Let’s start with a simple question? How much of your electricity usage do you want to offset with solar? If your household uses 14,000-17,000 kWh per year and you wish to offset it all with solar, let’s see how much solar that is. You can get your exact usage with a copy of your current electric bill. We’ll take the high end of 17k for this exercise.
17,000 kWh annually / 365 = 46.57 kWh used daily on average. Figure 4 hours of sun, so now we need a system that produces a rounded up figure of 12kW. (12kW x 4 hours of sun = 48kWh)
40 panels at 365 watts per would yield a system with a label rating of 14.6kW. Let’s take off that 20% that you lose in the DC to AC inversion process here. The labelled 14.6kW system will produce around 11.7kW. If we see just 4 hours of good sun per day, this system will produce an average of 46.8kWh daily and is capable of producing 60+kWh on a good day.
So if you use 17,000 kWh per year, a system with 40 x 365 watt panels will give you 100% offset. This will just cover your needs. If you expect a rise in usage over the years, maybe add a few panels on the front end… or even add them later.
If you wish to cover only half of your electric usage with solar, or if your usage is higher or lower, these numbers can be extrapolated to suit your situation. It all starts with an accurate count of your last 12 months electrical usage and a realistic expectation of what your panels will produce.
So… you came to determine your needs. You want to go full offset and we’ve figured that out.