Links for more information:
How long do they last?
Studies for 40 years on about 2000 different solar setups show the average degradation rate for panels has been about one half of one percent per year (.5 %). Panels still show about 88% production after 25 years. Click here for the study.
Cleaning
Solar panels require frequent cleaning, as often as every week or two. It helps to have a self-cleaning surface on the glass. The surface allows you to rinse off the glass, rather than having to wash and squeegee. The following short video shows one solution to treating the glass. There are surface treatments available today that may assist. Be careful that the treatment does not degrade the solar power accumulation of the panel. In any case, keep the panels clean, especially through the summer months when there is little rain.
Here is a good example of what the effects of cleaning the solar panels can look like. With a 30 panel array of 405 w panels, the expected improvement is about 1 Megawatt per year. Panels should be cleaned each month in the Summer months if you live in an area of dusty air. These are cleaned with a long water brush with a water filter to filter out the calcium to avoid water stains from repeated washings over the years. On the left 5 days, one slightly cloudy, you can see the average sunny day is about 79 kWh production in May. However, the total jumps up to 84 kWh after cleaning.
