You can go hunt down a power washer or you can get in touch with your inner alchemist.
How to clean vinyl siding without a pressure washer.
Cleaning your siding by hand or with an outdoor cleaning wand has the added benefit of greater precision and is better for many types of siding.
How to wash your house.
If your white siding is beginning to look a little green then this is the route you want to go as it is very powerful against mildew and mold.
If mildew is present use a solution of 1 quart of bleach to gallon of water and a small amount of the tsp detergent.
When the vinyl siding on your house starts getting all gross and mucky there are a few ways to deal with it.
If you just moved or have lost your power washer you may want to clean your siding without a power washer.