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Renewable Energy Information for Everyone

Load Evaluation Form Instructions

If you have Adobe Acrobat Reader version 4.x, our load evaluation form will perform your calculations automatically. If you have Acrobat Reader version 3.x, or do not have the Acrobat plug-in at all, you can perform the worksheet calculations yourself.

If you own more than 26 appliances, you will need to fill the form out more than once, and add the Corrected Watt-Hours/Day and Total AC Connected Wattage At One Time from each form together to reach correct totals.

1. For each appliance you own, write in the appliance name, check the box for either AC or DC power (if you’re not sure, it is almost certainly an AC appliance), and write in how many of each appliance you own.

2. You then need to determine the Wattage of each appliance. Many appliances list their Wattage on a manufacturer’s label, however some appliances may only list their Amp rating.

If you have Acrobat Reader 4.x, the Wattage calculators on the right side of the form will automatically determine the appliance Watts. (Volts X Amps = Watts) Enter the Voltage in the designated box, and enter the Amps rating in the next box. (If you do not have Reader 4.x, multiply those two numbers and enter the results manually.) For DC appliances, enter the result into the Watts field in the middle section of the form.

For AC appliances, enter the Watts given into the second calculator, where it is multiplied by 1.15 to compensate for estimated inverter efficiency. (If you do not have Reader 4.x, you will have to multiply the figures yourself.) The number that results should be entered into the Watts field.

3. Estimate how many hours per day the appliance is used. A hair dryer may only be used for 10 minutes a day (0.1 hrs.), while a refrigerator will run up to 1/2 of the time (approx. 12 hrs.), and a digital clock will run 24 hrs. per day. Enter this number into Hrs./Day.

For users with Acrobat Reader 4.x, the form will perform the rest of the Watt-Hour Per Day calculations automatically. Skip to Step 7.

Users performing manual calculations should proceed to Step 4.

4. For each appliance listed, multiply Qty. by Watts. Multiply the result by Hrs./Day and enter the final figure into Avg. Watt Hrs. Per Day.

5. Add all Avg. Watt Hrs. Per Day together, and enter the result into the two bottom boxes labeled Total Watt-Hours Per Day.

6. Divide Total Watt-Hrs. Per Day by .70 (Load Correction Factor), to compensate for losses in the batteries, wiring, etc., and enter the result into Corrected Watt-Hours/Day.

7. Of the AC appliances listed, find the highest Wattage appliance, and enter its Wattage into Highest AC Load in Watts.

8. Determine how many AC appliances will be connected at one time. (If you own multiple power tools or kitchen appliances, but only use them one at a time, use the figure for the largest appliance in the group.) Add those wattages together, and enter the figure into Total AC Connected Wattage at One Time.

9. Print out the completed form, and save it for reference while sizing your alternative energy system components.