Solar Energy

Solar Energy Worksheet
Use this worksheet as if you will produce 100% of your electrical needs, then scale back to fit your budget. You will ultimately need to decide if you are going to have an independent/stand alone system which produces 100% of your power or a grid-inter-tied system which allows you to buy part of your electricity from the grid.

1. Calculate the daily output needed from your PV system:

Average Monthly Electricity Use _________KWH
(Add the monthly totals for several bills and divide by the number of bills.)
x 1,000 (converts KWH to Watt-Hours) = __________WH
X _____%* of Monthly Electrical Use from PVs = __________WH
divided by 30 days
= Daily PV Output Needed __________WH

2. Calculate the minimum system size of the "solar array" or group of solar panels you will need (in watts):

Daily PV Output Needed (from Step 1) __________WH
Divided by Average Peak Sun Hours (_____ hrs) Per Day =__________W
divided by 0.7 or .85 for System Efficiency Factor
(.7 for independent system with batteries or .85 for more efficient grid-tied system)
= Minimum System Size __________W

3. Determine the number of PV modules you'll need:

Minimum System Size (from Step 2) __________W
divided by Wattage Rating (_______ W) of Chosen Module
= Number of Modules Required _______Modules

4. Find the size of the system (how many watts per hour your array should produce):

Number of Modules Required (from Step 3; round up) ______Modules
x Wattage Rating (_______W) of Chosen Module (also from Step 3)
= System Size (in Watts) __________W

Calculation worksheet is a modified version of the original published by Home Power Magazine, www.homepower.com