Don't be too sad in Seattle. It turns out Seattle WA has about 70% as much sunshine as California. This means that a solar electric system would still work very well in your climate, it just needs to be larger to get more power than if you lived in a sunnier state. The same is true for Michigan and New York, for example. Less sunshine, but a larger solar electric system can still meet your electricity needs.

Solar Mike

Seattle of course has those stratus clouds that cover everything, and drizzle down on you poor seattle-citizens. Hence the coffee! ;-)

Go someplace where there are scattered cumulus clouds, and you may get more solar energy on head or your rooftop than on a clear day! That's because you not only get the direct rays of light from the Sun, but also sunlight reflecting towards you off the sides of the cumulus clouds. The upper limit of this effect can be quite large – in fact the cloud-reflected solar energy can be as large as the direct, so can double the sunlight you'd get on a clear day. Usually, though, it is more like a 30% enhancement when scattered cumulus clouds are in the sky.

You can still use solar thermal (e.g., a solar hot water heater) on cloudy and rainy days, but it won't be nearly as efficient as on sunny days. You will still produce some warm water, but don't do all your laundry on those days! If a house is designed properly (called passive solar design), even if the house is located in an area with lots of clouds and rain, it should stay pretty comfortable.