We’ve all heard the benefits of solar power: reduced energy bills (some states and provinces even allow you to generate power and sell it back to the grid or offer grants to homeowners), less demand on already stressed city power grids, it’s a form of renewable energy. Solar power seems so, well, perfect—if only I knew it were right for my house. Then I’d get on it right away. I would, really!

Well, this let’s-put-it-off excuse is no longer valid thanks to website Roofray. Using Google satellite data and information provided by the National Renewable Energy Labs, Roofray allows you to determine what type of solar-based system is optimal for your home before slapping down money on an actual system.

It’s pretty simple: enter your address and up pops a satellite image of your home’s rooftop. Next, using the Roofray tool, draw solar arrays and slope and, voilà—power per square foot and total peak power come up, in chart form, along with more metrics including projected performance, financial analysis, average monthly utility bill (after solar is added), total cost summary and—key, really—estimated time until the solar array is paid off.

Of course, these are all estimates, so take your calculations in stride. Also, don’t just try one size; play around with different-sized arrays and placement. Then, take what you’ve discovered, talk to some experts in your area and start earning cash – and helping conserve resources – thanks to that brilliant ball in the sky.