1. How Many Solar Panels Do I
Need to Power My Home?

2. If "Power My House" means to reach net-zero electrical utility
bill, the necessary number of panels can be calculated based on
yearly usage. A generic number of panels can be determined for
an "average" home in the U.S., or a more specific answer can be
determined for your home. Another approach is to determine how
much solar energy you can produce. The later is a simple
question to answer based on your home's available sun facing
roof space.

3. Solar Panels
The commercial solar cells available today probably represent the
state of the art for years to come. Good solar panels composed of
monocrystalline silicon cells generate about 100 milliwatts per
square inch (6.45 square cm). Commercial panels come in a
variety of sizes, 100 watts and up; however, the power generated
per square inch remains about 100 milliwatts. Number of panels
required can decrease, but not the area.

4. "Average" Home
How much electricity does an average 2-story 3-bedroom house
use per day, per month or per year. The US Energy Information
Agency has estimated that the average U.S. home uses 8,900
Kwh (kilowatt hours) per year or about 24 Kwh per day. If this
average home is in a climate that will produce an average of 6
hours of sunlight for maximum power generation, each square
inch of optimally oriented panels can produce 600 milliwatts per
day.
Consequently, about 40,000 square inches (24000 watts per day /
0.6 watt hours per inch per day) or 278 square feet of solar
paneling would meet household need. If purchasing a 100-watt
panel measuring about 6 square feet, an average home would
require 46 panels.

5. Your Home
These calculations are for a fictional system but serve as a
guideline. Your energy requirements may be substantially more,
or less, than the average value used above. If your goal is to
reduce your electricity bill to zero, you simply need to know your
homes normal needs to tell you if it is possible and practical.
Electrical company invoices often show not only current months
usage, but previous months as well. On request, the company
may be able to provide a 12-month total. Alternatively, one can
take meter readings each day over a week or even a month to
include a few weekends when power use is typically higher.

6. Since usage typically is seasonable, this should be taken into
account. For most of the U.S., winter usually represents the
highest period of usage; however, in some areas of the country
summers that require maximum use of AC may represent peak
usage.
For example, if your energy bills or meter readings show that
your yearly usage is 12000 Kwh per year, a solar power system
would require a 63-panel array (47 x 12000 / 8900 = 63) of 100-
watt panels. Roof space required would be 375 square feet.

7. Resources:
http://www.getsolarprices.co.uk/solar-panel-calculator/
http://ezinearticles.com/?How-Many-Solar-Panels-Do-I-Need-to-
Power-My-Home?&id=7458783

8. Thanks for reading!