Once you've decided to add a system of solar photovoltaic power panels to your house or business or determined that it's time to expand an existing system, the next question is: how much wattage do I need?
To find this out, you will need to know how much power you consume (or how much you plan to consume, for new buildings or for additions that will require lots of power – like a woodworking shop or a hot tub) and how much sunlight you receive throughout the year.