For anyone looking for a very detailed analysis of the efficiencies involved in pairing a battery with a solar rooftop system, UCSD’s Tom Murphy has an extensive breakdown of how well his own home built solar-battery combo worked out. His panels deliver 16 percent efficiency, converting 16 percent of sunlight into electricity, but what Murphy is interested in figuring out is what percentage of that electricity makes its way into his home and is used. His overall efficiency in that category is 62 percent. SolarCity is working on its own combined solar panel and battery system, most recently for Walmart, and this is clearly the dream, to pair energy storage with solar in a distributed model. It could be a total off the grid solution. Murphy notes that for grid tied utility scale solar systems, the efficiency (amount of electricity that reaches customers and is utilized by them) would be in the range of 87-90 percent, perhaps a vote that the utilities can do the battery-solar combo better than individuals homes. On the flip side for remote areas where running distribution lines is prohibitively expensive, the distributed model is much more cost effective which is why it makes so much sense for the developing world.