Pictures are worth a thousand words right? I still have customers who don’t believe washing coils is important. Now whenever I have this issue come up I’ll send these pictures. This unit was drawing 15% more amps before washing, the supply air temperature was 64 instead of 58, and the compressor was overheating. Remember, dirty units = increased energy costs, decreased cooling performance, and more frequent repairs. Even when the coils are not this dramatic the technician can see results from washing coils. A coil can look clean but have dirt deep inside it. The technician can tell based on refrigerant pressures and the amperage of motors. So don’t always count on such dramatic pictures but do trust your technician when they tell you the coils need to be cleaned. They are trying to save you money.