How Google Sunroof Works

Employing the high-resolution aerial mapping used by Google Earth, Project Sunroof calculates the amount of sunlight reaching your roof to assess its potential for solar power.  It takes a variety of factors into account including local weather conditions, shade from nearby trees and buildings and sun positions throughout the year.  The tool combines this information with data from your household’s monthly electricity bill, factors in panel orientation and tilt to the roof surface to calculate average monthly and annual solar radiation, recommends the size of solar installation needed and estimates the cost to purchase or lease the hardware as well as the amount that could be saved with solar panels.

The tool is only available in the San Francisco Bay Area, Fresno and Boston, however, should Google decide to expand that coverage, they have ample capital reserves to act quickly.  They might offer serious competition to the Australian Photovoltaic Institute's Live Solar Potential Tool, which currently provides similar services.

How Google Sunroof is Changing Homeowners' Costs

Photovoltaic (PV) solar panels harness the power of the sun by allowing photons, or particles of light, to knock electrons free from atoms, generating a flow of electricity.  The electric current can power your home's appliances or be put back into the grid.  Google Sunroof has developed a tool to help homeowners assess the solar power potential of their roof.

Improvements to Photovoltaic Technology

In the 1980's photovoltaics consumed more energy than they produced over their lifetime.  Now the energy return ratio (ERR) on solar panels has improved exponentially. According to Professional Engineering magazine, the energy payback times (EPBT), the time it takes to produce all the energy used in their lifespan, is currently are between 6 months and 2 years.  And, with life cycles of 30 years, their ERR is 60:1 and 15:1.  In other words, solar panels produce 15 - 60 times the energy required to make them.

Advantages of Net Metering

Since their energy source is the sun, solar panels produce "clean" electricity, without emitting carbon.  And, many locations, including Ontario, offer "Net Metering" which means the utility credits a homeowner for solar energy that is not consumed by the home.  You send the excess electricity you generate to the local distribution system for a credit toward future energy costs. In essence, it’s a “trade” of electricity you supply against electricity you consume.