The solar heat gain is close to 1kw per square meter. The wood stove that heats half of our house is only 6kw.
Where, for how long and when? Certainly not when you need to regularly use a wood stove for heating, at least not around here in northern Europe. :)
I'm not sure where I read 1000W but it is for a square meter perpendicular to the sun's angle. Here in North East USA, solar installation folks say we get "3 hours" of direct sunlight per day in winter and 6 hours in the summer. I think that accounts for shorter days and weather.