How much electricity can I get out of a kW?

Output of a system at any given moment depends on the amount of sun that hits the panels, the angle it hits the panels and the temperature. Shade will reduce output the most. In a system that does not experience much shade, and is oriented generally towards the south, you might expect about 1,050 kWhs out of every kW of a system in one year. If you want to estimate how big of a system you might need to make all your own electricity you can add up your total usage for a year, and divide by 1,050. So, for example, if you use 6,000 kWhs per year, you will need about 5.7 kW of solar panels to make all your electricity. If you have shade part of the day, or the orientation is significantly off of true south, you will likely need a bit more.

Interestingly the colder the panel is, the more efficient it is. And the more sunlight on the panel the more power that is made. So a cold sunny day with snow on the ground to reflect light at the panel can be great for generating power. The snow reflects the sun increasing the light that hits the panel and the panel is cold so the electrons can actually move more easily. But cold days are short days and so you still will make a whole lot more power in the long warm days of summer.