Off Grid Load Worksheet

FAQS Content:

WORKSHEET OFF-GRID LOAD

Worksheet Off-Grid Load: Determine the total amp-hours per day used by the AC and DC loads.

________ Step 1: List all AC loads, wattage and hours of use per week in the table below. (If there are no AC loads, skip to Step 5)
Multiply watts by hours/week to get AC watt-hours per week (Wh/Wk). Add up all the watt hours per week to determine total AC watt-hours per week.

NOTE: Wattage of appliances can usually be determined from tags on the back of the appliance or from the owner’s manual. If an appliance is rated in amps, multiply amps by operating voltage (120 or 240 VAC) to find watts.

Calculate AC loads (If there are no AC loads, skip to Step 5)

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________ Step 2: Convert to DC watt-hours per week by multiplying the result of Step 1 by 1.5 to correct for inverter loss.

________ Step 3: List the inverter DC input voltage. Usually 12, 24, or 48 VDC. This is DC system voltage.

________ Step 4: DIvide the DC Watt-hours per week by the DC system voltage to get the total DC amp-hours per week used by the AC loads.

________ Step 5: List all DC loads, wattage and hours of use per week in the table below. Multiply watts by hour/week to get DC watt-hours per week (Wh/Wk). Add up all the watt hours per week to determine total DC watt-hours per week.

Calculate DC loads (if applicable)

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________ Step 6: List DC system voltage. Usually 12, 24 or 48 VDC.

________ Step 7: Divide the total watt-hours per week by the DC system voltage to find total amp-hours per week used by the DC loads.

________ Step 8: Add the total DC amp-hours per week used by AC loads from Step 4 to the amp-hours used by DC loads from Step 7 to get the total DC amp-hours per week used by all loads.

________ Step 9: Calculate your amp-hours per day. Divide the total DC amp-hours per week from Step 8 by 7 days to get the total average amp-hours per day that needs to be supplied by the battery.

You will need this number to begin sizing the PV array and Battery Bank. Note that the Solar Array Sizing Worksheet in this section, as well as the Battery Sizing Worksheet in the Batteries Section, both begin with this number in their Step 1.