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Solar Electric Basics
Sizing Your System

Solar Electric Basics - Sizing Your System

Photovoltaics (PV), meaning, “light electricity”, is a technology that converts the sun’s light into electricity.

Photovoltaic cells are manufactured from one of the most abundant materials on the face of the earth, silicon, which is made from sand.

Dozens of individual cells are arranged together to form a sealed, weatherproof module, these are the building blocks of solar electric systems.

Modules can be grouped together into PV arrays, and wired through an inverter that changes the direct current produced by PV modules into alternating current, making the electricity suitable for homes and business, and compatible with the electric grid.


PV modules operate best when oriented on a south-facing roof or slope, and given a clear, unobstructed access to the sun for most of the day.

After determining the electricity needs of the site, a good rule of thumb for determining the most suitable system size is 100 square feet of PV area produces 1 kilowatt of electricity.


Based on the average house hold, a 2-4 kilowatt (kW) system would meet most of your electrical needs. This would translate into a collector area of 200-400 sq. ft.

Sizing Your System

There are 2 options for calulating your energy needs.

Option 1

The EPBB Calculator is a tool featured at the California Energy Commission web site:

Option 2

Follow these four easy steps in sizing your Solar Electric system:

First to help you determine your Average Daily kilowatt (kWh) usage, please complete one of the System Sizing Forms below. You must determine your average daily electrical needs as measured in kilowatt hours (kWh). This will appear on your electric bill. To find additional information on your kWh usage you can log on to your local utility company web site, for example: or

Step 1: Gather all of your electric bills for past 12 months.

Step 2: Fill out the System Sizing Form

The Short Form applies to homeowners that have all of their electric bills for a 12-month period. If you do not have all of your electric bills for one year, then select the Long Form. The Long Form will allow you to estimate your kWh used based on the utility bills you DO have.

Step 3: Fax the completed form to The Solar Energy Company for a price quote and additional information (805) 684-1535

Step 4: Once you have determined your Average Daily kilowatt hours (kWh) you can then go to the Chart for Sizing PV System to determine which system best meets your needs.