Solar panels have been popping up on roofs all over the country largely due to a period of government subsidies and favourable tariffs, coupled with the benefit of economies of scale and technology advancements decreasing panel costs.
If you have examined the return on investment you might be thinking that they look like a fairly good investment but how does the lifetime of the solar panels impact this investment?
Solar panels are still very much in their infancy and they have not been widely tested in practice yet for their whole lifetime so some assumptions have been made. Globally only a small proportion of solar panels have been installed for longer than 10 years.
Solar panel life expectancy
Most manufacturers give their panels warrantee guarantees of either 20 or 25 years. Warranties state that the panels will produce at least 80% of the initial peak output level for 20 or 25 years after the installation. Therefore the decrease in efficiency of the solar panels will be no more than 1% per year.
The Department of Energy and Climate Change have set the UK Feed-in-Tariffs at 25 years based on the assumption that the panels will last at least 25 years.
Research in Switzerland by the University of Applied Science of Southern Switzerland found encouraging results on the panels they tested. After 20 years a 10kW solar panel roof array was found to have only decreased in output by 11% from the initial peak output, which indicates a lower decline rate of 0.5%.
Solar panels can also suffer from some wear and tear such as the modules yellowing and laminate starting to peel off. Given that the panel is being exposed to the elements for 20 years, this is expected. This physical decay was found to only have minimal effect on their performance.
However, there are other parts of the system that should be considered. The inverters that convert the energy produced into useable energy only have warranties for 10-15 years and therefore a replacement inverter should be factored into the lifetime costs of your system.
Overall this picture is encouraging, as it offers guarantees on performance that balance the payback period given the length of time needed to get a return on the investment. More encouragingly some researchers have suggested that PV panels could effectively produce electricity for 40 years or more, although not at the initial peak rate but at an acceptable rate that would help yield a better return on the investment.
Do solar PV panels require maintenance?
Generally, the solar panels should be almost maintenance free but an annual or bi-annual clean is advisable to ensure the maximum output is achieved. Some physical decay is expected but you should reduce potential risks where possible like from falling objects such as branches.
It is also advisable to frequently monitor the performance from the panels to detect any decreased output or anomalies so it can be investigated and reduce the time that performance is lost. Apart from this the only time a trained professional would be needed is to exchange the inverter when that stops working.