If you live in metropolitan areas such as NYC, chances are that you have received promotions for clean energy in the mail. After subscribing to these services, you have a clean source of electricity and gas by paying more for your monthly bill. Is there a way to get eco-friendly energy without having to pay more? If you are asking the question, solar panel unit might be the answer.   My friend and I are researching on clean household energy sources. We realize that it is easy to buy and install a solar panel unit and a battery that stores solar electricity. If you live in a house, you will…