How do you know how much money you'll save?
Collecting Solar Energy is just like collecting Rainwater.
If you multiply the size of the bucket by how frequently it rains you can determine how many gallons you can expect to capture a year.
Bucket Size (5 Gallon) X Annual Rainfall (25 Gallons) = 125 Gallons
Then multiply this by the amount you pay for a gallon of water to determine your savings.
125 Gallons X Cost of a Gallon ($ 1.50) = You Saved $ 187.50
Collecting Solar Energy
If you multiply the size of the Array by how frequently the sun shines you can determine how much energy you can expect to capture a year.
Array Size (4.2 kW) X Annual Solar (1,464 kWh = 6,149 kWh
Then multiply this by the amount you pay for a kWh of electricity to determine your savings.
6,149 kWh X Cost you pay per kWh ($ .1135) = You Saved $ 698
For accurate collecting capacity calculations, always reduce the Nameplate Array Size (In this example 4.2kW) by 22%. Panels on a roof get hot and so are less efficient (-9%), converting Direct Current to Alternating Current and a few other factors (-13%) are what accounts for this 22% reduction.