Yes! Solar power works in the Northwest!

Athough higher latitudes receive fewer annual hours of sunlight, solar panels operate at greater efficiency in cooler climates making the Northwest an excellent place for solar. Germany, which has latitudes equal to Seattle in its south and the southern tip of Alaska in its north, has 55% of the world's solar panels and is expecting to be %100 green in its national energy use by 2010.

This link talks about Washington state's solar potential :
http://www.rnp.org/RenewTech/tech_solar.html

The best part is that Washington and Oregon have some of the best incentive programs in the country. These incentives make solar more financially beneficial than in the majority of the southern states.