There is a common but wrong idea that solar panels are only effective in places with a lot of sunshine. The reality is that home solar panels are being used successfully in less sunny regions like the US Northeast and Pacific Northwest.
You can also find examples in other parts of the world: Netherlands and other nations have more than 600 watts of solar capacity per person, according to a recent report by SolarPower Europe (PDF). Those nations have relatively low sunshine.
Abundant sunlight makes solar panels more productive, which means they produce more kilowatt-hours per year. But, you also need to consider local electricity prices, since they determine the dollar value of those kilowatt-hours!