Efficiency of solar panels and what impacts performance

Understanding the efficiency and performance of solar panels is key in understanding whether they’re a good investment for you. Here’s what you need to know in 5 minutes or less!

How efficient are solar panels and how will that change over time?

Different solar panels will have different efficiencies, but the technology is in a fairly mature place and we're seeing panels consistently producing good amounts of power for 25+ years. Over this time and beyond, the performance will deteriorate and this will vary depending on the panels that you get. Some solar panels have a performance guarantee, such as “95% for the first 5 years and 80% for the first 20 years”. What this means is that in the first 5 years of the life of the panel, it will perform better than 95% of its maximum capacity, and within the first 20 years, it will perform at above 80% of its peak.

Check with your Green Homes Guru about different panels’ performance over time and look for charts like the one below to quickly get an understanding of how they will perform. Don’t yet have a Guru to ask? Book a free call by going through the MakeMyHouseGreen platform here.

What this means is that for the example guarantee described above, at year 20 in the life of a 330W panel, it will actually have a peak performance of 264W (80% of 330W). So, if you have a system with 12 of these panels (12x330W = 4.0kW) it will still be producing power like a 3.2kW system (80% of 4.0kW) after 20 years.

There are panels with higher performance guarantees, up to around 90% at 25 years, but these are more expensive. For comparison, this higher quality panel will be producing power at ~93% of its original capacity at the equivalent 20-year mark. That is, the 4.0kW system will now be producing power like a 3.6kW system. You will need to consider whether this additional performance, and associated cost, is something that you are interested in.

What impacts the efficiency of solar panels?

The efficiency of your solar panels is dependent on whether they’re mono-crystalline or poly-crystalline panels, but more importantly, on the direction they’re facing, where you are geographically in the country, and what the weather is like, etc… It all comes into it!

For example, imagine you had a house that had 10 panels facing due south, and 10 panels facing due north. The panels facing south could be generating 4025kWh per year, while the ones facing north could be generating only 1664kWh per year, the difference being the direction they’re facing. If you were to imaginatively move the house to another part of the country, these numbers would change despite the directions staying the same!

Shading from neighbouring properties, chimneys, and trees, to name a few things, could have an impact on the solar panels’ efficiency as well.

Now that you're an expert in the efficiency of solar panels, you should be in a much better position to make the right choice for your system. We cover more about other system aspects in other articles, but if you have any questions in the meantime, check out our FAQ Page or drop us an email via team@makemyhousegreen.com.

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