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Specializing in On & Off Grid
Solar Electric Power for
San Diego

Corporate Office:
14211 Garden Road
Poway, CA 92064
(858) 668-1701
FAX: (858) 679-7625
E-MAIL US

Products & Services Applications About Solar Power Company Profile Questions

What is PV?

Photovoltaics (PV) is the process of converting sunlight into electricity. The term "photo" comes from the Greek word "phos" or light, and "volt" was derived from Volta (1745-1827), a pioneer in the study of electricity. "Photo-voltaics" literally means "light-electricity." 

How does it work? 

When some materials are exposed to sunlight, they release small amounts of electricity. This is known as the photovoltaic effect.

This is how it works. Sunlight is composed of photons, or particles of solar energy. These photons contain various amounts of energy corresponding to the different wavelengths of the solar spectrum. When photons strike a PV cell, the energy of the photon is transferred to an electron in an atom of the cell, which is made of a semiconductor material.

With its newfound energy, the electron escapes from its normal position on the atom and becomes part of the current in an electrical circuit. When this happens, the electron creates a "hole." Special electrical properties of the PV cell, specifically a built-in electric field, provide voltage that drives the current through an external load, such as a light bulb, a hairdryer or a television set.

How much do photovoltaic systems cost?

How much you pay for a photovoltaic system depends on many factors, including system type and configuration, the difficulty of installation and available incentives. To be clear, the costs mentioned here are the installed cost. This means the final cost (before rebates) to the consumer for the equipment and labor to install and connect a photovoltaic system.

Generally speaking, the larger the system, the lower the cost. In addition, the larger the number of systems, for example a new home construction development of 200 homes, the lower the cost. 

How big should my photovoltaic system be?

There is no one right size for photovoltaic systems. Every site is different and the needs of system owners vary, too. System size depends on several factors, including how much electricity (in kilowatt-hours or kW-h) you consume, the orientation of the system, the tilt of the system, available space and funds.

The first step to determining the size of the photovoltaic system you'll need is to reduce consumption. Saving electricity is typically cheaper than generating it. Also, the smaller your overall consumption, the smaller and cheaper the system you'll need. The second rule in photovoltaic system sizing is DON'T oversize system. San Diego Gas & Electric will not credit you for any excess electricity generated on an annual basis; in other words, in any twelve month period, if you generate more than you need, the excess electricity goes into the SDGE grid and you will receive no credit.

You should try to size your system equal to or less than your annual consumption. An easy rule of thumb is to take your annual consumption (in kWh) and divide that by 1300 kWh/yr. (1kW of photovoltaics will generate about 1300 kWh per year). This will give you an estimated system size. For example, the Smiths consume 6000 kWh per year. If we divide 6000 by 1300 we get 4.6. This means the Smiths need about 4.6 kilowatts (kW) of photovoltaics to completely offset their annual consumption. 

How much electricity will my photovoltaic system produce?

How much a photovoltaic system will produce depends on the orientation, tilt and location of the system, and the amount of sunlight hitting the photovoltaic modules. 

How Does PV Work?

When some materials are exposed to sunlight, they release small amounts of electricity. This is known as the photovoltaic effect. When describing solar cells, the photovoltaic effect is the conversion of sun energy into electricity by the cells.

This is how it works. Sunlight is composed of photons, or particles of solar energy. These photons contain various amounts of energy corresponding to the different wavelengths of the solar spectrum. When photons strike a PV cell, the energy of the photon is transferred to an electron in an atom of the cell, which is made of a semiconductor material.

With its newfound energy, the electron escapes from its normal position on the atom and becomes part of the current in an electrical circuit. When this happens, the electron creates a "hole." Special electrical properties of the PV cell, specifically a built-in electric field, provide voltage that drives the current through an external load, such as a light bulb, a hairdryer or a television set.

Will SDG&E Pay me for excess electricity production?

SDG&E does not actually pay you for excess power, rather they are crediting you for the power you put onto their grid. The ability to send power back to the grid is called Net Metering. Think of net metering as a debit account. When your photovoltaic system is producing more power than your home needs, the excess power flows onto SDG&E's power grid, turning your meter backwards. This excess power is like a "power deposit" into your electricity debit account. Later, when the sun is not shining, you make a withdrawal of that power.

The bottom line is that SDG&E will never send you a check for excess power, and any electricity that you generated in a twelve month period above what you need will not be credited to your account.

Are photovoltaics cost effective?

The cost effectiveness of photovoltaics ultimately depends on the future price of power, which is difficult to predict. When you purchase a photovoltaic system, you are effectively buying all or a portion of you power for the next —at least —20 years at a fixed cost. If average long-term electricity rates are above that fixed cost, the investment was worth it. If the cost of power is below the fixed cost, the investment may not have been financially sound.

Business-owned photovoltaic systems are the most cost effective because they can take advantage of state rebate programs and receive federal tax incentives. They systems can expect to generate electricity for about $0.10 per kWh

Governments and non-profits can expect to generate power for about $0.15/ kWh While residential customers can generate power for about $0.25/kWh

How efficient are photovoltaic modules?

Photovoltaic module efficiencies range from 5% for some thin-film technologies up to 15% for single crystalline technologies. These percentages refer to the conversion efficiency; that is, of all the light that hits the photovoltaic module, the percentage that is converted directly into electricity. Conversion efficiency is a critical issue when space is limited. The more efficient the module, the less space is needed to build a system that produces a desired amount of electricity.


Specializing in On & Off Grid
Solar Electric Power for
San Diego and Southern California
(858) 668-1701
FAX: (858) 679-7625
E-MAIL US