To clean siding with an electric pressure washer, start by selecting the appropriate nozzle tip for the task. A 25- to 40-degree tip is usually recommended for cleaning siding. Next, connect a garden hose to the pressure washer and plug it into a power outlet.Before you begin washing, it's important to protect any nearby plants or landscaping with a tarp or plastic sheeting. Then, start spraying the siding from the top down, working in small sections to ensure thorough cleaning.