Some possible explanations: changes in tax incentives, advertising, and weather.
Work Step by Step
There are a number of possible explanations for why solar panel installations may have increased from 2013 to 2014. Tax incentives are often provided by the government to encourage consumers to invest in alternative/green energy. For instance, the federal solar tax credit allows one to deduct 30% of the cost of solar panel installations from federal taxes. A change in current tax incentives from 2013 to 2014 may have incentivized consumers to purchase solar panels. Advertising can have an important impact on consumer spending habits. Many consumers are not aware of the potential savings and tax incentives from installing solar panels. If Sun Solar Products increased their advertising from 2013 to 2014, this could explain the increase in the number of installations during those years. A change in climate patterns can alter the economics and feasibility of using solar panels for energy in many parts of the world. It's possible that a shift in local weather patterns in some areas (e.g. more sunny days annually and less cloud cover) made some consumers think twice about the potentials of solar energy.