Electrical Load Calculation and Usage Forms (Click here to return to Homeowners)

It is recommended that a load analysis calculation be performed to validate the assumption that approximately 50% of your electrical loads can be powered by the PV system. Solar PV will never power electric water heaters, electric clothes dryers, baseboard heating, electric stoves, and air conditioners because these devices use too much electricity. Do NOT include these electrical heating and cooling appliances in your calculations. For energy conservation one should attempt to replace these appliances with non-electrical equivalents such as natural gas or propane versions.

The analysis is to calculate the total electrical usage for a typical summer day and then repeat the calculation for a typical winter day. In these calculations you will multiply the size of each electrical load in your house times the number of hours that it is on per day, for example, a 100 watt light bulb that is on one hour in the AM and 5 hours in PM, is on for 6 hours and represents 600 watt-hours. This calculation is performed for all loads and will result in a figure that can be compared with your utility bills, to make sure that this "ballpark" calculation is close to the actual usage. You may expect to have a figure such as 30 to 40 kilo-watt-hours per day.

Step 1: Download Electrical Load Spreadsheet and make 2 copies, labelling them Summer and Winter.

Step 2: identify all of the electric loads in your house and write them down in both Electrical Load Spreadsheets

Download the Appliance Energy Table with their wattage rating. The table also contains a daily estimate for loads that are intermittent and hard to estimate and which have been derived from utility company statistics. Write the name or description of each load that you have into the spreadsheet in Column 1, Appliance Description, and write the associated wattage in column 2, Wattage.

Step 3: Estimate the hours per day for each load and write this in column 3, Hours/Day.

Step 4: Multiply wattage times hours per day and fill in the Watt-Hrs/Day column.

Step 5: Finish up by adding all the figures in the Watt-Hrs/Day column.

Step 6: Repeat the analysis for a typical winter day.

These two total numbers will become the basis for analyzing the desired size of your solar panels. Contact a representative of LBA Renewable Energy Systems to discuss the significance of these electrical load calculations.