When you are ready to purchase a photovoltaic (PV) solar electrical system, be sure to check out the various packages that companies offer and the tax incentives that are available. Between loan programs that solar power installation companies may offer and the tax credits and incentives available at both federal and state levels, you may be able to reduce the cost of a PV power system by many thousands of dollars.

For example, photovoltaic solar panel systems that provide electricity for a home and that meet applicable fire and electrical code requirements are eligible for a federal tax credit of 30% of the cost up to $500 per .5 kW of power capacity. This program is for principal residences only (not rentals or second homes) and does not expire until Dec. 31, 2016.

In California, the Go Solar California program was launched in 2006 with a goal to install 1 million solar panels on homes in 10 years. This $3.3 billion program hopes to reduce the demand for energy during peak times while reducing the cost of electricity.

When you go shopping for the photovoltaic cell system that is right for your home, keep these considerations in mind:

Output
How much juice does your home need? If your power bill breaks down the amount of electricity you use on a 24-hour basis, you can easily determine how many watts your PV array will have to generate in order to satisfy your home's needs. During peak hours of the day, when the sun is highest in the sky and the PV cells can operate the most efficiently, output can range from 40 watts all the way up to 200 watts. The difference generally is in the technology, size, and price of the cells.

Dollars per watt
Another way to gauge the cost of purchasing PV cells is to look at the dollars-per-watt cost ratio. A rough estimate would be to shop for modules that are priced in the $4- to $5-per-watt range. This means that if the module has a maximum output of 100 watts it would cost $400 to $500. Using this method of calculation, you can roughly determine how much you would need to spend to power your home.

Insolation
Insolation is the term used to measure the amount of direct sunshine that falls on a square meter per day. It is rated in kilowatts and will help you determine how much energy you can expect your PV array to produce.

Mounting
In North America, a solar array must have direct southern exposure and the proper tilt to ensure maximum efficiency. There are several kinds of solar array mounting systems for the home, and picking the right one is critical to getting the most out of your investment. Directly installing the PV modules flat on your roof may be the most aesthetically pleasing approach, but it will reduce the amount of power generated during low-light, cloudy, and rainy days (yes, PV cells even work in the rain, they just generate less electricity.)

Mounting on a stand may be more practical, especially if your home has a flat or unusual roof. Some module mounting stands come with sensors and motors to automatically turn and tilt the PV cells to follow the sun across the sky and capture the most energy possible.