makes the most efficient solar panels in the whole world. Their X-series residential solar panels leave the competitors in dust: top panel efficiency is 22.2%. That means, this solar panel would produce 222.22 watts of solar electricity from 1000 watts of sunlight under STC conditions.


SunPower uses high quality silicon that yields better cell efficiency. SunPower also invests heavily to improve the efficiency of its panel by improving; surface heat dissipation mechanism, power loss in circuitry that connect the cells, etc. The combined output is breathtaking. Downside? It comes with price.

Based on popularity, there are mainly three types of solar panel available in the market: Monocrystalline, Polycrystalline, and Thin-film. All high efficiency solar panels, such as SunPower X-series, are made of monocrystalline silicon.

Majority, though, are made from polycrystalline silicon, and their efficiency ranges between 15-18%. If you want to read more on the three types of panels, check out my other blog post: Types of Solar panels

Roof space vs. solar efficiency; how are they related?

This is where it gets interesting..

As long as you have plenty of roof space, efficiency of solar panel doesn’t matter so much. Let me explain…

Let’s say you want to produce 10kWh of solar energy everyday for your home. In Melbourne, this would require 3 kW (or 3000 watts) of solar panels.

If you are not so sure about kWh and kW, jump to kW and kWh explained with examples

You have two options:

  1. Buy 10 of the SunPower solar panels @300 watts/panel, or,
  2. Buy 12 solar panels, from Jinko solar, @250 watts/panel (sunlight to electricity conversion is lower, hence only 250 watts/panel)

Both options, #1 and #2, will produce 3000 watts. But, if your roof space is not premium, meaning you have plenty of roof space, adding 2 extra panels to make up for the efficiency, is going to save you money. 

Efficiency vs. Performance & reliability

Both, performance and reliability, of a solar panel has nothing to do with its efficiency, and everything to do with its manufacturing standards.

One company which is well known for making highly efficient panels that also perform better and last longer, is SunPower. The only downside is the heavy price tag, 20-40% higher than standard panels. For example, if 1 kilowatt of standard polycrystalline panels cost $1600, the same size of SunPower panels can cost up to $2200.

If you have the money and the desire, SunPower solar panels offer a complete package of efficiency, performance, and reliability. Otherwise, worry less about the efficiency, and invest more on performance and reliability.

Are less efficient solar panels a better deal?

Maybe, but efficiency is a wrong metric to go after. Because, the best value solar panels really has nothing to do with efficiency.

Value of solar panel should be determined by the cost of electricity it produces. If adding two panels is cheaper than paying premium for better efficiency, that’s a better value.

Instead…. focus on the brand/manufacturer, performance, and warranty aspects of the panel. I know there is plethora of panels to go after. So, the best would be to get few quotes from solar companies, and then ask the questions you have in mind about the solar panels thats in the quote.

What all of this means is: Solar panel efficiency should be the least of your concern. Avoid products that are towards the bottom end of the price as well as efficiency (that’s a bad combination). Find a middle ground for price, performance and reliability. And the main takeaway is, do not pay premium for solar panels because the efficiency is high. 

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