Use this worksheet to determine the total amp hours per day used by all the AC and DC loads in your system
Calculate your AC loads
If there are no AC loads, skip to Step 5
1. List all AC loads, wattage and hours of use per week.
Multiply watts by hours/week to get watt-hours per week (WH/WK.).
Add up all the watt hours per week to determine AC watt-hours per week.
Note: Wattage of appliances can usually be determined from tags on the back of the appliance or from the appliance owner’s manual.
If an appliance is rated in amps, multiply amps by operating voltage (120 or 240) to find watts.
2. Convert to DC watt-hours per week by multiplying line 1 by 1.15 to correct for inverter loss.
3. Take the inverter DC input voltage (usually 12-, 24- or 48 volts). This is DC system voltage.
4. Divide line 2 by line 3. This is total DC amp-hours per week used by AC loads.
Calculate your DC loads
5. List all DC loads, wattage and hours of use per week.
Multiply watts by hours/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.
6. DC system Voltage. Usually 12, 24, or 48 volts.
7. Find total amp-hours per week used by DC loads; divide total in line 5 by line 6.
8. Enter total DC amp-hours per week used by AC loads from line 4.
9. Add lines 7 and 8. This is total DC amp-hours per week used by all the loads.
Calculate your amp-hours per day
10. Divide line 9 by 7 days. This is total average amp-hours per day that needs to be supplied by the battery. Remember this number when sizing batteries.
