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In it's favor, a solar power satellite can get light nearly 100% of the time, while on the ground you are luck to average 50% with rotation and weather.

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In what orbit, that doesn't require propulsion, do you get constant line of sight?

They nearly always call for geosynchronous orbit, because they want to always be over the rectenna on the ground.

The Earth will occasionally put such a satellite into shadow, but remember that the Earth is tilted, and so is the equator.

Getting up to GEO is hella expensive.

Just to put some numbers on it, GEO doesn't intersect the Sun-Earth line most of the time. The Earth's shadow touches GEO for a couple of weeks around the equinoxes, resulting in up to 70 minutes of shadow per day in that period. The rest of the time, they're in sun 100% of the time. So, as low as a 95% duty cycle at the worst point in the year, and 100% for most of the year.

L1

reference: http://en.wikipedia.org/wiki/Lagrangian_point#L1

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