Solar Electric System Sizing
Step 1 - Determine Your Power Consumption Demands
Make a list of the appliances and/or loads you are going to run from your PV system. Find out how much power each item consumes while operating. Most appliances have a label on the back which lists the wattage. Specification sheets, local appliance dealers, and the product manufacturers are other sources of information. We have provided a chart that lists typical power consumption demands of common devices which you can use as a guide. Once you have the wattage ratings, fill out the load sizing worksheet.
• List all of the electrical appliances to be powered by the PV system. • Separate AC & DC devices and enter them in the appropriate table. • Record the operating wattage* of each item. • Specify the number of hours per day each item will be used. • Multiply the first 3 columns to determine watt-hour usage per day. • Enter the number of days per week you will be using each item to determine the total watt-hours per week each appliance will require.
* Most appliances have a label on the back that lists the wattage. Local appliance dealers and the product manufacturers are other sources of this information.
• Load Sizing Worksheet
DC Appliance
Watts x Qty x Hrs/Day
= Wh/Day x Days/Wk
= Wh/Wk
A___________
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B___________
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C___________
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D___________
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E___________
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Total the numbers in the last column. This is your DC power requirement.
TOTAL ______
Multiply the total by 1.2 to compensate for system losses during battery charge/discharge cycle.
DC WH/WK ______
1.
Add AC WH/WK and DC WH/WK together. This is your total power requirement per week.
TOTAL ______
2. Enter the voltage of your battery bank (usually 12 or 24 volts).
VOLTS ______
3. Divide line 1 by line 2. This is your amp-hour requirement per week.
AH/WK ______
4. Divide line 3 by 7 days. This is your average amp-hour requirement per day that will be used to size your battery bank and your PV module array.
