Pricing for power washing jobs has many variables. Because there are so many differences from job to job, there is no way to accurately set prices. Some factors to consider are square footage and level of dirt. If the moss or algae infestation is serious, it may need multiple soft wash treatments to properly remove the infestation. Surfaces may need spot treatments for grease or rust before surface cleaning. To restore some structures, a combination of soft washing and pressure washing will need to be applied. Fees for cleaning solutions vary depending on severity of dirty surfaces. The steepness of your roof may require more or less cleaning solution. You may only be interested in cleaning the north facing side of your roof. Combining services will also lower pricing. Some jobs are completed using hourly rates and others are bid by type and size.