In a new report released by SolarCity, we are seeing that solar power systems have a usable lifetime of at least 35 years – 40% longer than the market expects. The key finding of the report is that power degradation (annual efficiency loss) of solar panels supplied to SolarCity is as much as 35% lower than for a comparable industry-wide selection of non-SolarCity panels, which are typically expected to last for 25 years. SolarCity feels it is the implementation of a stringent and industry-leading “Total Quality Program” that has driven this.

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SolarCity is in the unique position of being one of the largest deployers of solar panels – from multiple manufacturers – in the world, and with their tens of thousands of systems connected to a central database they know realtime performance. In the study here, SolarCity looked at greater than 11,000 panels to determine their data points and come to their conclusion that their solar panels are performing well beyond expected industry standards.

The key metric focused on is ‘degradation.’ Solar panels will lose a certain amount electricity production capability every year due to various effects –  water vapor inside the panels, sunlight slowly breaking down materials and the daily increase/decrease of temperatures. In order to make sure solar panels earn the money back for those who install them, solar panel manufacturers have been pushing their hardware quality. Today, standard efficiency solar panels put out by Tier 1 suppliers are generally warranted to lose no more than 0.7% efficiency per year for the first 25 years – this is the Power Production Warranty. SolarWorld proclaims to have offered the first 25 year power production warranty in 1997 – it has since become the industry standard.

The key finding in this study is that the annual 0.7% efficiency loss is too high an estimation – and that the number ought be closer to 0.5%. While it might seem a small number – a difference of 0.2% – when applied over a multiple decades timeframe, it means that instead of the standard twenty five year assumed productive life, we can expect at least another ten years of production above 80% of the original system output.


Premium solar panel manufacturer SunPower has been warranting their panels at 0.5% for several years already. A recent study has shown SunPower panels degrade at a rate lower than 0.25% per year. At the 0.25% degradation rate – SunPower has greater than 50 years before it’ll hit the 80% number. At the extreme upper edge of quality we have two Kyocera systems that produced for decades at their original production levels – no loss ever. SolarWorld offers a 30 year power production guarantee on certain products.

Current market pricing for a SunPower solar panel, in large volumes, is approximately $1.30/W, while a standard Tier 1 solar panel is priced at $0.65/W – 50% the cost.

What we are excitedly seeing is that the ‘economically priced’ products, coming from the largest manufacturers in the world, are increasing in quality and longevity, following pathways set by industry leaders like SunPower, Kyocera and SolarWorld. Large installers like SolarCity, able to do this type of widescale research – and to also demand higher quality, are showing their ability to pull the manufacturers of the world upward. With SolarCity building their own solar panel Gigafactory we ought expect the quality levels to be even greater in the near future. Is there an industry standard 50 year warranty coming?