Cleaning solar panels every month or few months can generate 15-20% more energy and shave 3-5 years off the payback period of a solar installation. Not cleaning a 3kw system can lose around 2.7 kWh per day or 985 kWh over a year, equal to losing a full hour of generation time daily. Basic cleaning with a vinegar and soap solution using a long-handled squeegee tool makes it safe and efficient to clean panels.