Calculating Daily Energy Consumption

Example 1: (Converting to 100% Solar Grid Tie from Grid Use Only)

Starting from the monthly electric bill...      
1. Record the Electric Bill Monthly Consumption. 660kwh __________ Monthly Consumption
2. Divide Monthly Bill by Number of Days in Month = Daily Consumption 660 / 30 = 22 kwh __________ Daily Consumption
3. Divide Daily Consumption by number of Sun Hours at your location.* 22 kwh / 5.5 hours = 4000 Watts __________ Hourly Consumption by Sun-Hours
4. Hourly Consumption by Sun-Hours / Efficiency Correction Factor. ** 4000 Watts / 0.69 = 5797 Watts __________ Hourly Consumption by Sun-Hours (Corrected)
5. Hourly Consumption by Sun-Hours (Corrected) Divided by Size of Solar Panel Chosen. 5797 Watts / 175 Watt Panel = 33.12 Panels [32 or 34 Panels]*** __________ Each 175 Watt Panels
* 5.5 Sun Hours might be your Annual Average. Winter Months will be shorter and summer months will be longer. For Grid-Tie it might be ok to use Annual Average, but for Off-Grid (not Metered Electricity) one should use the Winter Sun Hours to prevent a shortage of power in the winter.
** 0.69 Correction factor includes Inverter Efficiency 0.94 x Battery Efficiency 0.90 x Panel Efficiency 0.82.
*** 32 Panels can be reduced by lowering the electrical consumption of the House. For every dollar in a lower electric consumption, you will save $5-10 in the cost of Solar Panels and other equipment.


Supporting Documents

Item Description Link

Web Link

Sandia National Laboratories PV System General Sizing Tool

Hit Counter

DIY Home

Maverick Solar Online Store | Contact  2006-10

Do-It-Yourself Workshop

Maverick Solar
Help Yourself to the Sun

Copyright 2006-2009, All rights reserved.
Other Trademarks and Copyrights are used for informational purposes only.
Updated: July 02, 2010