Information You'll Need

• To be effective, you'll need a solar power system that is integrated with your regular electric utility. You'll need what your average monthly consumption is and how many solar panels you'll need to generate sufficient wattage every day. You'll also have to determine what percentage of your electricity usage you want to offset with solar power and how much sun you get in your area (see Resources). Finally, you'll need to get an estimated cost of installation from a professional installer.
  
  

Cost Per Watt

• Roughly, solar electricity costs about $10 to $12 a watt installed. Usage is figured in kilowatts. A kilowatt is 1000 watts. Therefore to generate a kilowatt, you'll pay $10,000 to $20,000 installed. A $20,000 solar electric system, depending on how frugal you are, can reduce your bill 20 percent to 50 percent. A full system for a large house can cost closer to $100,000 and require every square inch of your roof and then some.
  
  

Tax and Grant Incentives

• The government may reimburse part of your cost through low-cost loans, tax incentives and grant programs to you or your installer. Check the U.S. Dept. of Energy website, Grants.gov or your home state's energy department website or Thesolarguide.com for links to incentive programs. Do this before you buy and install a system. Many solar panel dealers can help you qualify for government help in areas where the government is promoting alternative energy.
  
  

Calculation

• From your electric bill, figure out how many total kilowatt hours (KWH) you use in a month and divide by 30. This is your average daily KWH usage. Divide by the average hours of full sun the solar panel gets per day. You can get this information from the average sunshine calculator link below. Multiply your answer by 1.15. This will give you the number of watts you need per day to generate 100 percent of your power. If, for example, you use 8 KWH per day and have an average of four hours a day of sunshine, you'll divide 16 by 4 and multiply by 1.15 or 4.6 KWH or 4600 watts. At, say $10 a watt, you're looking at a $46,000 cost for a very small solar power system.
  
  

Accurate Estimate

• Use the KWH per day number (4.6 in the above example) to get an estimate from a reputable solar panel installer as to how big a system you'll need. If you only want to replace half your electricity with solar, figure a little more than half that estimate. The solar calculator link below can give you a rough estimate too. An installer will give you a better one. Either way, until the cost comes down, count on it taking a long time for you to recover your investment.