Solar panels typically last for about 25 to 30 years and the efficiency is reduced over a period of time. However, they do not stop working at the end of the so-called lifespan; they only slowly degrade and the energy production gets reduced by what manufacturers consider to be a significant amount. One of the main reasons why solar panels have such a long lifespan is because they do not have any moving parts. As long as they are not physically damaged by any external factors, solar panels can continue work for decades. Solar panel degradation rate also depends on the panel brand and as solar panel technology gets better over the years, the degradation rates are improving.
Statistically, lifespan of a solar panel is a measure of percentage of power generated over years against the rated power of the solar panel. Manufacturers producing solar panels calculate around 0.8% efficiency loss per year. Solar panels are expected to produce at least 80% of the rated power to work efficiently. For example, for a 100 Watt solar panel to work efficiently, it needs to generate at least 80 Watt. To know how your solar panel will perform after a certain number of years, we need to know the degradation rate of the solar panel. On average the rate of degradation is 1% each year.
Energy payback time (EPBT) is the amount of time for a solar panel to produce enough energy to pay back the energy used to manufacture the panel and a solar panel lifespan is usually longer than its EPBT. A well-maintained solar panel can lead to a lower degradation rate and also better panel efficiency. Solar panel degradation can be caused by thermal stress and mechanical influences impacting the components of the solar panels. Regularly getting the panels checked can reveal issues like exposed wires and other areas of concern to ensure the solar panels last a longer period of time. Clearing the panels off debris, dust, water seepage and snow can increase the efficiency of the solar panels. Blocking of sunlight and scratches or any other damages on the panel can affect the performance of the panels. Degradation rate is relatively very low in a moderate climatic condition such as in India.
The performance of a solar street light majorly depends on the efficiency of the solar panel it uses. With more and more individuals and businesses investing in solar energy, it is only natural to expect the most important and the most expensive component of a solar street light unit to be durable and worth the money. The most common solar panels used now are monocrystalline and polycrystalline solar panels, both of which have almost similar lifespan. Nevertheless, degradation rate of polycrystalline solar panels is slightly higher than monocrystalline solar panels. If the panels are not broken and if they are producing sufficient electricity for your needs, there is no need to replace the solar panels even after their warranty time.