Solar

Whats nice about Google Project Sunroof is it takes the position of your house, angel of the roof(incidence angle to panels), area available for panels, and weather patterns/sun angle during the year, etc all sorts of cool stuff.

So yes, my house is all electric, but there are three very important things to consider that make quick payback difficult:
1) Electric is relatively cheap in Florida, better than most.

2) Energy efficient devices are common place now, and cheap...so the more I(all of us) upgrade to low energy devices, the harder payback will be. In the past 2yrs of upgrading, I've reduced electric bills by 45%, by nothing more than energy efficiency devices, such as LED bulbs in place of flouro or incandescent. 88% energy reduction, 10x longer life, just for lighting. And of course in Florida with the heat, every watt of energy saved(the majority being heat) is almost a corresponding watt of energy I don't have to remove with air conditioning. So a double benefit to energy savings.

3) Weather is not as nice as you might think for the Sunshine State. Yes, we have more direct sun angle in the south and lower angle roofs in general, but during the summer when the sun is brightest, with the high humidity clouds well up starting about 1:30 pm almost every day, with rain about 3-4pm. Its called the 'summer tropical weather pattern', so most days sun will only hit steadily in the morning. In the fall and spring when its drier, the sun angle is also lower so although more sun exposure, there is also less sun energy.

The best places for solar are west texas, nevada, new mexico, arizona, & socal. Southern, dry and sunny.

So bottom line, you will gain far more for the same cost of solar panels by investing in energy efficient devices and reducing power usage. You couldn't say that 10yrs ago, but I believe its true today for most warmer areas in the US.

Long ago I considered placing a rack of black painted tubing on my roof to preheat water on its way to the water heater.
To reduce chances of damaging the roof surface I figured a hinged rack that draped over the ridge of the roof and only secured at the edge of the roof.
If plastic tubing were used it would have the added advantage of acting as a fire suppression system.
A truck garage nearby burned one night many years ago. Exploding barrels of lacquer and thinner on several of the burning trucks rained flaming debris on a number of roof tops including my own. The roof was badly damaged before the fire dept finally gave up on saving the garage and began hosing down the rooftops.

Maybe the future.... Just get a solar roof instead of panels...