How to Calculate the Environmental Offsets of Solar Energy

Find the "peak" or maximum electricity rating for the solar project. Look on a solar panel for its power rating. Or ask the project installer for this information. The peak electricity rating is recorded in watts (Wp) for small-scale projects, kilowatts (kWp) for domestic-scale projects and megawatts (MWp) for utility-scale projects.

Convert a MWp figure into kWp by multiplying it by 1,000 or convert a Wp figure into kWp by dividing it by 1,000. For example, solar project developer BrightSource Energy's gross 392MWp Ivanpah thermal solar plant = 392,000kWp.

To calculate the true amount of energy the project will generate, multiply the peak rating by the capacity factor for solar, which BrightSource Energy says is 20 percent for photovoltaic solar panels and 30 percent for solar thermal projects. For example: 392,000kWp x 0.30 = 117,600kW.

Convert the kW of electricity produced into pounds of avoided emissions as such: 1kW of solar power = 2.2 lbs. of averted greenhouse gas emissions. For example, 117,600kW x 2.2lbs = 258,720 lbs. of avoided emissions.

Convert the pounds of averted greenhouse gases into U.S. tons by dividing the figure by 2,000. For example, 258,720 lbs. / 2,000 = 129.36 U.S. tons of averted emissions.